Electric Boiler tripping off RCD?

Here is a link to pdf of your boiler,

https://www.dlmanuals.com/manual/gabarron-mattira-mac15/installation-instructions-and-user-manual/11

see page 37 shows the element layout and two chambers shown for DHW and seperate for Hot water, obviously which elements are switched on depends on your power setting from the control panel, each chamber has 6 elements individually controlled by software program but the faulty element gone down to earth leakage tripping RCD can be isolated. those who might say it cannot be done or is a dangerous solution obviously do not possess the knowledge to say the least.

Dear Mike,

Thank you for all the information and detailed advice - most appreciated indeed.

Our flat is 2 minutes away from Kings Cross station (British Library exit) in London. Please text me @ 07785526924, thank you.

Best / Xiaolei

Nice to speak to you, Xiaolei, I hope it will get resolved on Tuesday, if not give us a call. Thanks ,

For those interested, the elements are housed in two seperate chambers, one for DHW and one for Heating, so no need for a heat exchanger, Both under pressure, so replacing any heating elements means draining the boiler after isolating heating circuit, and turning mains water and electrics off,
I also spoke to manufacturers technical help line, the elements for each chamber come on a single block of 6 elements, so replacing one element means replacing all 6 elements on a block, however I suggested to Xiaolei if she did not want to be ripped off she can isolate the defective element and tuck its wires safely.

Reply to the comment left by Xiaolei at 08/02/2022 - 12:47
Reads electrical are very well recommended
https://readselectrical.com/welcome

It sounds like you may be on the road to a solution now but just in case you still need help you might consider posting a message on the forum here:

https://www.electriciansforums.co.uk/

It is worth observing that an electric boiler is basically the same as an electric kettle or even an electric oven (no water (bit of steam maybe), but operates at a lot higher temperature) and it is typical for the heating elements within these appliances to fail with an earth fault to neutral as has already been mentioned by a number of contributors.

But this is not the only possibility.

There have been several mentions that the boiler concerned is on it's own RCD but I wonder if this is actually true?

Certainly, such a load should have it's own distinct MCB, but a separate RCD is much less likely.

A picture of your consumer unit with the flap open could assist here. Try to get a well focussed one with readable labels on it.

When the trip pops do you lose any other things - socket circuits (lighting even)? If so then this implies a shared RCD.

Secondly, the problem may not be with the boiler at all and may in fact simply be the accumulation of the (normal) earth leakage currents adding together to exceed the trip threshold of a shared RCD. This is not as rare as it might seem and ensuring that your electrician rules this out first could save a lot of money.

Basically, I am echoing Paul landlord's advice here.

It can be frustrating, but if you are in a shared RCD situation it is possible to work out for yourself whether the problem is an accumulation of earth leakage currents. Try to spot any patterns - does it only happen when the microwave / washing machine / dishwasher / whatever is running? It doesn't have to be one of these typically high-current appliances. It could just as well be the accumulation of leakage current from many smaller devices - especially gear with switched-mode power supplies in them (which is basically almost everything else these days - even some microwaves!)

Any electrician worth his salt these days ought to be able to measure the earth leakage current that is actually flowing in your installation and this will dramatically speed up the time to diagnosis the faulty item.

If it an MCB and not an RCD (these two items are often confused for one another by none experts) that is actually tripping then you either have a fault on the boiler itself (most likely) or on the circuit (fixed wiring) feeding it (less likely).

When I spoke to this lady, she explained to me how she and her husband chose to go for electric boiler as that was what was being seen as thing of the future to cut down on gas boiler emissions, so she could very easily have had a gas boiler installed.

Then when she did her research, on what was available, she chose this particular boiler, then she ordered one and it got delivered, she could not find anyone competent enough to install it, no one what so ever, even the manufacturers could nominate any engineers, this was 4 years ago, situation may be a little improved now, there may be half a dozen engineers doing it.

There is nothing particular about using electric boilers as opposed to gas boilers, in fact if anything they are more simpler to install, the only critical part being the supply and its cable, we are talking of over 65 amps and if you add an electric cooker and oven so you could be limiting the meter's ability to meter nearly 100 amps, and greater risk of meter going up in flames!

So finally after months went by, she managed to find one gas safe engineer who was persuaded by them to at least hang the boiler up and install the radiators, he was given all the manuals and phoned manufacturers technical help line to get as much info, so he finally managed to run it set at 8Kw heat setting for both hot water and heating, it just takes a bit longer and is much safer not to run it at max.

So it was after 4 years that it started to trip RCD, she could not get hold of that original installer as he had shifted to another far away location. Moved out from overcrowded London.

So she got hold of one electrician, who came and looked at it and said he was not too comfortable to deal with it, he did manage to isolate individual elements and took earth leakage reads, and had tried to check those reads with the boiler distributors technical help line, but after staying on the phone for nearly half hour he gave up and had to attend another emergency.

