New Plug In Induction Hob Tripping Electrics Occasionally

[adzyp]

Do you really think that clamping round N&L will show EARTH leakage?

Yes...?

 

[ericmark]

1) An induction hob is an electronic device and may need other than a type AC RCD although mine seems to have no problem with a type AC RCBO.
2) You have a lot of circuits through the RCD, so it could well be a build up of leakage from many circuits.

However the most likely is an earth - neutral fault likely nothing to do with the induction hob, but as the hob draws high amps the voltage difference between earth and neutral increases, so also any leakage earth to neutral also increases, and this is causing the imbalance between line and neutral and causing the RCD to trip.

Earth to neutral leakage is normally found using a insulation tester these are also often built into PAT testers, but can't be found using a multi meter most of the time, a clamp on ammeter may help, but either way hard for the non electrician to find the fault. I have all RCBO's which is a RCD and MCB combined so if some thing goes wrong, I don't loose as much, and earth - neutral faults are less likely to cause tripping.

So for you first thing is to unplug anything not in use, a bit of damp bread stuck in a toaster can cause the RCD to trip when kettle is used, if the toaster is left plugged in, as the switch on the toaster only switches the line, it does not switch neutral, so to switch neutral only way is to unplug.

For me it is easy, I have the testers and knowledge how to use them, but for you only thing I can suggest is unplug all items when not in use. Items which are double insulated are less likely to be a problem, one often they are double pole switched, and two no earth to leak to, but I really have never considered how to test for earth - neutral leakage without my meters, as never needed to do it.

 

[adzyp]

1) An induction hob is an electronic device and may need other than a type AC RCD although mine seems to have no problem with a type AC RCBO.
2) You have a lot of circuits through the RCD, so it could well be a build up of leakage from many circuits.

However the most likely is an earth - neutral fault likely nothing to do with the induction hob, but as the hob draws high amps the voltage difference between earth and neutral increases, so also any leakage earth to neutral also increases, and this is causing the imbalance between line and neutral and causing the RCD to trip.

Earth to neutral leakage is normally found using a insulation tester View attachment 321265these are also often built into PAT testers, but can't be found using a multi meter most of the time, a clamp on ammeter View attachment 321266 may help, but either way hard for the non electrician to find the fault. I have all RCBO's which is a RCD and MCB combined so if some thing goes wrong, I don't loose as much, and earth - neutral faults are less likely to cause tripping.

So for you first thing is to unplug anything not in use, a bit of damp bread stuck in a toaster can cause the RCD to trip when kettle is used, if the toaster is left plugged in, as the switch on the toaster only switches the line, it does not switch neutral, so to switch neutral only way is to unplug.

For me it is easy, I have the testers and knowledge how to use them, but for you only thing I can suggest is unplug all items when not in use. Items which are double insulated are less likely to be a problem, one often they are double pole switched, and two no earth to leak to, but I really have never considered how to test for earth - neutral leakage without my meters, as never needed to do it.

Thank you, appreciate that!

 

[ericmark]

Do you really think that clamping round N&L will show EARTH leakage?

Yes my house shows around 26 mA total, but that is shared between 14 RCBO's so no problem. However of the two clamp on meters shown, the yellow one only shows down to 10 mA increments so really not suitable for finding earth leakage, the red one do measure down to 1 mA increments, and is OK with AC, but on the DC scale testing for the 6 mA DC leakage not really much good as needs zeroing then not moved, and can't really do that over meter tails, so still a bit hit and miss with DC.

But the problem is most DIY people don't have either a clamp on or a insulation tester, even the cheapest are £35 each, and if bought then they still need to learn how to use them. I have needed to use PMR 466 two way radios to get a helper to turn items on/off in the past while watching the meter in the past, so easier with plug in stuff to use the insulation tester. I can do that on my own.

Again as electricians we know mineral insulated stuff is most likely the cause, so heating elements, kettle, immersion heater, washing machine, frost free freezer etc. The latter is a problem as only when in the defrost cycle, so testing neutral to earth is only way, and hope not double pole switched.

To in essence to PAT test all equipment in the home would cost too much, so if the home owner can say it only trips out when both induction hob and dish washer is plugged in, then it means less items need testing, the same if using all RCBO's it reduces how many things need testing.

 

[adzyp]

1) An induction hob is an electronic device and may need other than a type AC RCD although mine seems to have no problem with a type AC RCBO.
2) You have a lot of circuits through the RCD, so it could well be a build up of leakage from many circuits.

