Don't make this mistake with your home shop air compressor | Auto Expert John Cadogan

[@dinosshed]

As an electrical engineer, pilot, plumber, mechanic, school teacher, doctor, truck driver, gynaecologist (weekends) and a professional gymnast, i must say that you nailed this one.

[@mikehunt8968]

This is why I make my own extension leads, using 2.5 sq mm arctic cable.... then I PAT them to be sure... (Portable Appliance Test) 2.5 sq mm cable is good for 20A and less voltage drop

[@AnthonyStabler]

I find you very entertaining, John. As an American, it's refreshing to hear your Aussie idioms and you've taught me a lot. My wife is tired of me binging your vids today. See you soon.

[@chazkdarwin3875]

@Autoexpert, Hi John, John Albo’s son here, Kosta. I have the same issue with the factory suppled slow chargers that come with the new EVs and PHEVs I bring home from work, as they are not my cars and I’m not buying an EV anytime soon I’m not installing a jet charger just yet. Manufacturers say not use extension cords but I do (heavy duty/ high amp one). With overnight charging nothing gets hot and no issues so far. I introduced my dad to your channel and he’s a big fan now, which is a huge compliment as he is a fan of almost no one. Lol. Cheers.

[@user-rp3lp6td2n]

Gday John, 70yr old hospital sparky technician here. 100% spot on mate. Spent many hours teaching this stuff to people for 40yrs. Great stuff thanks.

[@matt-rw6li]

If the voltage drops and the motor winding is the same ohms the current will decrease not increase like John said, your a clever sparky 😂

[@andrewgeary4720]

@@matt-rw6li sorry mate, the effect on motors is that lowering the voltage increases the current as they are constant power devices. P=VI... it's the effect of the coils in the motor that produce the magnetic flux in the magnetic circuit is what does the work, turning the motor... when the motor turns it increases the back emf in the motor , which increases the effective impedance seen by the power system. if there is not enough voltage to create enough flux, the motor wont turn, if the motor isn't turning the impedance remains low, drawing more current until the motor either burns out, or turns... This effect is why the motor draws around 7 times rated current during startup... (which is ok if it starts, but burns out the windings in the motor if it stalls, or takes too long to start, or is overloaded for too long). AjG BENG...

[@bettsy1476]

Thanks John as a sparky in a former life, still registered, I can say you pretty much nailed it for the lay person! I had my mental list and you managed to address the lot. Even the duty cycle issue. well done!

[@AutoExpertJC]

Thank you very much. Coming from you, that means a lot.

[@grantleyhughes]

First thing I did was redo all the electrical on my boat, aadd solar and batteries, and bring it up to current specs. We have to get a certificate for gas, elecrical and a seaworthy survey every five years for insurance purposes. That's an out of the water inspection too. I hate to think og how many homes haven't been looked at or have had DIY additions without seeing a licenced sparky.

[@kadmow]

@@grantleyhughes - hoe many extension cords with no tags -uggghh.. or custom replaced ends, shudder (actually the ones with bare single insulation on pulled ends much more worrying (that old cloth insulation, all frayed - lol...

[@Choober65]

I bought a reel of immersion heater flexible cable (2.5mm) to make an extension cable. Works perfectly.

[@BryanTorok]

@@Choober65 I'm really hoping this is irony or sarcasm.

[@gruffalodaddy3973]

Thank you, Sir, that was as good as it gets for a master class on electricity and compressors. I'm here in New York City, USA and truly enjoyed your teaching style and depth of knowledge. Awesome!

[@grantfrith9589]

God! I'm glad you told me I have a 40 year old shop compressor that's been operating in my shed for the last 15 years connected via a twenty foot extension cord. I better correct it immediately. I don't want to void the warranty...

[@chartphred1]

For an electrical dyslexic, numby, like me, this is a very well explained solution that many others should watch. Nicely done. Thank you 😊

[@Stevehil1]

As an electrical engineer in the uk all I can say is fantastic communication on a subject that is not well understood.

[@VFRrider]

But isn't it so much easier in the UK? Our power points are all the same, there's no thick and thin earth pins to worry about. Ring fused at 32amps radial fused at 16-20 amps. 3hp motor would be hard wired into the mains circuit. The only real problem, yet again, are humans who tend to plug anything in at any time, without looking at the fuse in the plug. The amount of power cords going to computers, table lights, battery chargers, etc, fitted with a 13amp fuse is frightening!!

[@PJ-om2wq]

We don't have shitty extension cables like that in the UK. Our plugs, sockets and extensions are all rated at 13A. A half decent welder gets pretty near to that limit in the UK so I don't know what they do down under. I put 16A commando sockets in my garage for this stuff.

[@dancarter482]

@@PJ-om2wq My _WHOLE_ workshop runs off an extension lead from the house - can't get a reliable electrician to even keep an appointment round here - gave up! I run welder/compressor and lights simultaneously through a cheap surge protection switch block - never tripped out.

[@almanzoli1736]

I really enjoyed your explanation ! I am a retired Electrical Contractor , and often tried to explain to customers the correct and safe way to use electricity !

[@PaulMappud]

The larger model of the wife's "Power Tools" has the same extension cord warning, the lights dim when it's in use, it's like a prison movie... !

[@HomeGymAustralia]

Thanks John, I never learnt this stuff my dad works in an office 😂. Love all the practical advice style videos

[@AutoExpertJC]

Glad to be of assistance mate.

[@Conservator.]

I worked in an office and I don’t understand what PowerPoints have got to do with this video. I haven’t seen a single presentation in the video. 😜

[@Thermalions]

@@Conservator. Just go talk to your WHS officer, I'm sure they've got multiple PowerPoints relating to electrical appliances and not using extension leads with them. I know ours does.

[@micktaylorwolfcreekmechanical]

John is spot on again my dad was a electrical engineer and I've worked in electrical wholesale and as a kitchen/furniture maker, I have 3phase connection to my house so its great for welders, compressors and aircon but do do tend to use smaller 10a welders and compressors more often than my bigger older ones and nearly all my power tools that my dad passed on to me have upgraded cords along with a few of them amphibian type 15a to 10a cords with a rcd or breaker in them that were home made long before you could buy them amphibian leads

[@theGreyhoundKeeper]

As an apprentice, we saw this first hand. We were working on the old Holden factory at pagewood, converting it to manufacture cigarettes. The expanse of manufacturing floors meant walls were a long distance away. We had 3 long extension leads to run a fluoro fitting to see what we were doing and if we used one of the thinner leads on aite, the fluoro would not light, instead it would just flicker like the starter was rooted. * read the ticket on extension leads too. Just because it looks thicker, the conductors may not be bigger, you may be just buying thicker insulation. Ohms law shows us that with a drop in voltage, the motor will draw more current, becaude the power consumption is a constant. The internal insulation tolerance of these devices may not handle the heat generated by the overloading of the motor windings and pop goes the compressor.

[@DaveBooth-qs7sw]

The way I see it- the compressor should be wired with a length of heavy duty flex not a cheap lead that can’t carry the current required. When wanting to use the compressor further away why not use a heavy duty lead that can handle the load! The secret is to make sure there are no coils in the extension cord or it’s not twisted anywhere in its entire length!

