How to troubleshoot the transformer

[@andygeibe]

Just started school for hvac. Awesome to have your videos to help me understand what I learned in class

[@grayfurnaceman]

That's what they are there for. GFM

[@Boojyman]

How's the career going ?

[@r4ym1n13]

HVAC student here about to graduate. i have been obsessed with your videos for hours now. great videos

[@grayfurnaceman]

Thanks for the support GFM

[@jefflynn4079]

Thanks. The ohms test helped me diagnose mine and determine I had a high voltage issue. New transformer installed and my a/c was back to work.

[@kalimanx]

Thank you for this lesson. Good job on explaining the troubleshooting process.

[@gdub14]

Great video. Thanks. I was getting no voltage out, but wanted to verify it was the transformer. My primary had failed, like yours

[@mitchd949]

Truly excellent videos, grayfurnaceman! I have an older RGDC Rheen gas furnace from the 1980's (I'm in SoCal so furnace literally only runs 10-20 hours per year). While cleaning the burners last week, I broke the tiny tube on the mercury pilot switch that is part of the ignition module (SP710A). Of course those switches are no longer made so I installed a modernization unit from Robertshaw. All seemed well but then the transformer failed on the 24V side. Based on your vids I investigated all wiring and connections. I replaced the fan unit (only $40 for the unit including transformer and relay that bolts to the 4x4), and I also installed a 5amp tiny circuit breaker on the hot (red) wire as it comes out of the secondary side of the transformer. I can only speculate that the wiring shorted against the chassis - because all I did was re-do all wire nuts related to the new ignition module including addition of electrical tape. I verified about 26V voltage and about 0.6amp current. Your logical approach to troubleshooting helped me to think about these things and the furnace is working nominally now!

[@grayfurnaceman]

Sometimes you never find out. GFM

[@grayfurnaceman]

Generally, transformers fail from shorts in the system or overloads from things like contactor armatures sticking. The transformer itself is very dependable. GFM

[@EddieLeverich]

Usually a short in the system if you find a blown transformer and some shorts can be a pain to locate

[@grayfurnaceman]

Opps, I did not follow up on that one. Thanks for the reminder. I will be doing that one probably tonight. It will be also located on the "control transformers" playlist. GFM

[@grayfurnaceman]

Take a look at "How to replace a transformer without blowing up the new one". And you are right, transformers seldom fail. Thanks for the comment. GFM

[@joex110]

Great vid but it would be helpful to put a link to the next video either on the screen or in the comments

[@grayfurnaceman]

Thanks for bringing this up. Some of my older videos had links no longer supported by youtube, so they were just dropped. I have fixed this for this series of videos. GFM

[@realSamAndrew]

What is a normal resistance reading for the secondary contacts? I was troubleshooting a thermostat issue and checked the secondary ohms before switching back on and got around 1.5 ohms. Thought it was shorted so I didn't switch back on for fear of frying the board or something. Now on hold till I can investigate.

[@grayfurnaceman]

Your 1.5 is probably normal GFM

[@louisviciedo]

I just moved into a new home and want to instal an ecobee. I went to the transformer and only have 1 segmenet of 24v through the RED secondary, the GREEN secondary is grounded and doesnt have constant 24v. The GREEN wire is connected to my BLUE C wire. the result is that Im not getting constant power to my thermostat C wire. Is this a wiring problem?

[@bigshotcruz9677]

What’s that white board in the back called the one with the holes

[@antonetrinh8662]

This video will eliminate lots of service call. Great job.

[@grayfurnaceman]

Thanks for the support GFM

[@teamunicorn9389]

Antone you starving a lot?

[@grayfurnaceman]

As transformers seldom fail, I would guess there is a problem with the board that is causing a short. If the board changes the low voltage power to DC, the diodes in the rectifier could have shorted. You can look for bad solder joints on the components if the board just does not work, but if it is shorted you would need knowledge of semicouductors. Hope this helps. GFM

[@caru3257]

I had a transformer blow up on me because it was wired through cover. I replaced it and went to work outside and the compressor was dead.

