Experts Give Verdict on the Cable Overload Row

[@_Miner]

How does a CT play any part on their bills though? a smart meter (or regular meter) has its own metering and does not rely on anything external to the meter. Even with FIT there is a seperate meter for this calculation. Did I miss something or is there some kind of metering with a CT (which could be abused very easily)?

[@yngndrw.]

With the note about solar installations, I can only assume it's the CT used on a hybrid solar inverter. With the CT installed backwards, the inverter will attempt to charge the battery any time you import any electricity as it thinks that it is exported. This will then increase your import and the inverter will increase its charge rate up to the maximum rate. I'd expect it to then continue charging at the maximum rate until it's full - You'd end up with some very strange behaviours. All assumptions, of course.

[@_Miner]

@@yngndrw. But that would only increase usage for importing energy up till the battery was charged fully. eventually no more could be imported for that, even if it was consumed that would then mean no imported energy till the next charge. Even that would not account for a £3k bill. Something doesnt add up here.

[@yngndrw.]

@@_Miner It will be able to flip direction when the battery is fully charged, in that case as soon as you start exporting from the solar panels the inverter will also start to export - Until the battery is fully depleted. It will essentially form a latch, flip-flopping between fully charged and fully discharged. With the difference between import and export rates, I could imagine it quickly racking up that sort of bill. Additionally, depending on the setup of the inverter, it could be set to have upper and lower charge limits which would make it very unpredictable.

[@G6EJD]

The billing CT was attached to the wrong cable.

[@edc1569]

@@yngndrw.haha it would be working against you the whole time, quite funny really. Hope whoever installed it is compensating the homeowner

[@roberthuntley1090]

{2:15} EOn refitted the CT Clamp to my meter tails the wrong way round when I had my smart meter fitted in 2021. It was easy enough to spot, just look for the disproportionate rise in electricity demand on the instantaneous smart meter display when turning on an big electrical load (e.g. turning on a 3 kW kettle led to a 6 kW increase in demand from the grid). The cause of the problem was that the solar PV diverter (controlled by the clamp) increased the power supplied to the immersion heater instead of reducing it when the household demand rose. At least the energy wasn't wasted, it just ended up in the hot water system.

[@emiletetrt]

(prematurely) EXFOLIATE and EGREGIOUS I'd wager. Also, ChumpFix looks pretty neat having seen some very interesting mounting options by DIYers. As for the cable overloads I can't comment on the British regs, but in Denmark as long as the equipment, which is permanently mounted, doesn't overload the cable the fuse can be whatever size that still ensures short circuit protection for the entire length of the given cable.

[@efixx]

V. similar to UK regs to be fair. 😊

[@ericmarkpalmer9043]

Looked at the plaster board fitting, has the rules changed? 559.6.1.5 tells us it must take a load of 5 kg, can plaster board really take that load?

[@JimWhitaker]

So what 433.3.1 is emphasising is the need to differentiate between "overload" and "fault" conditions.

[@geraldelwood9660]

Re undersized cables for overload protection : Does this mean that only TT supplies can take advantage of this loophole - as TN supplies use the MCB (even if in an RCBO) for Fault protection and the RCD is only supposed to be for Additional potection. Whereas in TT supplies an RCD is required for Fault protection and would therefore provide ADS under fault conditions before the cable was compromised ?

[@philipeardley4462]

The same problem with the solar install from Octopus with the solar install clam in the wrong place and upside down affecting battery charging and consumption/export

[@james123j1]

A smart meter doesnt rely on a ct clamp so how can it cause this issue?

[@retrozmachine1189]

Depends on the meter. Most do have the ct inside the meter but you can get them with an external ct. I think your individual suppliers over there provide the metering rather than the network so it's potentially an issue. This is all theoretical as I have no practical knowledge of what happens over there.

[@bas5946]

@@retrozmachine1189 There are no external CT clamps used on billing energy meters in the UK, this would make it super easy for customers to unclip it during high demand and have a zero bill.