[@tonyonofrio1147]

Great video John. The air compressor situation also explains problems you get with extension cords in general. Like why does my power tool lack power using 100m of extension cord ? 😀 Using a voltage drop calculator and some research, I got the voltage drops for various extension cords. This might help people get an idea of which cable and length to use. For the 2.75 hp compressor, 230 VAC at the plug, and a power factor (think efficiency) of 0.95, there will be 9.39 A current draw. For every 10m length of - Standard 10A extension cords, 1mm² = 4.84 VAC drop Extra Heavy Duty 10A* and Standard 15A extension cords, 1.5mm² = 3.10 VAC drop Extra Heavy Duty 15A and 10A^ extension cords, 2.5mm² = 1.69 VAC drop Remember these numbers are at nearly full capacity (10A) of the power socket, if you are using less current then the voltage drops will be proportionally less. Half the current (5A) = half the voltage drop. * Not all Extra Heavy Duty 10A extension cords have 1.5mm² cable. Always check. ^ Only found Delta brand had 15A and 10A, 2.5mm² extension cables. There may be others. Calculator I used - www.jcalc.net/voltage-drop-calculator-as3008 How much voltage drop can you have? The allowed voltage at the power socket in Australia is 216 VAC to 253 VAC. If you get the average 230 VAC at the socket then you shouldn't have more than 10 VAC drop, giving you 220 VAC at the end of the extension cord. So for close to 10A draw from the power socket with 230VAC or more - Standard 10A extension cords, 1mm² = max 20m extensions Extra Heavy Duty 10A* and Standard 15A extension cords, 1.5mm² = max 30m extensions Extra Heavy Duty 15A and 10A^ extension cords, 2.5mm² = max 50m extensions Again if you are drawing less current you can use a longer extension. Standard 10A extension at 5A = max 40m extension. One last thing is you may need to factor in the distance of the power socket from the meter box. That length of wire will also have a (smaller) voltage drop that will affect the total and your extension cable length. Hope this helps as guide.

[@bpj1805]

The allowed voltage drop in the run from the meter box to the socket outlet is already subsumed in what you quote as the allowable voltage range at the socket outlet - 216-253V. It certainly is in my country, which I expect substantially borrows from the same IEC standards as yours. So as a user of an electrical installation, you shouldn't have to worry about that. (But your electrician who installed it, should have.)

[@chrisforgan731]

@@bpj1805 yes for fixed wiring it has been calculated. BUT for extension leads it has not. our nominal voltage range is 220 to 250 volts. most will read around 238v rms at the outlet under no load conditions

[@BryanTorok]

The thing that both you and John overlooked is that electric induction motors draw 3 to 5 times their rated running current when they are starting which drops the voltage even more. Granted, this is only for a very short period of time, but it does need to be considered.

[@tonyonofrio1147]

@@BryanTorok True. Looking at the instructions for the Stanley Twin Stack Air Compressor , the compressor has a rating of 2100W, around 9.5 Amps. It also states Minimum Generator Size of 5000W. From this I would surmise that the peak (startup) current could not be much more than double. Otherwise the generator would stop/stall or a mains breaker would trip. There may be a soft start circuit on the motors to reduce the startup current.

[@BryanTorok]

@@tonyonofrio1147 Typical (not inverter) generators have a peak (short term) rating of 20% to 25% more than the constant running current in part to allow for motor start up current. Inverter generators are not that generous.

[@dandeeteeyem2170]

As a sparky, I'm thoroughly impressed with your knowledge of 'lectricity theory & regs in 'straya. You even call them GPO's! Great video, dude.

[@AutoExpertJC]

Thanks mate - I fall over at 'inductance'. (I know what induction is...) kVA vs kW is also a grey area for me. The stuff in this video was pretty basic - all homeowners should know it. Appreciate you watching.

[@spikeuss1531]

​@AutoExpertJC To John, was so right. As you explained so well, as being as ex spark, most wiring in most wire in most home in Australia is 2.5 cm for 10 GPO outlets But most new home have 4 or more power outlet in each room. As I put out to most poaple, the RCD can up have to 20 point points. That just to start with and all doubt power point points. It doesn't stop there, as many have power points for the computer,, modern, print er and got into 6 outlet powerboats. That's not for study, but as well for lounge room the TV, top box and sound system. As you have kitchen microwave most of them 1200 watt, dishwasher , and exhausted fan. So most homes have 10 RCD and about 6 MCB for air-conditionings, hotwater service or heatpump now got RCD as work like aircon. As you was say you have 20 RCD with MCD. As most have 10 RCD for 2.5 cm wire. I have never been to you place, but having 20 Rcd on each breaker you most 4cm and had good electrician do wire. As most outdoor use 4cm wire, as light and power is on same cable. As you must have 40 power points or storage home. I read enjoyed your video. As love you to show why extreme come didn't color for different jobs. As one of your pet hates caravans using them in poaple back to live in. So can buy a RCDMCB cord so they kill them self or others. If you mind me asking where you got RCD cord as the old box type with behind power points Cheers Bruce. I miss motor writer like you John from wheels and long passrd Wayne cantell . I don't waste money on wheel or motor

[@dieterkoch8414]

Arent double GPOs though rated to 10 amps per socket... I think thats the only mistake he made

[@jemijona]

@@spikeuss1531 You forgot the hair drier, and some portable electric heaters, pulling close to 2500 watts each.

[@EricBanner571]

John, you may also consider doing a video on the maintenance of home compressors or lack there of. Plenty of DIY'ers fail to remove the moisture from the tank after use and after a few years the rust in the tank can cause a huge explosion similar to a bomb going off. take a look kzbin.info/www/bejne/qZ7Cd31shcanaqs

[@TheReal1953]

Not sure what the "explosion" is all about, but yeah, moisture left in the tank will eventually show up under the tank as pinhole leaks.

[@EricBanner571]

@@TheReal1953 You should google "compressor explosion". Once the rust has compromised the tank, the pressure will build up in the tank and then the tank lets go.

[@TheReal1953]

@@EricBanner571 I would think that's a function of a humid environ and poor maintenance. In all the yrs around compressors and dumb people, I've never seen this occur. What I DO see is tanks starting to leak at the bottom because of trapped moisture.

[@VinceA-jq6ds]

Wow. Um, don't most compressors come with a manual that explain this? Or am I one of the few 'wasting time' reading manuals?

[@TheReal1953]

@@VinceA-jq6ds About the "explosion" potential or draining the moisture from the tank?

[@karney44m]

You are spot on, every point, and a well explained video for the layperson. Sadly induction motors are very sensitive to voltage drop and this advice carries equally through to things like brick saws etc. Universal motors like grinders and drills are immune to drop, other than a reduction in speed and torque of course. In the real world, these compressors work quite happily on reasonable lengths of extension cable as long as they are at least 1.5mm and as you rightly point out, its just a 400 dollar investment, not exactly world shattering. In my own fat cave, there is a 5HP unit running from a dedicated outlet on a sub panel but I do also own a cheap 2.5HP unit and its been known to run at the end of 25 meters of half decent extension cable without any problems what so ever. The big compressor is for shop air and heavy use, the little compressor is for portable use around the farm, haven't killed a motor yet but have had many mechanical failures on the cheap units. Just my 2 cents worth, others mileage may vary.

[@AFutureOf]

Great explanation of the challenge - loved the visuals for thickness of wiring. Good prompt too that the issue is your house catching fire BEHIND THE WALL

[@Jake-ug6fk]

Without having even started watching the video yet I thought I'd share my experience with extension leads and electrics cars. I plugged my Polestar 2 into a 10A outlet expecting it to charge at atleast 8A, it was charging at 8A initially but overnight that dropped to 4A and the car was nowhere near as charged as I was expecting by the morning.. it wasn't until grabbing the extension cord (with a big sticker saying made in china and 10A/2400W on it) that I noticed it was notably warm. As it turns out, most electric cars throttle their charging current based on the voltage drop of the incoming cable to stop them setting shit on fire, this is really useful when china are selling extension leads rated at 2400W with 0.6-0.8mm^2 wire in it.