[@grayfurnaceman]

@@caru3257 If you are asking if there is a relation between the transformer failure and the compressor failure, they are probably not connected. GFM

[@sgtbigtoe7640]

I recently replaced the contactor on my goodman heat pump/ A/C out side unit, the contacts were melted together, I replaced the contactor and the heat pump worked again while the weather has warmed the A/C wasn't coming on after checking many possibilities I gave the transformer a smack with a screw driver and it's started working again, hopefully for good, not sure if that was the cause or I just wiggled the right wire some where

[@grayfurnaceman]

Probably only temporary. GFM

[@macster1457]

can I test the voltage of the doorbell by removing the outdoor button and using a multimeter on the 2 wires?

[@oneshoe123]

Great job,I thought your video was very easy to understand and follow. Now I'm not afraid to check mine because you gave me knowledge, Thanks

[@grayfurnaceman]

Welcome GFM

[@StagArmslower]

I have humidifier's transformer burning out in few months of running. The water valve solenoid draws 1.2 amps at 24 VA it's 29 watts. Transformer is 40 watts. The voltage to primary winding is connected (as installed by technician) to blower connector; one neutral and L1 (120 volts)so valves opens when blower operates. Any suggestions why this happens, maybe spike from blower's capacitor, any sugestions

[@grayfurnaceman]

I would guess that the solenoid is sometimes sticking. If it sticks, it sometimes will draw more amps and could exceed the rated amp draw of the transformer, thus burning out the transformer. GFM

[@Nichlo88]

You know what I have imo a really great service were I found a broken transformer. Let me share this with you gray. Service call for a heating system the homeowner said the system came on so loud it would vibrate scream etc... so badly that the neighbors could hear it. Went and look at the system had no power on the low voltage side. It was coming in but not relaying 120 to the 24 volt side turns out the transformer actually shook off the board! making it work intermittently it broke the sauder

[@toxicsneeze]

What if I DO have continuity on both the primary and secondary side but when I hook the thing up I still get no voltage on the secondary side? Clean 121v on the primary side... I've gone through ur whole series and I'm still at a loss. I'm on transformer #3... I have no continuity on on relay side (with transformer unhooked) in the open position (like it should be) and now I have 3 seemingly dead transformers so I can't test for amperage on my equipment side either.... I'm mostly just ranting... This is frustrating. Thanks for the help u did provide....

[@grayfurnaceman]

If I could ask a few questions. You are sure you have 120v in? Have you hooked it up with no wires on the secondary? If so, did you have 24 volts on the secondary? I am thinking you have a short in the circuit and the transformer either has a fuse that's blown or the secondary winding has an open. Merry Christmas GFM

[@J.RRandallIllinois]

our furnace a n.g Goodman has failed twice this winter. The furnace is 4 years old. I was getting funky voltages at the thermostat so I check the transformer and noticed what appeared to be a cut wire on the boot where it attaches to the secondary of the trans. , so I put a new boot crimp it and put it back on trans. and it worked for about 8 weeks and then happened again this time to the other side of the trans so I repeat and the furnace is currently working but in the back of my mind I'm concerned bcuz I didn't notice any heating of the wire and it was a nice clean shear so I don't think slight vibration would cause this but can I get some professional opinions out there, I'm curious, thanks.

[@wnorris1567]

My gas heater isn't working, my transformer is only reading just under 11 volts coming out. Does this mean my transformer is bad or is it likely something else? Thanks for the video

[@grayfurnaceman]

120 volts in, with no effective voltage coming out, bad transformer. When replacing the transformer, check output amp draw. If over 2 amps, you have a short in the control circuit and the new one will fail. GFM

[@Dear1970]

My mother in laws house had a power surge from broken exterior power line …..it fried a few household appliances …. Lennox elite Furnace has no power do you think it could be the transformer?? Circuit breaker is fine and has 110 at furnace

[@grayfurnaceman]

Check for 24 volts between R and C at the furnace terminal board. 24 volts, transformer ok, no 24, transformer failed. GFM

[@Dear1970]

@@grayfurnaceman that would be Red and white (common) wire on circuit board?what is GFM mean? Also will a low voltage non contact work because it is only good from 50 to 1000 volts so it won’t work on low voltage end of transformer?