So this is how she rang a few more gas safe engineers, all were not confident when she told them it is an electric boiler, most did not sound competent enough when she asked them if they had carried out any previous work on electric boilers, so this is when she came here to seek our help.
I could do this job for her,but I absolutely hate getting into central London, not only I may have to pay congestion charge, as well as ULEZ charge, so it is a nightmare , nor do I think it will be fair for me to get there in a taxi, that would most probably cost more than what I might charge for the repairs, a block of 6 elements cost just under £100 including its gasket and is easily changeable as the access is from below and easily replaced.

So finally she managed to get someone who would be coming to see it on Tuesday and if he does not get any luck, I will have to hope on a train and see what i can do for her, there is nothing I cannot fix accept bring a dead frog to life again.

Very interesting. Just quickly read the manual that was posted on here. as a gas safe and NICEIC contractor, i used to do a mix of electrical and gas heating and boilers, so i can see why some gas and some electrical engineers would hesitate. interesting, my public liability insurance had to specify whether i was doing plumbing or electrical work - they considered plumbing as higher risk! As this electrical work involves draining the boiler, some electricians would hesitate. From experience, even changing immersion heaters in a normal cylinder can land you in trouble!
Yes, we need multi-skilled engineers; not sure the colleges are providing the necessary training, and with the increasing regulations for the two industries, it can be an expensive process to qualify in both.
Sadly, advice is to keep things simple, at least until the manufacturers can provide trained engineers to maintain these technologies. Heat pumps are another issue!

Hi Xiaolei and Mike
Do you know how the tenant fared with the electric boiler, regarding running costs and whether it affected the EPC?

If an ASHP reduces it, I would think using peak electricity with zero CoP would drop it significantly.

If the maximum power on single phase is 12kw and a typical supply is 100A, about 23kw, that wouldn’t leave much for oven, hob, EV charging, shower if electric, or microwave 800w takes about 2kw input.

And 12kw is £3-30/hr or £2,800pa for a typical low-use (10Mw pa) consumption at April’s SVT! Which most of us will be on by any Fixed Deal ending or our supplier going bust. ☹️

@ Richard Cordwell, thank you so much for the recommendation - I will contact them on Monday and find out what they can do in relation to electric boiler and underfloor heating - now we have much better idea what is needed.

@Badger We are still waiting for the person of manufacturer’s referral to come on Tuesday but to be honest we don’t know what to expect from him - he is the owner of a business that has the after-sale service contract from the manufacturer, but his background is in business development and management, not a NICEIC or GAS safe registered engineer.

We are very impressed with your experience: you were right in questioning whether the boiler concerned is indeed on it’s own RCD - I thought it was as I had seen underfloor heating on a separate RCD. But on further investigation, the separate underfloor heating RCD refers to the electric underfloor heating in our bathroom, not the central (underfloor) heating for the flat. The boiler and the manifold for underfloor heating of the flat is on the same Central Heating RCD. So as the boiler trips the RCD, the underfloor heating in the flat is dead too.

You might also be correct to suggest the problem may not be the boiler - there might be a slim chance for the underfloor heating to be at fault as the underfloor heating had tripped off manifold (not RCD) two months before and was fixed by the heating engineer.

All other appliance are on separate RCD. Central Heating RCD only trips off as soon as the boiler is on. When the boiler is off, the RCD can be switched back on and all the electrical in manifold for underfloor heating is back on, but as soon as the boiler is switched on, the RCD is tripped off - this is why the underfloor heating engineer thinks it was the boiler that at fault.

I have taken a photo of our consumer box, but sadly I couldn't attach picture here to show you. Sorry.

@Mike, We are most grateful to you for all the help you have provided. We completely understand your dislike traveling to central London and will keep you posted about our progress.

@Ararat: thank you for sharing your insight and wisdom - we didn’t know better and ended up having to deal with more than what we could comfortably handle. Keeping things simple would have suited us to the ground, we just didn’t know how to. Any suggestion for the best electric boiler and/or central heating system for future ?

@Chris Byways: We don’t know the details of the running costs for the boiler. We have booked EPC assessment two weeks ago but had to postpone it due to flat without central heating now. So updated EPC since the electric boiler was installed in late 2017.

It has become increasingly clear now that we need an experienced NICEIC and GAS safe heating engineer to check the electrical set up of our boiler and underfloor heating, identify the root cause to boiler tripping off RCD and rectify where necessary. Any recommendations of such multi-skilled and talented tradesman would be most appreciated indeed.

Thank you and best wishes,
Xiaolei

Corrections:
@Badger: I don't know how to upload pictures here.
@Chris Byways: No updated EPC since the electric boiler was installed in late 2017.