[@billharris6886]

Thanks John for all the useful comments, which I'm sure most people will find eye opening and helpful. I hope you don't mind but, I wanted to add a few comments to supplement your info. I am in the US where the mains/line voltage is 120 and 240 volts. Most low cost compressors 1.5 hp and less use 120 volts. Most of these compressors use a single phase induction motor, which has poor starting ability and is very touchy about input voltage. Rated induction motor input voltage in Australia is 210 to 250 volts but, the motor runs cooler if run towards the higher end of the range; like 240 volts. Starting surge current is about 10 times the run current so, I would highly recommend an extension cord with 2.5 mm2 wire. If the manufacturers of compressors made for jobsites really knew what they were doing, they would use a brush motor, which has has no problems running on lower voltage (except output power naturally drops). Duty cycle on these low cost compressors is about 20% so, between using an undersized extension cord and running the compressor in full sun on a hot summer day, stands a good chance of over heating the compressor if you are constantly emptying the pressure tank. Motor efficiencies can be quite poor on low cost compressors. I have seen efficiencies as low as 30% with a 0.55 power factor. Although, most efficiencies run 50 to 70% with 0.6 to 0.95 power factor. And to conclude, I guess one of the best kept secrets related to compressors is the air delivery ratings: which measures the compressor suction airflow rate, not the output flow rate as one would automatically assume.

[@volcomagain]

Make yourself a 2.5mm extension lead 🤣 As a sparky I'm really happy with John's understanding of volt drop, the explanation etc. It's perfect.

[@Paxmax]

yeeep, the piss poor copper clad alu (or worse iron!) chinesium wires commonly sold around the world today is a disaster. Discovered the hard way while building a high power UPS/Emergency power supply based on SLA batteries. The wires lost a ton of power = copper clad alu = twice the losses (and more!) than true copper wires. B'cuz losses, they also start to quickly heat up = increasing losses during use.

[@RenegadesGarage]

Auto Expert John Cadogan.. Nice video. New subscriber here.

[@Piasecznik72]

One thing I would mention is that electric motors often found in air compressors have big initial power draw. It may be rated 10A and drawing as you said 9A during operation, but at startup, they could draw up to 7 times rated power. So not only you should refrain from running it via extension cord but if you do, do not plug anything else to it. Especially any electronic devices.

[@chriskennedy7534]

True of most electric motors, compressors in particular as cutting back in under load compared to the cold start from 0 psi/kpa

[@Piasecznik72]

@@chriskennedy7534 It is true for induction motors even at no load. Just startup time is quicker but peak startup current remains the same on both load / no load cases.

[@chriskennedy7534]

@Piasecznik72 Do you think an AC compressor would agree? In rush can be tricky to measure, easy life = happy

[@Piasecznik72]

@@chriskennedy7534 Nothing that basic oscilloscope could not handle :)

[@chriskennedy7534]

@@Piasecznik72 I'll give you that, based on my limited oscilloscope experience, that's a wish list item. But compared to the multimeter owners group, only one of mine can delve that deep, including a couple of watt meters

[@rustyold55]

Thanks. Love this video John. 1976 I think it was I got a call. "The refrigerator you sent us is not working and our beer is not getting cold". Ho hum it was working fine when we pre trip tested it yesterday. So off I go and low and behold there's our perfectly good refrigerator with a 30 metre lead connected to it still wound up on the ground with the sun shining directly on it. Lots of other stories like this especially to keep the beer cold in my army days as an electrician. Enjoy your videos but a little hesitant to leave comments as my grammer is not that crash hot. Russell.

[@AutoExpertJC]

Thank you very much, Rusty. Apart from it being 'grammar' I think you did very well. 9/10 mate. I get what you're saying about the war stories from the great unwashed...

[@georgescott6967]

... and "lo and behold"! I didn't notice any problems with your grammar. Punctuation is great, 99% of spelling is good, great capitalisation, even have paragraphs. What's not to like? You did a better job than most of the commenters I see. More than 9/10 from me.

[@tonyjourneyman1944]

I'm slowly building up to a decent work shed. I bought a fixer-upper house and over the past 3 years i've found it's better to do the work myself, hence the tools getting purchased. This has extended into doing my own mechanical work with my car and motorcycle. I just bought a torque wrench last year, and my next purchase is going to be an air compressor. So, perfect timing in the last two videos from you. Thank you.

[@CGT80]

@@BlondieHappyGuy Old air compressors are some of the best. Mine is at least 30+ years old and the other one is a 1947 model. I rebuilt the 1947 model pump and bought a new steel tank, without epoxy lining. Epoxy can help the rust. My auto drains are tied to the pressure switches. The tanks drain the water every time the pump cycles and only when it actually runs, so I never have to think about it. The newer one has a rusty tank. Explosions are rare and usually they just leak, but I have considered replacing the other tank. Check out the Garage Journal Forum, if you haven't already. It is for guys like us that DIY, are pros, and do mechanical stuff. I am a pro in multiple trades so stuff like the electrical talk is old news, but it is all true and relevant and garage journal has been a great resource to learn more, especially about equipment. There is so much information on air compressors, bench vices, and anything else you can think of, from people from all over the world. Cheers!

[@Daniel-lk3sy]

Yeah you would want to use a heavier cord rated for the amperage draw of the device you're using at least something a little higher to give you a cushion so you're not endangering the plugs cuz the plugs also will be your main failure cuz I've seen it before we're yet the device said it can handle 15 amp draw but I seen the plug slowly change color on the wiring in the coating that was on the plug going from Gray to a brown and becoming extremely hard and it was only carrying just the maximum limit! On that extension cord so I always recommend to have a cord that can go higher amperage than what you're really needing so you're not blowing up your plugs

[@chrisbull2448]

Its always fun for the whole family when physics gets in the way of convenience

[@AutoExpertJC]

Yeah. The facts - so pesky.

[@davidrice7740]

The longer hose also gives more air capacity effectively increasing your tank volume.

[@Sydneywide1]

@@davidrice7740 Very cool unintended bonus.

[@petermurphy3354]

But you will get pressure drop at the device with cheap longer hoses & connections @davidrice7740

[@russlehman2070]

It gets even worse in the US, where the standard wall outlet is 120V 15A. That's theoretically 2.4 hp, but practically you can really only run up to 1.5hp motors. 240V is available, but most houses just have couple of outlets for a stove and a clothes dryer, so if you want to run a 240V compressor, you'r probably going to have to install an outlet for it or hard wire it. The good news is that extension cords of up to 12AWG (4mm^2) are readily available. Of course you need that thick, expensive wire if you're running significant power at 120V

[@RAF122s]

Don't forget, you throttle down your air with smaller air hoses just like smaller diameter electrical lines. So, while the coiled flex hose is handy it reduces the pressure you can supply to your air tool. Your couplers can also reduce the flow possible as well. So keep that line as big a diameter as you can as long as you can. First point you reduce the diameter you reduce the potential pressure everywhere past that point.

[@stevecooper2873]

Well, pressure while flowing, yes. When all flow stops, pressure will equalize. But point taken.

[@kellyvcraig]

It's a bit like running fire hose. You may have to put 180 PSI in to get 150 PSI at the nozzle. The same concept applies to dust collectors in wood shops and even home heating and cooling systems.

[@billharris3650]

Oh hell yes. I sell plasma cutters which require a certain flow rate (185 - 230l/min) at 90 - 95psi and so many customers run 20+mtr x 5mm air hose and wonder why their cuts are slow, the parts don't last and the plasma faults out. That's if they have bought a big enough compressor to start with. I have a customer that I sold a CNC plasma table to with a 105amp plasma cutter, he has now bought 2 home handy man compressors and it still won't work properly. I wonder why...

[@neilthomas649]

You have touched a very interesting point: GPO with a 10amp rating protected by a 20A circuit breaker! A sure recipe for a fire death! As mechanical engineer i have had stand-up fights with my electrical counterparts and I thiink regulations must be updated!

[@davidbrooks9576]

So you'd like one 10A gpo per circuit on a 10A breaker? So maybe 20 power circuits per house instead of 2?