[@Niempho]

Hey Gray, i asked a question awhile back about the only problem I couldn't figure out. I had 120v in the primary, but zero coming from the secondary. I figured it was the transformer and I replaced it. I put in a new transformer, but the same issue. I checked resistance and transformer was fine. It ended up being an eletrical issue elsehwere that caused it

[@Ziji-LetYourSoulShine]

Where was your electrical issue? When I test my transformer, when it is not connected, the meter reads resistance on the high side and the low side. Like 18 ohms on the high side and 1.6 ohms on the low side. The circuit board has no power when I connect the transformer. (No red light. Nothing works.) I've got 120 v at the lines that go into the circuit board. And 120 v coming out of the board through the wires that go to the high side of the transformer when I push the door switch, but no voltage coming out the low side of the transformer. I don't know if the transformer bad, even though there is resistance when the transformer is unplugged. I cannot figure out why there is no power to the board.

[@cafe80s]

@@Ziji-LetYourSoulShine Did you ever find the issue? I'm in a similar situation.

[@jimbarron8688]

You must have 120volts going to the black wire of the transformer primary winding and equally important is you have a good neutral attached to the white wire of the primary winding. Resistance between the black and white indicates the winding is intact. The secondary winding is much more robust and failure there is not common. A quick continuity check between the secondary terminals should show a resistance indicating it too is good. Alternatively you could attach a cheater cord to both primary wires black to black, white to white and plug it in. If you do not show 26ish volts A/C on the secondary the transformer is bad. Note: Be sure to check at the secondary terminals for 24 volts as some transformers are isolated from chassis ground.

[@LetsbeReal210]

I’ve learned so much from your videos! Thanks

[@grayfurnaceman]

Welcome GFM

[@surgingcircuits6955]

Connecting primary to 120VAC... No load on secondary... Aren't you creating a dead short? Or, is the magnetic field the load at this point? Thx.

[@rdoonanco]

what should the primary side have for resistance if it is working? I've tested my transformer and it has 2ohms resistance on the secondary side and 25.5ohms on the primary. Thanks

[@grayfurnaceman]

Those numbers sound about right. GFM

[@jimbossemi-customs3129]

Thanks for the video!

[@grayfurnaceman]

Welcome GFM

[@briancarroll6803]

It goes without saying, but I'm not a technician.. I do however manage to fix more things I try to work on than not, so while at my grandfather's house on Thanksgiving I thought I'd try to figure out why his heat works intermittently. Older model Tappan by the way. I was told a few good wacks on the side of the air handler usually gets it going. Obviously points to a dying relay of some sort - I do know that much. I found a relay but as I'm looking over and thinking through how this thing works I try turning it on with the fan "on" instead of in "auto". It works fine, instantly when you switch to "on" every time. It's a single relay, obviously it isn't bad - I think. As they say, if you reach for a bigger hammer and that doesn't work, your problem's electrical. Onward. I pulled the leads that are coming from the transformer I found and get about 26vac when the fan is set to "on" but only about half that when in "auto". This is where I dead end. The fact it's about half the voltage isn't lost on me but I can't work out why, or if that's just a red herring of sorts I should just ignore. 13 vac just isn't enough juice to energize the 24V switch is my conclusion I'm confident of. Any thoughts for further troubleshooting and potential home based repair? Note, he lives in the middle of nowhere, which is why I'm not just running up to the local hvac shop and picking up a new transformer before I head home. Thanks

[@briancarroll6803]

For future readers: I don't have an explanation, but I changed the thermostat and all is well.

[@mike198383]

So the Transformer is not showing any power at all on the 120. so i started to look at the capacitor so could that cause the main feed to not reach the transformer if it had failed?