However the most likely is an earth - neutral fault likely nothing to do with the induction hob, but as the hob draws high amps the voltage difference between earth and neutral increases, so also any leakage earth to neutral also increases, and this is causing the imbalance between line and neutral and causing the RCD to trip.

Earth to neutral leakage is normally found using a insulation tester View attachment 321265these are also often built into PAT testers, but can't be found using a multi meter most of the time, a clamp on ammeter View attachment 321266 may help, but either way hard for the non electrician to find the fault. I have all RCBO's which is a RCD and MCB combined so if some thing goes wrong, I don't loose as much, and earth - neutral faults are less likely to cause tripping.

So for you first thing is to unplug anything not in use, a bit of damp bread stuck in a toaster can cause the RCD to trip when kettle is used, if the toaster is left plugged in, as the switch on the toaster only switches the line, it does not switch neutral, so to switch neutral only way is to unplug.

For me it is easy, I have the testers and knowledge how to use them, but for you only thing I can suggest is unplug all items when not in use. Items which are double insulated are less likely to be a problem, one often they are double pole switched, and two no earth to leak to, but I really have never considered how to test for earth - neutral leakage without my meters, as never needed to do it.

Just out of interest, are RCBO's a straight swap for the ones I currently have in the existing CU?For example if I was to just swap out the Cooker circuit for an RCBO or one of the other circuits or are they a different physical size?

 

[ericmark]

I don't know that make of CU, a CU is a type tester distribution unit, and to retain the type testing only items sanctioned by the manufacturer can be fitted, or it stops being a CU. Also today most are metal and also have surge protection, maybe some one else will know if there are RCBO's for that box.

It would need the RCD removing for that way, which would likely mean new buss bars, or all the MCB's replacing with RCBO's and the RCD swapped for an isolator.

It does seem likely these will fit but I am not sure.

 

[adzyp]

I don't know that make of CU, a CU is a type tester distribution unit, and to retain the type testing only items sanctioned by the manufacturer can be fitted, or it stops being a CU. Also today most are metal and also have surge protection, maybe some one else will know if there are RCBO's for that box.

It would need the RCD removing for that way, which would likely mean new buss bars, or all the MCB's replacing with RCBO's and the RCD swapped for an isolator.

It does seem likely these will fit but I am not sure.

Ok thanks for your help.

Hopefully unplugging things will do the trick anyway. I unplugged what I could last night and turned harder to reach things off at the socket (does it make a difference?) and its turned on fine since so we'll see as i say, its always been hit or miss.

Since unplugging things though, I have noticed a couple of times that when turning the hob on the kitchen spotlights very very faintly dim quickly (almost unnoticeable) which I never noticed before. Could it be that im now on a thin line to the acceptable side of current?

 

[ericmark]

Some socket switches are single pole, others are twin pole, and there is little you can do to work out which are which, back in 2008 the regulations said "Every installation shall be divided into circuits, as necessary, to:
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced
by equipment in normal operation" there were other reasons as well, but those two raised the question as to if having a single RCD coving many circuits was compliant. However we saw the birth of the twin RCD CU and it has been used with very little reserve. AC always has some leakage due to capacitive and inductive leaking, and the insulation testers use DC so can't show that leakage, so until the system is energised it is near impossible to know what the back ground leakage will be, so before converting to RCD protection one could use a clamp on meter and measure, but even today the clamp on meters used my many electricians will not measure in 1 mA increments. So electricians are fitting RCD's with no idea how close to the wind they are sailing.

But although the price has dropped now, the RCBO to replace the MCB and RCD was expensive. Back in 2008 we were looking at double the price today, and also the early units were a lot longer than the MCB and would not fit in many consumer units, I can't remember when we started to see type AC and type A, I know when my son lived in a narrow boat looking at fitting type A due to having an inverter, so were around in 2008, but few electricians considered there was any problem using a RCD which was type AC and with a rating well below the DNO fuse size, supplying MCB's where the total was also well above the RCD rating.

This was to some extent also down to the DNO, 60 amp fuses on whole supply were common, the old Wylex fuse box used for years was only rated 60 amp, but a consumer unit should be rated 100 amp, but it seemed often when fuse size was increased little attention was paid to the equipment it supplied.