[@jemijona]

This is only for domestic sites. My understanding is all GPOs in industrial sites must have their own individual breaker. There is a formula to use for domestic sites that specify how many GPO's can be hooked up to each 20 amp breaker. It is too complicated to detail here.

[@neilthomas649]

​@davidbrooks9576 The way I see it, the number of circuits on a circuit breaker is irrelevant. What is important is the current capability of what you connect to the circuit. If the internal wiring of whatever you plug into the circuit, including the socket outlet, is less than your 20A circuit breaker, you are setting up an ideal fire risk!

[@christopherparsons3271]

Another great video John. My local hardware store sells 15A extension leads (1.5sqm) but with 10A plugs which gives another option to offset potential voltage drop without breaking the bank.

[@chrisforgan731]

yes so called trade duty leads. many builders hardware and tools shops have these.

[@hydro2wheel]

FWIW, I live in the U.S.A. Many years ago I bought a 120v MIG welder. I needed an extension cord for it so I added the matching 15A male and female ends to a 50A R.V. extension cord. Yes, if you tin the wires you can fit them correctly into the terminals without fraying. I also use this cord for a more recently gifted 120v air compressor. In the last 15 years of use I have never had an issue with either the welder or the air compressor.

[@stephenshields1662]

John, i enjoy these tools and workshop safety videos more than car reviews. You straightforward descriptions are excellent.

[@JonathanMcDonald]

I have installed dump valves on all but one of my pneumatic outlets. It saves a lot of time not having to turn the outlet off then bleed the air out of the hose before disconnection from the outlet or the potential damage to a person's hearing. Love your videos. Also I'm 99% sure you can pull 10 amps max from each side of a double GPO unless limited up stream by a circuit protection device.

[@alanhilder1883]

Generally that double GPO is feed by a 16 Amp CB ( or if rally old rated for a 13 amp fuse wire ) and usually that circuit has more that one outlet fitted. Most 15 amp outlets are also protected by a 16 amp CB but no other outlets on the circuit. The wire is rated at 20 amps if 20 meters or less from the CB. Long run, up the cable size. ( yes, 20 meters CB to GPO plus Ext lead( whatever length ) exceeds that rating ).

[@bpj1805]

@@alanhilder1883 If there are other outlets on the circuit it just means the fuse or circuit breaker trips sooner if they (the other outlets) happen to be in use at the time.

[@ShadowVonChadwick]

All good points. I always recommended a dedicated power circuit to the garage/workshop as a bare minimum for a customer who did a lot of home handyman stuff. And if they weld or run large compressors, a 15A outlet which are a dedicated "single outlet" circuit as you may already know. Otherwise, the house circuits can run past the kitchen or laundry before it got to the domestic garage. Mums boiling the kettle or making toast, washing machine or dryer is running, while your handyman compressor is trying to start up, you see where we're going here. I always made shore kitchen and laundry were on different circuits too. Not all electrical contractors do. Deregulation did lower the quality of installations & construction work in general, so I observed, even in top end projects. Another issue can be the corroded or tarnished prongs on the male plug top. I personally would clean mine with a bit of plastic scourer occasionally. Can't do much with the female or GPO except replace them if they are running hot or even warm. I was an electrical contractor, retired now, and worked a lot with my brother who was a Licensed Builder. We were old school and did good work. A bit hard to do so in latter years with so many dodgy contractors around. And then took to doing remedial type work around the eastern suburbs of Sydney in latter years, paid better except for the driving & parking issues. Sorry for the ramble....... Cheers from Brissy

[@VinceA-jq6ds]

Being a scientist I fully understand the physics from a classroom perspective. Thank you translating this to the real world. I often wondered why no extension cord and your explanation makes perfect sense. You are also funny in your delivery and makes it even more enjoyable!

[@motouno3778]

Great John , easy to follow for everyone.... well maybe except for Albo ! He's still struggling with his 27 pages ... oh I mean 1 A4 page sshh sorry Albo did I let the NO out of the bag 😂😂😂

[@mgunning7362]

I've got a problem with your comment that "the motor current must increase as the voltage dropped". Youre using the P=IxE formula in a way assuming P is fixed. Its not. You must factor in thats its no longer a 2Kw motor when supply voltage drops. The 2Kw is a name plate rating only assuming supply of nominated nameplate voltage. I think if there is rise in current it would be due the drop of rpm as the rotor and stator are getting out of sync due to the loss power supply. Another factor to consider is starting current. Usually about 4 times FLC. Getting the started thru the 1mm ext cord is a big issue. When your 5 amp motor sucks 20 Amps at kick off. Your explanation of house wiring and ext cords is top notch. Dont forget HPM has 2.5mm ext cords as well.

[@rossatkinson3160]

If you are going to make assertions, as you have. You better get your facts correct next time. Start Current on a standard Induction motor, (single phase) with capacitor start, is closer to 7 x FLC. P is determined by demand, P does not decrease as voltage drops, A increases as V drops, this is why leads cook and motors trip overloads, whether they be manual restable or auto resetting thermal overloads. Again, P is determined by demand, especially for a positive displacement pump, which is what a compressor is.

[@chriscarley4335]

Hi John love the video Approved Electrician from the Old Country now living in 🇨🇦 one small point cable sizes are in mm/sq not sq/mm there is a difference . Keep up the great stuff

[@Hoop-pi6dp]

Awesome explanation as always JC. I have used a 20m, 15amp lead with 10amp plug daily as a chippy for 30yrs on a good old Aussie made Pilot belt driven air compressor with no dramas. (1650watt motor) I have it bolted inside a tool trailer, so it is a bit of a job to remove and is a two man job to pull out and carry to get close enough to a GPO. We find the belt driven type compressors start up a bit easier than the smaller direct drive units on cold frosty mornings when the air is cool and dense, but the downside is it always lives in the trailer.

[@alanhilder1883]

Just don't coil up the excess lead somewhat neatly, that will cause massive problems. I was working near some boilies using one of those small, lightweight welders ( not the problem ). The boilermaker was complaining that the welder was playing up. I had a look. The welder was near enough to plug into the gpo ( powerpoint ) but they were using a ext lead, ( 15 a rated cable ) coiled up neatly. That lead was getting quite warm. Plugged the welder in without the ext lead, worked great.

[@NatesToolbox]

And I’ve been using my belt driven 15amp plugged air compressor for 20 years on 10amp GPO’s with 10amp extension cords without one issue and it never gets remotely warm 😂. 🤫

[@Warpedsmac]

Yes but the Pilot is a PROPER tool with a motor with a proper starter capacitor circuit etc....The compressors Mr Cadogan is reviewing are not well designed and have great internal inefficiencies.

[@NatesToolbox]

@@Warpedsmac ooh this makes absolute sense to why I’ve always had zero issues skirting around technicalities because I generally always buy the best quality tools I can. Sometimes you just forget how much average, cheaper quality stuff there is out there on the market that cannot be compromised.

[@Hoop-pi6dp]

@@NatesToolbox Yep, we use various direct drives as well and like you run fine on extension leads, except some brands won’t start up on cold frosty mornings, but then they are light enough to pickup and plug into the meter box and all good.

[@grahamparsons1070]

Thanks John while I haven’t ran a extension lead to my compressor this really broke down why you shouldn’t. Appreciate it 👍

[@Chris_Grossman]

Besides the gauge of the wire, the condition of the connectors matters, especially at high current draws. Oxidation on the metal surfaces of the connectors will significantly increase the contact resistance and cause heating of the connector and voltage drop (that Ohm's Law thing). You should have mentioned that another issue with the use of extension cords is the increase the number of inline connectors. I clean or replace the connectors on my power or extension cords whenever the metal no longer looks "shiny." If I have any question about a power receptacle, I just replace them. There are cheap and much less expensive than fires. The power cords an many things are in my view inadequate. I would just replace the wimpy cord on the longer one of thicker wire gauge installing a proper wall outlet was not an option.