[@grayfurnaceman]

The capacitor has nothing to do with power to the transformer. You have a high voltage problem. GFM

[@mike198383]

I started to think about that to so i started to look at the power going to a switch that is before the door safety switch and its only showing 7 volts so there is a big problem. After taking it apart the switch is quite old and so i will replace with a new one and clean up the connections and see if that solves the issue. Will respond if that does not work and after seeing that the 120 was not hitting the main board that is what proved your comment about cap and also the transformer.

[@grayfurnaceman]

If you are testing with the ohmmeter, the finger will not upset the readings. GFM

[@shanebrown5935]

Excellent video! Thanks for posting this! I have a question: what is the acceptable voltage range coming out of the transformer? I hear people in other videos talking about 27 volts. My thinking was as long as it is at or above 24v it should be ok. Can you chime in on it please?? Thanks!

[@grayfurnaceman]

26 to 29 is ok. Under load it may drop to 24 to 26. 22 or below is a problem. GFM

[@Jnewman161616]

What if we are getting 30Vac?

[@raycarr225]

Can't find anything on testing for mA AC. Specifically,a transformer with an output of 15v AC/500mA AC rating.

[@fluevano1204]

Hello my Ducane furnace operates normally except it has one problem I'm concerned about. When I plug it in I hear a faint electrical humming sound, the led light also stays on. Is this normal ? or would I have to change out the transformer?

[@grayfurnaceman]

Humming of the transformer is normal. GFM

[@bitsnbobs1969]

they also have fuses under that tape worth check be for scraping it

[@tommonti1830]

I have a York 025-28671-000 HVAC Transformer. Should the transformer be hot to the touch of the finger when I have all breakers turned on but the ac unit turned off?

[@joex110]

Also what does it mean if I plug in the common and hot line then both of them are reading 120v off the ground? I’m assuming that it means something inside the transformer made a bad connection

[@grayfurnaceman]

Your reading its normal. The common is connected to to the hot, so you will read power. GFM

[@ip5232]

Is it possible that the 24v would be intermittent? I mean T stat is on but as soon as it kicks either AC or heat it will go out (AC, fan, heater fan and t stat goes blank) but it 4:57 comes right back.

[@grayfurnaceman]

This one sounds like you have a short in the low voltage circuit. GFM

[@KAMNC]

MY dad has an old electric furnace and the blower motor stays on all the time. I unhooked the thermostat wire still runs. it doesnt have a circuit board that i see. the only thing i see is a transformer. What could keep it running all the time?

[@grayfurnaceman]

Nope. Electric furnace? GFM

[@WasimAkram-dv1ch]

how can we calculate the capacity of a transformer? Like 750 Watts or 1000 watts, i am asking this because i bought a transformer from a place for my Power inverter. now the issue is the shop i bought it from claims its a 1000Watts transformer but i checked it with two other person they say no its a 750 Watt transformer. Now how can i calculate and be sure?

[@loudspea]

liked the video .... you mentioned a followup video, so as not to keep blowing transformers.

[@hvacrickone]

I like your videos a lot,you get two thumbs up in my book young lad :)

[@Nichlo88]

Also Gray I had a question for you is their any way to test Transformers that are attached to a pcb board? my question is I was replacing aboard in a Monitor heating unit kind of like a rinnia space heater. I replaced the board left got a call back still didn't work. Felt the transformer in the newly installed board and it was super hot. Is their some way you can test electrical components on PCB boards etc... so you don't have to swap out to check if the board is bad?

[@geojor]

thank you for your expertise...

[@aymannurshazwan4944]

Hello, i want to ask. My secondary transformer continuity is 0. Is that mean my secondary transformer is broken?. And my transformer is step down( 240 to 24v), when I check the output voltage. The voltage that I get is 32V. Its normal?