[@johnlloyd3377]

I recently had a PV system with battery storage installed along with a car battery charging system. Both systems have their own separate Apps which provide energy consumption/generation data. After a few days of crazy data readings I suspected that the problem was the CTs and having investigated I found that both CTs were installed on the wrong cables. This had nothing to do with the meter but both Apps were indicating wildly incorrect data.

[@edc1569]

Fun isn’t it paying for professionals and then you end up having to fix it.

[@IvyMike.]

I always make sure I over size the cables I install, even if it's just a few mm2, for piece of mind that the cable/install is never going to be the problem.

[@edc1569]

A few mm on 1mm lighting circuit is what? What’s the point in oversizing, no one wants to deal with oversized conductors. Grid switches are hell enough with 2.5mm

[@Mark1024MAK]

Why over size? And especially with lighting circuits, with most domestic lights now being LED how are your ever going to overload a 1mm sq cable if installed to the regulations? Similarly, for other typical domestic circuits in the U.K.

[@darylsavage119]

If in industry yea sure, go for a 35mm swa when you need 25mm In a house 1mm is fine

[@CBE-d6j]

Energy savings for one. It’s in the regs for environmental considerations when designing circuits. Bigger cable less resistance - saves money. Long gone are the days of saving money on increased conductor sizes. Obviously still adhering to being able to safely terminate cables.

[@markrainford1219]

Standard cable sizes are already oversized.

[@HeathenGeek]

1:50 err. . . what's the reg that says the minimum csa that can be used to supply power must be 1.5mmsq?

[@edc1569]

None

[@Mark1024MAK]

If the minimum cable size to supply power is 1.5 mm sq explain lighting circuits that use 1 mm sq cable and which are normally protected by a 5A fuse or 6A MCB? Is a 500W quartz halogen lamp not using any power?

[@markrainford1219]

@@Mark1024MAK He said power, not lighting. Think he's referring to 1.5 being allowed on a unfused spur from a ring?

[@thattoolguy9432]

Have used the canalis system on a lot of big shop fits, brilliant kit . That thief isnt quite Miss Money Penny, more like Miss Fishy Fanny... Happy new year Joe

[@TheYohtube]

I have always wired a 1.5mm oven flex together with the (supplied) induction hob cable into a dual cooker outlet supplied by a 6mm cable on a 32 amp mcb for example.

[@edc1569]

Most induction jobs can pull 32A by themselves, you must have to derate them? Not how I would want it wired anyway.

[@TheYohtube]

Diversity takes effect here, yes even with induction as they pulse on and off in sync with each hot plate. John Ward has done a video stating wiring 1kw ovens into a cooker outlet is OK. They can not overload, and fault conditions are catered for by appropriate sizing of cpc.

[@bas5946]

Something doesn't add up with the External CT clamp malarkey, They're not used on domestic smart meters as a means of measuring energy in and out of a property that I am aware of, or the customer could just unclip it resulting in zero energy bills, so that leaves the CT clamp from the Solar PV system most likely with a battery storage add-on, when a current transformer is reversed on a Hybrid Solar PV system, the inverter thinks its exporting to grid despite energy being drawn from the grid so will charge the battery storage up, once the battery is at 100% it will sit there at 100% as it never detects a hose load from grid. How would this result in a £3000 bill in a month unless they have an absolute monster of an ESS system. There is more to this story than suggested in this video.

[@chrissharpe2106]

Was chatting to wholesaler about how crap solar lights are and was given a Luceco solar light as a “demonstrator” and have to say it’s fantastic, light enough to be put up with some double sided tape and it lights up the front door a dream.

[@retrozmachine1189]

Stealing a light fitting? Sounds a bit fishy to me.