[@CGT80]

just use a surfacing disc on the conductors, if you can. At least that is what I do on 50 amp 250 volt plugs for my heavy use tools, in the USA. Even common 15a 125v ends aren't exactly cheap now, but I agree that if they are bad, it is no good. My dad taught me as a kid that wire size mattered, so it has never been a problem, but most people don't know any better.

[@LetGaiaLive]

I didn’t know about this issue, but I could fill books with the things I don’t know! Great video.

[@aceroadholder2185]

Good advice to avoid extension cords. If you need one for a fractional hp motor like a Dremel grinder, make up a cord that is sized for the load and make the cord as short as possible. 2 or 3 meters is often enough. If wire size needed is in doubt, bigger is better. In the home workshop it helps to plan power needs against the power available. In my shop here in 'murica I run all 110/220v dual voltage motors wired to 220v to reduce the amperage draw. Think about what you have running at one time to avoid overloads. Watch the movie "Apollo 13" to see how this might be important.

[@johnburke5384]

Wow, I watched this video on the very day my new compressor arrived....haven`t even unpacked it yet ... After watching I am a much wiser person ! Brilliant video beautifuly explained Thank you John

[@philscott7949]

A tip from another content provider who had tanks explode is never buy a compressor with a seam weld at the lowest point. Internal condensation will rust out the weld faster than sheet steel.

[@marsterofnotrades]

The greater problem is that the tank being made in a certain country to specifications totally inadequate and very very little safety margin, not that the seam is in the bottom of the tank.

[@BrainHurricanes]

Are the ends not welded all around, so there is always a weld at the lowest point ?

[@TheSilmarillian]

I had never given much thought to my air compressor you have burdened me with having to think on what you explained ,great upload indeed thank you

[@darrenwilkinson1742]

Hey John, spot on as always on the physics. I worked supply festival power through my 30’s and I’ve given this same explanation to so many mobile caterers over the years. In actuality a solid 2.5mm H07 rubber flex extension cable should be a standard issue in any fatcave, and using something like that would never be an issue, but I get your point on the warranty adherence. I’d like to see some more shade thrown at the manufacturers though who could easily use 1.5mm (or better, 2.5mm) for their cords and give people at least a few meters…. But then there is the issue of some Darwin Award contender coiling said long power cord! That would be a useful video as it goes! Let me know if you’d want some input on that video, could help avoid some house and fatcave fires! Great work as always sir!

[@AutoExpertJC]

Thanks very much, Darren. I agree. If 2.5mm^2 extension cords (and power cords from high duty cycle appliances) were the standard, most of this would go away. Coiled extension lead (in operation) = DIY induction furnace...

[@adrianinglis5922]

Fun fact: 2.5mm sq solid conductor has a lower current rating than 2.5mm sq flex cable. This is because the flex has more strands of finer wire to give that 2.5mm sq cross sectional area and therefore more surface area.

[@sn0wchyld]

@@AutoExpertJC Not so much mate. The issue with the coil is the lack of airflow a bunched up cable has to get rid of heat. there's little in the way of inductance 'in the coil' - because the return runs right next to the live... so the generated fields largely cancel out long before they interact with anything around them. running the 'return' next to the 'live' is a common practice in AC circuits to minimise emitted fields. The coils in your induction stove for instance all 'turn' in the same direction, just like those in a motor winding. if they had 50% of the turns going the opposite way, then you'd get no flux in the motor tooth, and no induced current (thus, heat) in your pan (or wire) and therefore largely mitigated inductance in that air coil. you can do the test yourself if your willing... run 10A through 1 core of a coiled cable (use a dc power supply, for instance, no need for dangerous voltages, 5-10v will do plenty) and hold a magnet or bit of steel in the coil... you'll feel some of the electromagnetic force if you have enough turns coiled up. Now hook up the circuit such that it runs the same 10A back down the 'neutral' or 'earth' lines in the same 3core cable... you'll find far less (virtually none) of that force on the magnet/bit of iron. if you have an inductance meter, you can hook it up to the same 2 circuits, and see a dramatic difference in inductance.

[@paulwary]

@@sn0wchyld Yes, I don't think inductance comes into it to any significant degree.

[@chrisforgan731]

@@sn0wchyld many extension leads have a helix. yes at domestic supply voltage the currents really arent high enough. but get a pair of high voltage wires evenly spaced and it can. swer systems have to have isolating transformers and bonding mats to control this inductance.

[@MichaelCzajka]

Really good explanation. I enjoy the explanations more when you don't swear too much... it often detracts from the message... so thanks for toning down the language. 🙂 P.S. We use a long air hose most of the time... and sometimes drag out the 15 amp extension cord if something is really far away e.g. Painting the fence. The compressor is used gently most of the time so it usually doesn't work too hard and even a normal extension cord doesn't seem to cause much of a problem. Our compressor is now ~40 years old... and still working OK. We've only changed the oil once or twice during that time. Last oil change we bonded a lubricant to the inside to reduce the wear further. The hoses and fittings (higher flow rate) have been upgraded once recently when the old hose got a bit old: Got tired of adding connectors and stopping leaks.

[@farken7467]

Hey John, I've had the same Finnish made air compressor for nearly 30 years. Its rarely done any real hard work but it has a cord not just short but barely 50cm. I've always run it with a 5m or less industrial style heavy duty lead with a minimum of 1.5mm conductor and never had an issue. Its been incredibly reliable and is a good friend. I get a bit of rust juice these days when I drain the tank after use as she's ageing, is there anything you'd recommend to put in the tank to help neutralise the rust?

[@Shakerhood69]

My Craftsman Compressor is over 30 years old too, I drain it frequently too.

[@stevehepburn5094]

Really appreciate the explaining of relationship between voltage - amperage - horsepower. I have a 240v 6hp beast, and I parked it 5 feet from my breaker panel in the garage and ran the dedicated 240v 20a outlet so I can use the factory lead, which by the way, seems fairly thick and robust. The one aspect you didn't mention is volume and pressure drop if you use gimpy air hose over long distances. I have 3 20 foot hoses, and I only use as much as I need to reach where the work is. The other option is to run pipe and have outlets along the way so you can have full air delivery a fair distance from your compressor. As you said, an air nailer doesn't put much demand on air delivery, but if you are polishing a car with a polisher that eats 11SCFM at 75PSI you are definitely not going to want to have 15 or 20 feet on unneeded hose coiled about on the ground starving your tool of air. Great video, and I am not one of those who wishes to prove you wrong (like you said) - because you certainly are not - but just wanted to add that aspect. Thanks for another great lesson.

[@marklittle3551]

Excellent advice for diys that just bought a compressor to play with. Also If I remember correctly start up current on most electric motors is significantly higher for a short period which is sure to heat up those 1.5mm conductors. On the subject of Albo I cant really imagine him warming up the compessor to spray the box trailer and although I dont always agree with his politics I believe his heart is in the right place!

[@alanhilder1883]

Rule-of-thumb. Motor start is 7 times the rated current. That is an unloaded motor ( eg. compressor is completely empty ) Some will draw less, some draw even more.

[@michaelslee4336]

I’ve always known it as 9 times the starting current, but not really important. We have a few 400 kW direct online motors at our plant and that’s enough to dim the lights. And they are baby drives.

[@alanhilder1883]

@@michaelslee4336 And those direct online motors will pull even more that 9 times. ( I assume you mean the load as opposed to reduced voltage starters ) Main place I've seen full load DOL starting on "Large" motors is in power stations.

[@michaelguerin56]

One of the reasons why a soft start setup can be a good thing.