[@grayfurnaceman]

Your 2 readings are incompatible. You cannot have an open secondary and still read a voltage on the secondary. Double check your readings. The 32 volts seems high. But it may be an open circuit voltage that would reduce to 24 to 26 under load. GFM

[@Synaux]

Great video! I am 99.9% sure my transformer is bad. I'm in s. Texas and was using an inverter to power the furnace during the storm. In the middle of the night the blower motor would power cycle at very low rpms. In the dark I accidentally shorted the switch receptacle (what i used to power it). Now if I put 110 direct to the motor it doesn't power cycle but VERY low rpms. Control board and thermostat is not connected. Am I looking at a transformer and a blower motor and maybe a control board?

[@grayfurnaceman]

If the furnace operates at all, the transformer is ok. Sounds like you may have damaged the control board and/or motor end bell. GFM

[@Synaux]

@@grayfurnaceman well not even the led indicator is turning on. To be more precise, if I supply 110 to the blower, even with the control board and thermostat disconnected, the motor should run at full speed or no? Right now it runs at ~100 rpm. Thanks for replying!

[@grayfurnaceman]

@@Synaux That depends on what motor you have. If it is a PSC motor, it should run full RPM. ECM probably won't run at all. GFM

[@Billstang]

I have a goodman 24 volt transformer I replaced. I disconnected the old one but on the new one on the output (secondary side) it doesn't tell me which tab connector is hot and which is common. The 120 side is clearly marked. Is there any way to figure this out? I'm afraid I'll reverse the polarity and cause a problem.

[@grayfurnaceman]

There is no reversed polarity on these transformers. They can be installed using either terminal as hot. GFM

[@surgingcircuits6955]

neb AC, not DC.

[@SnowyOwlPrepper]

OL is over limit on resistance scale. Infinite resistance air or open circuit. At least that was my experience when using a meter back in the 70s.

[@michaeldavidson9939]

My problem is high voltage. I have 247 volts coming in and am putting out 29.6 volts. I am having too rapid failure of sequencers as a result.

[@vajkaus]

What is the problem if I have 2 identical units and both transformer read 24 volts at the secondary on unit #1 but both read zero volt on unit #2. Both units has 120 volts going to the primary of the transformer. Any idea?

[@grayfurnaceman]

Are the units twinned twinned? GFM

[@vajkaus]

No, each unit are used for different section of the house. It is Bryant heat pump with backup auxiliary heat.

[@grayfurnaceman]

@@vajkaus You could have an internal fuse in the transformer. GFM

[@msj103105]

Hello, having a problem in cooling mode for a Heil AC, the inducer fan and blower fan are running at the same time but the condenser doesn’t not kick on. Thought it was the contactor but found this problem after. Any idea.. If I push the plunger in condenser fan and compressor comes on

[@grayfurnaceman]

You are not getting control power to the contactor. This could be a wiring problem between the indoor unit and the outdoor unit. You could also have low charge that has opened a low pressure switch. GFM

[@msj103105]

@@grayfurnaceman thanks Gary would that cause the inducer fan to run also at the same time??? Thanks again

[@grayfurnaceman]

@@msj103105 That one could be a failure in the control board or the furnace limit is open. GFM

[@msj103105]

@@grayfurnaceman found that the limit was open gonna replace thankz

[@GalaXy808]

Hey chief! I have a question if you touch with your finger while you checking?is it gonna give you a wrong reading ? That's why I can't do my testing.

[@petesingh292]

GrayfurnacemanI burned 2 transformers , and all the time it happens on primary side (120vac) when I found the short on low voltage side . I did all the research but nobody came with definate answere . Would you please explain the theory of transformer?

[@erickandrade1921]

Ive had the same thing happen too me. I was always taught a low voltage short shorts the secondary but i replaced a transformer on one of my dad's rental home units and I found the wire going to the pressure switch was rubbed and shotred on the copper suction lin but I looked in the back of the transformer and the primary was burnt. I didnt know why it burnt the primary

[@VIAGRA465]

does the Vo of the Transformer always read 24V in order to turn the unit on? what if it reads only 22v?

[@grayfurnaceman]

Open circuit voltage should be 26 to 28. When under load, I would expect 24 to 26. 22 seems low and you could have an excessive load on some component. GFM

[@glendooer6211]

Got one from China ..complete Dud . think they would test before???