[@efixx]

😂💪

[@JamesMills-w1j]

@@retrozmachine1189 Looks as though she'd wrapped what she thought to be catch of the day.. 😜🐟🐠🐟

[@G6EJD]

CT’s don’t measure power usage in Amps, they measure Amps that can then be used to calculate energy usage.

[@davefrizelle3882]

'Exfoliate' and 'maestro' would be my guess for this week's words. Cheers :)

[@efixx]

Great guesses Dave, hope you're keeping well! 😃

[@davefrizelle3882]

@@efixx I am indeed, and enjoying all your content. I hope you all are keeping well too. I see a live stream scheduled for Wednesday ... looking forward to that!

[@johnlesoudeur3653]

The fish and chip shop was focussed on net zero.

[@efixx]

Excellent work! 👏👏👏👏

[@grumpyhale821]

14000 steps a day? Im on 14653, I average 15k to 18k steps a day, sometimes topping 20k with 22676 on 14/12/24 and 23901 on 6/12/23 as the highest I've found.

[@adrianupnorth]

Chumpfix is going to be stocked on the van. Thanks Joe

[@efixx]

Nice one Adrian. 💪

[@LeighWinspear]

All meters surely need calibrating every year at least!

[@timballam3675]

A current clamp SHOULD have no effect on an electricity meter. If it does then questions need to be asked of how the meter passed CE and CPA qualifications....

[@mark_just_mark]

Exfoliate and Kicker 😁 I hope I win this week ‘let Minnow’ - I will ‘Tuna’ in next week!!! 😜

[@michaeljohnson1006]

That's ok as long as someone doesn't come along after and put a 13amp fuse in the circuit.

[@Mark1024MAK]

Assuming you are talking about the example given in the video, how does changing the fuse to a higher value increase the current and power demand of a fixed appliance? Only if the appliance develops a short circuit fault will the current increase and then even a higher value fuse such as a 13A should blow. There is a difference between short circuit protection and overload (over current) protection.

[@andysims4906]

A working smart meter . Even if its wrong Well what ever next

[@TheChipmunk2008]

Octopus shouldn't be relying on CTs for billing purposes unless they're wired by a suitably qualified person and of an appropriate type, certainly NOT the stupid clip on ones

[@JasperJanssen]

The problem was that octopus put the CT back wrong after removing it during the fitting of the meter. They caused the installation to behave badly. Not wrong metering per se.

[@MegaFatboy92]

Yeh,….what he said

[@MarcusNailor]

Exfoliate & maestro 🎼

[@davideyres955]

Why the hell is a “smart meter” using a CT clamp to measure the consumption? They are not that accurate. And why the f. Are we paying £££ for smart meters that are hundreds of pounds that are no more accurate than a cheap device that can give you watts consumed that are a hell of a lot cheaper. And before anyone says smart meters are free they are not. The suppliers have been aloud to charge us more money on our bill to roll these “smart meters” for “free”

[@deang5622]

A CT does not have accuracy. It is neither accurate or inaccurate. Accuracy is a function of what is measuring the current provided by the CT.

[@deang5622]

A kWh meter doesn't require a CT to measure current. Evidently a more complicated setup is present, possibly using solar panels and feeding power back into the grid.

[@retrozmachine1189]

Actually smart meters typically do use a CT to measure the current, it's just internal to the meter. I can't think of a meter that uses a shunt to do it, but they are no doubt out there. As for accuracy the authorties consider a CT to be perfectly acceptable for measuring high amp services so think about that for a moment. Old spinning disc meters employ a current coil but its magnetic field acts on the disc rather than inducing current in a secondary winding. Before the local expert steps in, yes, there is a voltage coil in the spinning disc meter.

[@intercity125]

@@deang5622 They certainly do when you step above normal residential units...

[@Mark1024MAK]

Yes, everyone is paying for smart meters as part of their electricity bill and IMHO we are not getting value for money.