[@alanhilder1883]

@@michaelguerin56 Have you ever seen a "liquid resistance starter? Or more so when it is starting?...😱 ( slight exaggeration )

[@solarfunction1847]

@Auto Expert John Cadogan Also a lot of ppl don't understand that all motors that routinely start up & shut down like compressors are designed to do the start up in rush current is sometimes 4x to 8x the amount of current drawn for continuous use. This can be quickly noticed when using DC to AC inverters that need to provide around 8,000w to 10,000w for a 3 HP motor such as an air conditioner or a compressor. The in rush current might only be for a few seconds but if your 3 HP compressor is constantly stopping & starting then with a small wire conductor power lead that comes out of the compressor must be short so that it doesn't overheat too much with loads of resistance from having a long power cord. If the manufacturer sold compressors with longer power cords then they would have to increase the wire conductor thickness as well as the cost of the increased length of the cord to thousands of items which would cause the production price to go up heaps & taking money out of their profit. Nowadays every device is made to have a long enough lifespan to get past the warranty expiration date so that the item can then fail so that you are forced to throw it away & replace the item again. This is done to maximise profit & to make sure that the customer returns to keep buying the products so that the company continues to make profit. If a company started making products that last for 20 or 50 years then they would go out of business waiting for customers to return to buy new products.

[@IansMusical]

Hi John, On a slightly related note I'd be interested in a video regarding air compressor vs battery tools for DIY mechanic use, particularly an impact wrench. The pros/cons, costs etc. Greetings from the UK.

[@AutoExpertJC]

Generally battery for the win. But you get locked into a brand's ecosystem...

[@aslkdfjhg]

Air tools are nowadays cheap, reliable* (if maintained), scalable for agricultural or construction use and multi use. Batteries are portable, plug and play, no leads, quieter and low maintenance. Batteries are more suited for home duty and trade with passenger cars, Pneumatic still has advantages for Mining and Agricultural machines that require more oomph.

[@CAIDMASTEROFPYRO]

Battery 1000% better, air is more powerful at the high end but I've never come across something my Dewalt mid torque can't undo and if I ever do they make a high torque that is significantly more powerful again. So much more convenient, quieter, easier, Price really is up to you, the cheapest battery stuff will be cheaper than the cheapest air system but both can be very expensive if you want quality. Air tools are pretty much a lifetime tool, battery not so much but they do last a good while especially for a home gamer. I chose Dewalt because Bunnings sells it and is both close and open late, it's also cheaper and close to as good as Milwaukee which would be the money no object choice. Other people have lots of luck with Ryobi though and it is definitely the bang for buck choice

[@krissteel4074]

@@aslkdfjhg Air power has its niche in things like some industries, agriculture and mining because they work with so much stuff that can blow up given enough sparks and fire. Coal, grain dust, gasses and various vapours all can contribute to a local extinction event for the region. For the average mechanic you're probably better off with electrical for the most part for ease of use as compressors do need some kind of maintenance cycles of oil and cleaning out the cylinder sometimes. Course if you're doing very heavy work on site based machinery or large vehicles all day, air can come in handy for heavy lift jacks and stuff too. Or if you end up being the lucky prick changing about a billion lug nuts on a truck or something

[@dinosshed]

There are some things that pneumatic is the only option, battery stuff is very convenient for reducing noise and not walking around tethered. I use both, I perform many different tasks.

[@sirmalus5153]

You could do what I did some years ago now. I bought a compressor of 150ltr and it had to run off more than the usual power point in the wall to reach the blasting cabinet I made in one of my sheds. I used the cooker circuit (32amps) and a cooker cable of 6mm square T&E cable, with 32amp industrial plugs from the fuze box too the machine. The handbook rated the motor at up too 14.5 CFM and up to a 30amp power circuit, so I used the old cooker circuit with suitable connections etc. The machine has run reliably for around 8 years or more. I also do the same for my large welder, wich is rated at 7KW and up to a 30amp circuit. Not both at the same time of course.

[@keithfisk5641]

I get that you tried to keep the story short but a big issue with all single phase capacitor start motors is the high starting current that is drawn momentarily on switch on, typically 5-7 times the full load current stated on the name plate of the motor. Any excess volt drop while starting extends the time taken for the motor to reach operating speed and stresses the motor starting winding and the starting capacitor both of which have short time ratings. (If the starting time takes too long your circuit breaker will trip and the compressor won't be able to run.) These short time ratings for the motor starting components are why single phase motors are specified with a maximum number of starts per hour. If using a single phase compressor with high air consumption tools you need a compressor with a continuous run operating mode otherwise your motor will eventually die if it is repeatedly cycled on and off by the pressure switch. My solution was to make my own extension lead out of 2.5 mm sq. flex so the rate of volt drop in the lead is the same as the rate of volt drop in the wiring in the wall.

[@AutoExpertJC]

I think that's the ideal solution. I appreciate the tips about the surge on start - explains why I've never been that successful running a compressor with a battery-inverter system.

[@robertgregory8964]

Bunnings "caravan" 15A extension lead (2.5mm2) with an 11A RCBO adapter to the 10A GPO.

[@keithfisk5641]

@@AutoExpertJC The same situation exists meeting starting current requirements with electric motors supplied from a small generator. Power tools with built in electronic speed control or soft start are usually no problem but any machinery with single phase induction motors running from a generator need the generator output rating to be several times higher than the motor name plate rating for trouble free starting without undue stress to either the motor or the generator.

[@George-Edwards]

Oh how I love your videos John. As for me, interested in electrical things since I was a young child. Learned a great deal in my USAF basic electronics training before we got into studying radar subjects and then worked on a radar on Mt Hebo OR watching for SLBMs for three years. As I'm guessing you'll probably say ( I'm only half way through the video) extension cords are not a problem as long as the conductors are heavy enough. I worked for Black & Decker for 40 yrs and our electric mowers were I think 10 amp motors and were said to be good on 100ft of 16 ga wire and when I questioned that I was told that the motors were really designed for a lower voltage than what the NP specified because they knew they'd almost always be running on long ext cords. As for me, 6HP two stage 80 Gal tank, comp in the corner of the basement with air going every where I want air via 1/2" soldered copper piping. (water pipe) I can run that comp pretty hard when blowing out the sprinkler sys or if I climb up on the roof with a couple special tools I made to blow out the gutters but I occasionally go to the basement to check it and always make sure to drain the tank after it cools down to get the condensation / water out. Keep up your good work John. Mustang George

[@aslkdfjhg]

As a former Bunnings employee who worked in the toolshop and did the warrenty claims, buy the right compressor for the job. The Ozito oil free compressor is great, but not suitable for dusty environments and constant duty cycles. It's designed for pumping up tyres, balls and blowing the dust off the bench. Drain the water after every use and it'll last 20 years. If you plan on using thirsty rattle guns, working in a dusty woodwork shop or a daily driver with the air tools, get an oiled compressor with proper air filters. If you're not sure, rent one! Rent a couple, find the one which works for you.

[@adamfink5294]

In the US we use single phase 120v for typical outlets, so all of our extension cords are beefy by comparison (same power output requires roughly double the current, more current = bigger conductor requirements). What is considered a mid-low grade extension cord here uses a wire size we call 16 AWG which is ~1.31mm^2 per conductor. Your run of the mill contractor grade extension cord can use 12 AWG or 3.31mm^2 conductors (again, assuming 120v applications which I need to specify because we do also use 240v outlets/extension cords in the US for some residential applications... almost all modern US homes have 120v/240v home electrical panels). I have even seen 10 AWG (5.26mm^2 conductors) extension cords. Yes, smaller AWG means bigger cross sectional area conductors. When you need conductors smaller than 0 AWG (53.5mm^2) it then counts up as 00 then 000 then 0000 (67.4mm^2, 85mm^2, and 107mm^2 respectively) and then when we need even bigger conductors we finally start counting up as cross sectional area increases... except the unit we use is called a kcmil and it is literally the area measured in the equivalent number of 1000 x 0.001in diameter circles of cross sectional area (instead of... you know... just counting upwards directly using cross sectional area of the conductors themselves.................). So absurdly convoluted....