[@grayfurnaceman]

Probably not. GFM

[@cintipw2759]

Could a transformer work intermittently or does it fail completely? Seems I'm getting intermittent power to thermostat. When I test transformer contacts (where thermostat wires are attached) I get no reading. I open the box the transformer is mounted on (so jiggling the transformer), reinstall and get power to thermostat - off and on, but (fingers crossed) on for now.

[@TriDaddy]

Cinti PW- plus 1... Gary, can you guide us?

[@grayfurnaceman]

If the question is can a transformer work intermittently, It could but it is very unlikely. By far the majority of transformer failures are not caused by the transformer. They are caused by shorts or chassis grounding in the wiring or components. GFM

[@TriDaddy]

grayfurnaceman You are right, 24v supply was good at the transformer. After further research my blower motor shuts off while the burners are still lit.. (intermittently-thermostat heat setting with auto fan). This happens until the overheat circuit cuts 24v to the "R" thermostat wire. Blower has good bearings, doesn't make noise on startup, runs when 117v are present and doesn't run when 117v isn't there. Note when 24v to "g" thermostat wire, fan runs. I've got past the overheating by keeping the fan to on instead of auto. Is there a way to check the relay on the circuit board lennox bcc3-1 LB-89859 ? I did not have the correct multimeter to check microfarads at the capacitor... I'll bring a tool home from work tomorrow. Anything else I should check?

[@grayfurnaceman]

It is possible the motor is overdrawing power. You can try replacing the capacitor. Probably no way to check the relay. GFM

[@Ziji-LetYourSoulShine]

When I test my transformer, when it is not connected, the meter reads resistance on the high side and the low side. Like 18 ohms on the high side and 1.6 ohms on the low side. The circuit board has no power when I connect the transformer. I've got 120 v at the lines that go into the circuit board. And 120 v coming out of the board through the wires that go to the high side of the transformer when I push the door switch, but no voltage coming out the low side of the transformer. (And no red light on the board. Nothing works) So is the transformer bad, even though there is resistance (continuity) when the transformer is not connected?

[@grayfurnaceman]

First, throw away the ohms readings. Check voltage into the transformer, then voltage out. (I know you have done that). You have your answer as it relates to the transformer. GFM

[@Ziji-LetYourSoulShine]

Thank you!

[@erikthorsen4466]

I am dealing with a Carrier RTU that had a bad inducer motor. Turned disconnect off several times in the process of replacing motor. WiFi t-stat of course loses connection when disconnect is turned off but comes back on within a minute or so after re-energizing disconnect. 3rd time turning disconnect off and then back on however and WiFi signal never did reconnect. Modem is fine and working for other units just not connecting on this one. I checked transformer primary and secondary voltages and while primary is good to go, my secondary is reading 22 volts under no load. This is a 208/230 system running at 208 volts. Have not been able to get back to it today due to constant rain. This transformer btw, has a built in circuit breaker protection and it is not tripped. I am wondering if turning disconnect off and back on several times had something to do with transformer now only putting out 22 volts with no load even on it and also loss of wifi stat connection to unit.

[@grayfurnaceman]

I don't think the disconnecting had anything to do with the problem. I would be looking at the transformer wiring. It could be wired for 240 volts. That would account for the low voltage. GFM

[@erikthorsen4466]

@@grayfurnaceman It's been running with that transformer and didn't stop until I had turned disconnect off and back on several times. Now, no connection to wifi stat and only 22 volts out of transformer under no load. I suppose you could well be correct but this unit has run for 2-3 years with that transformer in it and hasn't had the wiring changed. Usually on a miswire of the multi tap I see them either not work right from the get go or very early on it becomes an issue. I suppose it could have lasted this long before becoming an issue but I don't think I've ever experienced that.