[@JohnDyerTheBrewer]

Exfoliate and allowance are my bet

[@Brian77766]

Exfoliate and Kicker

[@efixx]

Great guesses Brian, tune in next week to see if you got it right! 😃

[@MostlyMull]

Exfoliate and egregious?

[@hashtagger8694]

Prematurely and egregious

[@TheManLab7]

I wonder if that woman is native to the UK?

[@Chris-hy6jy]

Overlord current vs fault current? Two phrases for the same thing?

[@davidstone1579]

No, try again!

[@Chris-hy6jy]

@davidstone1579 an overload is certainly a fault from the point of view of the cable as it will likely overheat and even catch fire, in the same way it might if a fault occurs and it draws excessive current.

[@andyscott5978]

Fault is chopping through the cable with a spade. Dead short instantaneous current rise to the point where the Circuit Protective Device (MCB, fuse etc) clears (blows, trips etc) the fault. The cable should be able to pass the current from that situation without catching fire until the fault is cleared. Overload is when a circuit becomes overloaded. Meaning the load placed on the circuit is too big. Too big for what? Either the cable or the Circuit Protective Device. It’s much more than a one sentence explanation which is why electricians have to learn about this sort of thing. The regs aren’t well understood or well read. People see a headline and blindly apply it to everything even though there might be an exception to the rule. If you’re really stuck, then the section on basic definitions in The Regs should help a bit.

[@Chris-hy6jy]

@@andyscott5978 I think you rely on the regs too much. Let's say a cable gets damaged and starts arcing. Not a dead short but draws excessive current for a prolonged period. Let's say water gets into a junction box and causes excessive current to be drawn over a prolonged period. More current than the cable is rated for. I'd call those situations faults. I guess you'd argue they're overloads. Hence my point, they're basically the same thing. A fault should not just be considered a dead short.

[@Monkeh616]

An overload is where an intentionally connected load draws more current than the circuit it is connected to is intended to supply. A fault is where a damaged or faulty load or cable does this. The latter is almost invariably a far higher fault current than the rating of the protective device. If you don't believe me, try and arrange a low fault current via mechanical damage or water ingress, and have it be sustained. Then explain how your final example could actually occur in a real world situation, and get some assistance in calculating the odds of it. Probably find you're more likely on any given 10 minute walk to the corner shop to get hit by a crashing hot air balloon.. Or, to be a little less hyperbolic, a car.

[@Mircea007]

exfoliate and floundering

[@scubavids]

Exfoliate / egregious

[@Jasonf-km5mq]

Exfoliate, back-burner

[@TheChipmunk2008]

People saying stupid things like 'you can never do this' is because they don't read the regs

[@johnbryan1072]

prematurely exfoliate

[@jmw5233]

exfoliate + egregious

[@MKHNitro]

Exfoliate and egregious

[@efixx]

Nice guesses, tune in next week to see if you got it. 💪

[@Jasonf-km5mq]

Exfoliate, egregious

[@keiththesparky]

Stealing from a chip shop should not be made LIGHT of 😬 she was clearly a woman who was not worth her salt 🧂 (or vinegar) 😜 I’ll get me coat then 🙈

[@davemyers77]

Exfoliate Piscine

[@trevormorris1281]

Stick to the regs a good time served sparky knows when installing if things are done correctly floor area load if borderlining do calculations!. Be smart be safe don,t be in court for manslaughter through ignorance.

[@jeremycanning8934]

LOL, experts

[@deang5622]

Given they all have degrees in electrical engineering and you don't. I would call them experts and I certainly would not apply that term to poorly qualified electrical technicians.

[@professorg8383]

When I hear stories like the first one, I wonder how it is that the UK has not burnt to the ground!

[@snail_cactus]

quality fish puns there, 10/10 no notes

[@martinsimpson92]

Exfoliate and egregious?

[@sjbmann]

Exfoliate, egregious

[@DMosley7671]

Exfoliate and egregious

[@daleflaherty]

Exfoliate and egregious