[@grantleyhughes]

That was a great video. Living on a houseboat and seeing what some people do for power is quite scary. We have a 15A pole and plenty of boats run a piddly little lead. Same with the lead from generators. People need to realise that extension leads have a lifespan and replace them as required. Also if you suspect power points have been installed unlicensed, get a sparky in to test it all. Still can't beat that Highway Patrol Tesla charging lead though.

[@AutoExpertJC]

It really depends what consumption devices are in the houseboat (ie - drawing 5 amps on a 10-amp lead is no problem. Drawing 12 is a huge issue.

[@wayne9518]

My compressor currently resides at the rear of the garage. Right next to an outlet. Previously it was run on a 100 ft long 10ga extension cord. It doesn’t seem to have damaged it in anyway. Extending the airline drops delivery pressure and flow when you need it most.

[@123hoffie]

Lie in bed awake and get this into your head. Once you get Ohms Law worked out it will be a light bulb moment when it'll all make sense, so useful. ( maybe not in bed but with pen, paper and a calculator ! )

[@starwombat]

True, but straight Ohm"s Law is only truly accurate for Direct Current (DC). The Alternating Current (AC) motors on the compressor are inductive loads and therefore the power factor has to be taken into account. It will not introduce a significant error, but just saying for awareness.

[@m-erko]

When I was a novice carpenter I never grasped Ohms Law well enough to remember it until I found myself staring at the label on a 4 way adaptor & had an epiphany. 240 volts @ 10 amps = 2400 watts. Aha! So 240 watts is 1 amp! So, 120 watt thing @ 12 volts is 10 amps! That sort of set the meaning of the relationship of the values for me. Being able to calculate tool & component loads relative to supply quickly is vital when every day's set up is different. To this day I still picture that label on the 4 way for a fraction of a second.

[@Gobertron]

how are they going to know if you used a ext cord?

[@jesus_built_my_hotrod]

does this mean we are one step closer to a bin cam? 😅

[@AutoExpertJC]

Several steps in that case...

[@ScottMurrayBestFamilyCars]

I was asking myself this same question.

[@fixittony]

Awesome video! Brings back memories when I worked at a tool and mold shop. They had one compressor with a huge tank. The shop used black pipe running around the shop with connection points about every 20’ along the walls, at each support column, and every machine. Hoses were kept short line 25’ or less. Keeping long hoses from Coursing around a shop floor over tables, and getting run over by jitneys improves safety issue. And which dude wants to carry 100’ feet of 1/2” rubber hose around?

[@MasterofNoneTV]

oh boy, I thought you were going to talk about how these air compressors get a little explodey when you don't drain them and get rusty.

[@AutoExpertJC]

Might save that for another day. (My oldest compressor is behind a brick wall...

[@rdoody2067]

Spot on, thanks for the valuable video. I sat down with pencil paper and calculator to determine the compressor needed and 2 hp would work safely. A friend of my complained that the 5hp compressor would not work. I tried to explain to him all of this . In America normal find 120V and 15amp circuit. Best Regards!

[@grahampurvis5160]

Good Vid.I had a much heavier gauge flexible lead that was much longer hard wired into my compressor years ago.Hasn’t missed a beat.As you say,cross sectional area of the lead is very important.👍

[@iandennis-cg1eg]

Well said John, over here in what used to be Great Britain there are many of our new countrymen that could learn a lot from you!

[@markbrzezinski8889]

John, its Mark from Perth. Forget about the cord length and amperage rating of the cable. If you vary the voltage to the compressor motor by having a circuit that can vary the voltage then by dropping the voltage the motor will "slow down" in speed because its load is constant. When this occurs each winding in the motor is subject to a "longer" pulse of current be it slightly reduced current and this will cause that winding to heat more than usual. Added to this is the cooling fan of the motor is spinning slower and cooling less which contributes to the motor windings heating up to the point that they melt or their insulation fails. It is that home air compressors are built with very little safty margin regarding thier "cooling capacity" when they run slower than normal operating speed is what makes them fail. I think you could have talked about this which would have given people a greater understanding as to why their electricial motors fail in general. I am sure many people have jamed a drill and stupidly not released the trigger and watched the motor smoke. So the one active winding is heating up and also it's not being cooled by the fan. John if you listen to what you say, you kind of suggest the resistance in the power cord is causing the motor to fail which it would not if the motor was built to tolerate a small reduction in speed that is it had excess cooling capacity. But these days things are built with very little safty factor built in. Great discussion and I have to admit I have run my compressors sometimes on long leads. You can buy 10amp plug extension cables with 1.5 or greater cables if you look around. People don't because they cost a lot more.

[@andym2612]

At tech we got told about the water in a garden hose analogy. The water in the hose is the current and the speed at which the water travels is the voltage. Crimp the hose at any point and this will create a resistance and slow the water down, this is just like a voltage drop.

[@williambennett6526]

Thank you John . How many house fires did you just prevent? Several I expect. Hats off, well done. 🥵

[@uksa007]

Yep, sounds about right, only thing I would add is that it's generally the startup current of the PEM motor where you come unstuck, as the small gauge wire can't deliver the large inrush current the motor needs to gets started and that's how the windings in the motor get burn out.

[@Sparky_D]

This is my first time watching one of your videos. As an Aussie sparky myself, I loved it. Pissing myself laughing at your humour. 😂

[@Mach141]

As your going through the multitude of options to upgrade the wiring, getting near the end, I am saying to myself "why doesnt he just tell him to get a longer air hose", which would also be less expensive. And you did not let me down!

[@cammc8502]

I replaced the cord on a 2nd hand compressor a year or so ago. I was in a hurry and used what ever cord i had handy. Although i cut it to roughly the same length i noted that it wasn't same gauge and said to myself, replace that later (Which or course i hadn't). Your video prompted me to do it and hopefully saved my compressor from a premature death👍

[@SteveBurns80]

As a sparky, I say this is all good advice, and yeah I wouldn't be concerned with using an extension cord on the odd occasion, especially on a small air compressor such as this. If you really do need more length in a permanent position, just get a sparky to replace the pissy flex lead with a heavier 2.5mm2 flex lead.

[@l.george7517]

Great presentation. Here in the US, on commercial property, we are not allowed to use extension cords for the same reasons that you noted, except for temporary, short term use.

[@MattBrownbill]

Good advice, I've always made my own heavy duty extension leads, fine for welding and compressors.

[@williamalexander1743]

Getting back to that formula you were talking about, it is E over IR, whereas E is voltage, I is current, and R is resistance. Just put the one you want to calculate on the other side of the equal sign. When you replace the lead coming out of the compressor with a heavy-duty wire, make sure you keep the original wire in a plastic bag to keep it clean in case your compressor develops a problem then put the original wire back on. The manufacturer is providing an interior cord just to save some money. If you buy an expensive tool, for example, a Bosch sander, it will have a long flexible cord.

[@doncodman913]

Hey John.. From experience the info on how the motor is rated for use is not so easy to find on buying a compressor. The compressor I had issues with was rated at about 80% . This meant it was not to be run constantly . Most people expect a compressor to be able to switch on and off as much as you need . Some manufacturers do put in the description suitable for constant running. If you dont know what question to ask you can end up with something that is going to fail. Great vid mate . Regards Don Codman

[@noahkatz9616]

In the U.S. things are more sensible; many tools come with a table telling you extension cord requirements for conductor size and length. It makes a lot more sense to extend the length at the electrical input than the air output, where you add air resistance and reduce the effective power of the compressor, and have the inconvenience of trailing air hoses.

[@jeffkesler1547]

Always learn so much from you mate. Things are a little different here in Texas but the basic rules still apply. Keep up the good work!