[@grayfurnaceman]

@@erikthorsen4466 I have had both experiences. I would check the wiring. GFM

[@erikthorsen4466]

@@grayfurnaceman You were correct sir. Whoever installed the multi-tap transformer wired it for 240 instead of 208. I have been the one they have called for service since 2017 so it was installed prior to us getting the service contract. Very unusual to have not had any issues for the past 2 years until now but there you have it. Appreciate you pointing me back in the right direction. I should have checked that earlier on.

[@grayfurnaceman]

@@erikthorsen4466 Glad you got it going. GFM

[@theladydaisysf]

Can a faulty transformer cause humming and vibrating in the house?

[@grayfurnaceman]

+Daisy Jones Yes. Replacement is the only option. GFM

[@garrygemmell5676]

So can the wifes vibrator so best to check! >;o)

[@jheromeberon2264]

I have a 24v transformer but the output was only 20v,,it was the reason why transformer tripping off

[@StingrayLS7]

To check my 24 volt out put what do i set my meter on volts or AC volts thanks

[@grayfurnaceman]

AC volts. GFM

[@franka6258]

hello, love your videos, you've taught me alot which I've applied in the field.. can you make a video about ghost voltage? how and why does ghost voltage occur. appreciate you alot. thanks very much!!

[@grayfurnaceman]

Frank A I will put it on the list. GFM

[@ducklandwikeno]

Wires from the low voltage touching together would short the transformer out . Thats most cases right . But I bet there are others too ,like it just getting old . One thing I found out is if they get real hot , something is wrong from the start .

[@grayfurnaceman]

Thanks for the "young lad"

[@billsherenow]

That piece in the beginning of the video that was what we were looking for. Looked like a voltage converter and not a transformer.

[@jayt2257]

what’s the difference?

[@joshuatruax3726]

So when you checked the two wires going to the transformer when it was shut off that was suppose to be 120?

[@grayfurnaceman]

+Joshua Truax The incoming power should be 120 volts GFM

[@joshuatruax3726]

+grayfurnaceman Oh ok thank you.

[@EurekaRecycler]

Is the 24 volt output end polarized?

[@grayfurnaceman]

+EurekaRecycler In most cases, no. GFM

[@EurekaRecycler]

So most commonly the transformer get toasted because a short somewhere else? Thanks

[@grayfurnaceman]

+EurekaRecycler That's correct. Transformers are extremely dependable. GFM

[@hwesson75]

TLDR: If you notice electrical items dangling from the rafters in your attic that do nothing, go ahead and disconnect them asap because they could possibly do bad things. And it seems I'm also building things with dud parts. D'oh. We had one of those transformers pretty much exactly like that one wired up in the attic for a doorbell that had been removed in probably the mid to late 70's... At some point in the last decade, the old low voltage doorbell wiring that was strung all over the place shorted, and apparently the transformer got so hot it melted the primary into a dead short, which then melted almost the entire length of its dedicated 14 gauge wire to the breaker box before it finally went open. How the house didn't burn, I have /no/ clue. Meanwhile, I'm working on a homebrew thermostat setup (12ga power cord, thermostat module, 24v/40va transformer, 40A contactor for overkill, 20A outlet, all squeezed into a project box) to use on a window a/c, space heater, turn a deep freeze into a fridge, etc. It works great, but the practically brand new transformer gets hot enough with no load that I can't hold my fingers to it for more than a few seconds, and it shows 20 ohms on the primary... Pretty sure I'm going to need to get another transformer, wouldn't you think? :p

[@hwesson75]

Found another video with someone ohming out this exact model transformer, and it read practically identical to what I get with mine. v=M5y2FC0SYXA?t=277 Pretty sure still that it's not supposed to get hot enough to smell frying plastic when it's plugged in with nothing connected to it, though.