Subsequent editions of BS 7671 have it seems clarified the position, but one can hardly expect an electrician to return to all the homes he has fitted consumer units in, and upgrade them free of charge because it is now been clarified what he was doing was wrong, or can we, it seems this does happen with cars, and we do get recalls.

The problem is until things go wrong, we do nothing, I am guilty, I knew I really needed a hand rail on the steps down to my flat, but until I fell did nothing, after the event I paid out £500 for a hand rail, but a bit late then. Easy to say I knew I needed one, the steps did get slippy in the rain, but I was holding out and had intended to DIY the job, but at 72 not as quick doing the jobs to when I was young.

It is easy for me to say BS 7671 says this, that or the other, but you are the one paying, and easy for me to say fit RCBO's but as to if you could do the job, not a clue, I have no idea of your skill, and I know many electricians would not want to alter the existing consumer unit, we use to laugh at the sucking through teeth and saying jobs worth, but it has become literally that has become the case, if the schemes refuse an electrician membership that is his job gone, he today simply has to do as he is told by the schemes, he can't use common sense.

All in all the rules have not made it safer but more costly, can't even get a window fitted today without some legal bit of paper to say it is OK.

Hence the advice to unplug items not in use.

 

[adzyp]

Think I may have found a potential culprit or two here.

So I turned a few bits off the other night and I also turned off the integrated washing machine and dishwasher which I was meant to turn back on but forgot! (Socket is inside a cupboard so a pain to turn on/off every time)

Anyway, the hob seemed to work fine all day and night yesterday whilst they were still off.

We then realised they were both still off so turned them back on, thinking nothing of it.

Just pressed the power button on the hob as I walked past this morning and RCD tripped again, so im thinking its one of those.

What shall I check if I do a deeper dive on them 2 appliances?

 

[EFLImpudence]

What shall I check if I do a deeper dive on them 2 appappliances

Have we not answered that already?

I have not reread all the thread; perhaps you should.

 

[ericmark]

There seems to be two options, get some one in, or DIY, and not sure which is best or cheapest?

A insulation tester cheapest I could find cost me £35, and you need one to test further. Easy enough to use, clip one lead to earth pin on plug and other to neutral pin, set to 250 volt and press button. One is looking for a reading over 1000000 ohms or one meg ohm.

But if you get some one in, maybe not only find the fault but can cure the fault.

Likely the problem is the mineral insulated heating element in an appliance. But really need to test, not change to see if that works.

 

[adzyp]

There seems to be two options, get some one in, or DIY, and not sure which is best or cheapest?

A insulation tester cheapest I could find cost me £35, and you need one to test further. Easy enough to use, clip one lead to earth pin on plug and other to neutral pin, set to 250 volt and press button. One is looking for a reading over 1000000 ohms or one meg ohm.

But if you get some one in, maybe not only find the fault but can cure the fault.

Likely the problem is the mineral insulated heating element in an appliance. But really need to test, not change to see if that works.

Thanks, just had a look at them and pretty sure my father in law has one of them so will have a word with him.

I actually think ive narrowed it down the washing machine anyway. I used the dishwasher this morning and kept the washing machine off.

As I was passing, I turned the hob on again and all was fine. So went to the socket to turn the washer on and RCD tripped straight away

 

[adzyp]

There seems to be two options, get some one in, or DIY, and not sure which is best or cheapest?

A insulation tester cheapest I could find cost me £35, and you need one to test further. Easy enough to use, clip one lead to earth pin on plug and other to neutral pin, set to 250 volt and press button. One is looking for a reading over 1000000 ohms or one meg ohm.

But if you get some one in, maybe not only find the fault but can cure the fault.

Likely the problem is the mineral insulated heating element in an appliance. But really need to test, not change to see if that works.

Managed to get my hands on this today. He has this one https://amzn.eu/d/aFeNWvs

Not had much chance yet, but checked a few appliances. Plugged the lead into the E and L sockets and clipped to Earth and Neutral pins. Pressed the button and bar a very brief random number showing it then sticks on 1 MOhm.

Assuming ive done it right, does that mean those appliances are fine?

What would a faulty one show?

Thanks

 

[ericmark]

Testing neutral to earth is the main thing, as tripping with nothing turned on, and 1MΩ is a pass would would expect higher.

 

[adzyp]

Testing neutral to earth is the main thing, as tripping with nothing turned on, and 1MΩ is a pass would would expect higher.

Ok thanks. Guess ill spend a bit of time tomorrow testing a few other plug in appliances and see if anything jumps out