[@petergoodwin2465]

Great advice, i run 2 compressors for air tools. Garage has 15 amp power points especially for the welders. ..

[@cyclops1448]

Well mate, you’re answered my question about extension cords and compressors, I just get a power point put in the garage by my compressor. Blood good commentary mate😁👍😎

[@criggie]

You made a comment about topping up car pressures occasionally. So, does this mean leaving air pressurised in the tank? I've been turning my compressor off and emptying the tank while cleaning up with a blowgun, then open the drain and leaving it open when not in use. Thoughts about leaving a compressed air tank full at pressure indefinitely ?

[@troubleshooter1975]

Also the plugs/GPO are a 'restriction' too... If you feel the cord on something drawing a lot of current, and then feel the plug, you will often find the plug is much warmer than the cord in general. Just something to be aware of, and use longer and fewer extensions as possible. Hopefully only one extension cord at most, and I would never use any more than two...

[@davidmoynahan9585]

For demanding air tool use, a two or three cylinder compressor with unloading valves means the motor isn't stopping and starting frequently. In other words, buy a compressor that meets your needs. The power lead used to be like 1.5mm2, but with the cost of copper, sizes were reduced as a cost saving to the manufacture. Improved insulation also means the smaller leads can run a bit hotter without setting fire to itself and other combustible items. Interesting that the power plug blades on a 10A lead are the same size as the 15A ones, just the earth pin as you explained. Thus the 10A blades are capable of 15A (Phase/Neutral). I personally use 1.5mm2 or better extension leads (20m or 2.5mm2 for the 30m ones), one time purchase and last a lifetime if looked after. Nobody ever regretted buying quality. Great content John, as usual.

[@frankgooding443]

Great video John small point about cross section increasing flow of Amp or fluid being related to R^2 . The Radius Squared has a huge effect on the flow so a 1 square is not half a 2 square cable.

[@chriskennedy7534]

Fascinating how science now suggests more energy travels around the wires, than through them, Def not the case with the liquid analogy

[@davetaylor4741]

Professional carpenter for 42 years. For a lot of that running compressor on the back of my ute. About the biggest 10 amp you can get as a portable. When framing often running 2 to 3 hoses off it with framing guns. Compressor stays on ute running off crap Bunnings leads. Current compressor over 20 years old. Never missed a beat in all that time. Sometimes if power source is temporary pole it runs off two leads joined together. And on the odd occasion has run on three. The only time I have known a drama with running off a lead is with 15 amp compressors. Sometimes even on a 15 amp lead they can struggle. But 10 amp. Nearly every tradie I have worked with used to run their compressor off an extension. 15 amp house sockets are wired with 2.5 mm the same as 10 amp sockets. Usually with a 20 amp fuse. The only difference being the number of outlets in the series. There used to be a limit, of how many 10 amp outlets on a 20 amp fuse. 10 I believe. But that is not the case anymore. So potentially you can have several appliances all drawing power at the same time on the one fuse of 20 amps. With the 15 amp. Same wire Same fuse but not multiple outlets. So running your 15 amp appliance from a 10 amp outlet not a problem if there aren't other appliances being used concurrently. Not many homes have a 15 amp outlet. Which often necessitates using a 10 amp outlet for a 15 amp welder etc. Just be careful what else is running as well.

[@sa4555]

And that is why I love John, not just for his razor sharp sarcasm but putting things into perspective. Now I put my compressor right next to the GPO, that is completely isolated and was initially cursing the manufacturer for only giving us 1 meter of cable, i did thought several times of extending the length of cable or add extension wire vut never got to it. Guess my laziness saved me from doing something dumbass. Now please do a video on maintaining an air compressor both oiled and oil-less motors. The manufacturer claims it maintenance free but last time my ex mechanic told me that transmission oil of my BMW doesn't need to change, I paid through the nose for a replacement of the whole thing, so I beleive nothing is maintenance free. Thanks John.

[@levif.1145]

The "bad" cord you shown 13:30 is not the worst, the market is flooded with 0.5 mm2 and 0.75 mm2 wire cords rated for 10Amps. I actually measured the wires in one, and they ware ~ 0.38 - 0.4 mm2 and rated of course for 10 Amps. Gone are the days of 1.5 mm2 wired cords rated for 15 Amps that everyone considered junk.

[@gazzas123]

That we explained so well. I use a long air hose that reaches all the way around my workshop and down the drive to the back of my ute

[@psylenced]

Wondering if you did do the multiple cable trick that you mentioned, putting a watt/power meter directly on the GPO, and then a second time putting the meter after your 15a cable and measure the actual 2 voltages. If you're still getting 215-220 out, it should be fine. If you're getting 190-200 on the power meter, then you know the voltage drop is likely to cause damage.

[@dkphill]

Thanks John, kinda didn't want to watch this video as i knew how to operate an air compressor, however I was bored and watched anyway and I learned a few things that I did not know. I always knew that volts x amps = Watts, but I did not know that power = volts x amps (i guess power and Watts are the same) and I also learned that 750w is equal to 1 horse power. You make great content, always found you both educational and entertaining, I also bought a kia sportage after watching your review. I got the 2.0L crdi kx-4 awd auto and love it.

[@alanreilly9056]

Hi John, thank you for posting this. At home I have a 240volt / 15amp outlet in my garage which I run my compressor from. This outlet has it's own circuit breaker in the fuse box I am running a Mc Millan MC15 triple cylinder compressor ( maybe a bit of over kill for a home compressor use, but I got the compressor at a very good price at the time ) the compressor motor is rated at 3 horsepower, with 16.8 CFM displacement. I also use RYCO quick release couplings on the airline

[@CGT80]

No, it isn't overkill. That is only 11 cfm and probably at something like 125 psi. Displacement is always higher than actual cfm and 17 actual cfm is 5hp size and 3hp is around 11 cfm. At least it is better than a lot of portable units and you have a dedicated circuit. My home shop is 17.3 cfm at 175 psi and averages 20 cfm from a real 5hp baldor motor that weighs 109 pounds with a 1.375" shaft. I had an 11 cfm compressor and it was better than others but not nearly enough air. A blast cabinet and plasma table to cut up to 3/4" plate requires much more, as well as die grinders. I think 5hp and 17 cfm is the minimum if you use power hungry tools, for a single person. I don't need more, but more never hurts. The old 5hp motor requires a 240v 30 amp circuit at minimum so it is on a 50a circuit which is common for welders as well. My big compressor is an awesome old unit that was built by westinghouse for train brakes but was used in shops as well. $700 used was great where a new unit that is pressure lubed and of the same quality would be $4,000 to $5,000 easily.......most small (under 10hp) compressors do not use oil pumps.

[@scottnever8732]

kinda new to this channel, so far loving the straight talking Aussie. I'm from the UK 😂

[@kurk1701a]

Really liked the "Aircomressor's /ohm's law for dummy's " full of facts,very informative, easy to follow and understand. Great tutorial 👌 👍 👏

[@Thamian]

Something else to bear in mind with extension leads (not sure how much of a thing they are in Aus though) is that extension reels present their own problems: Extension reels (or any coil of conductors) are effectively massive inductors - they will heat up just from the inductive reactance in the coil, never mind the resistive losses. As they heat up, the less current they will be able to handle, the greater the voltage drop, the more current through them, the greater the inductor effects and so on So if using an extension reel for anything more than say 8A @ 230V AC(strictly rule of thumb, hotter environments you'd probably want to go lower), pull the whole lead out of the cassette/off the reel, because otherwise, bad things can happen. Going further, and for the really big stuff, you'll also want to lay the excess in a figure of 8 configuration - the way the magnetic fields flow around that form hacks down the inductive effects to negligible - used to have to do that for 32A+ cabling for stage electrics, and typically did for the 16A stuff as well if it was piled up under a stage rather than hanging in open air from the rig.