[@grayfurnaceman]

@@hwesson75 That transformer should not have any heat buildup if the low voltage circuit is open. Are you sure there is no load? GFM

[@hwesson75]

​@@grayfurnaceman Yeah, I have it sitting on a desk with nothing connected but white/black clipped to test leads stuck in a power strip and it still gets hot. It's slow to get there, wouldn't notice in a short test, but at about 30 minutes it's pretty warm, an hour it's up to around what I'd think normal if it had been actively holding a contactor, and after a few hours you wouldn't really want to pick it up bare handed for more than a second or two. And I just now noticed, after it sitting there plugged in for about an hour and a half so far this time, that its hum has ramped up from nearly non-existent cold to the point where I can hear it making the desk hum and can feel the vibration when I touch the thing... This has me starting to think it's probably a manufacturing defect. Likely either a poor winding job, or bad lamination between some of the plates, would be my uneducated guess. Whatever it is, I think I'm going to be safe and just get myself something completely different to replace it with. Although, for something that only draws around 4 watts, it does make for a rather effective (but oh so very sketchy) hand warmer on a cold night. lol

[@grayfurnaceman]

@@hwesson75 I would have to say it is toast. GFM

[@hwesson75]

@@grayfurnaceman Well, I got another one of the same type, but a different brand... This new one still gets uncomfortably hot after a few hours of 120v sitting on the desk, but unlike the other it's /just/ at the point that I can hold on to it for a while. Looks like I am going to be ventilating that project box after all, because things are only going to get hotter while holding the .13 amp load for possibly several hours at a time. Ugh... There's going to be plastic shavings /everywhere/. Darn stuff is nearly as pervasive as glitter is. lol

[@khosfarzaneh7690]

I accidentally found out that the ground wire in one of the switches that was causing GFI tripped is hot. What is the cause of it?

[@grayfurnaceman]

Khos Farzaneh It probably does not have continuity to the ground in the panel. Look for wire nuts that do not have all the ground wires inside. Once you have found the open circuit, the breaker may trip. If so, disconnect appliances until you have found the culprit. Be careful here, high voltage. Hope this helps. GFM

[@grayfurnaceman]

Cool story! GFM

[@vankeymishra9047]

Plz full connection transfer

[@MoosePhorus]

Can a transformer go bad as in trying to output more power than it suppsoe to? The Fuse on my circuit keeps blowing. Somtimes it will turn on but if i unplug it and plug it back in the fuse blows instantly. Nothing on my ciruit board looks shorted, so i'm pretty sure its the transformer. From what i know is the transformer intakes ac and converts it to dc. It has three wires on the dc side and i have no idea how to test it. I just cant firgure out why somtimes it works but then goes out after i unplug it and plug it back in. Please help

[@grayfurnaceman]

The transformer almost never would do that. The transformer converts 120 volt AC to 24 volt AC. You have a low voltage short. I did a series of videos on troubleshooting low voltage shorts. GFM

[@markmomper9609]

thanks for this video - it's pretty funny, but i couldn't figure out what i did wrong because the furnace wouldn't fire up...didn't have the door closed so it wasn't powering up (doh)

[@kdgrayson9944]

Don't feel bad about that, it's extremely common! Many service calls come after an air filter replacement and it is that door switch not quite being closed or opening.

[@1242chisox]

Yes extremely common.

[@electricboogie709]

GFM, is there anyway to ask some questions. I am perplexed with a couple of issues at work.

[@grayfurnaceman]

J Hartranett You can use this comment forum or better, go to grayfurnaceman website. There is a comment forum on the home page. GFM

[@electricboogie709]

grayfurnaceman thanks gfm. I am really stressing out over it. couldn't sleep. Some things are obvious. Some seem like that arent.

[@rocker8692]

Good video slurp slurp

[@sammarchetti2484]

The problem is that someone let the smoke out of that transformer

[@biblebloopers946]

Why do you only get 12 volts when reading your 24 volts to ground?

[@bobbyatman273]

Putting wires "here" testing "there" ifc...

[@RineboBohead]

It’s toast🔥🍞

[@Shane23Armada]

I bet its one of those fkin hampton bay transformer

[@dawsondau8121]

Not clear

[@vankeymishra9047]

give 120 and coming 24v

[@GalaXy808]

(: thanks

[@lakotapride7370]

Fake news