Electric Boiler tripping off RCD?

Reply to the comment left by Xiaolei at 14/02/2022 - 02:48
Electrical underfloor heating - hmmm....

I don't recall this being mentioned in this thread until now.

Personally, I would be very suspicious of this indeed - especially as it has seen recent attention from a repairer.

What happens if you turn the underfloor heating off and then turn the boiler back on?

Does the trip still pop now?

Thanks for update, lots of useful info on this thread, probably an element but could be the under floor, or even wiring or possibly cumulative. Rule nowt out.

Off topic but this was very useful for Electric Boilers and EPCs https://www.thepropertyac.com/domestic-epc-advice-electric-heating-system/

no need for Gas Safe registration as it is not gas, but a good plumber may be needed if it is underfloor heating with water fed from boiler. Why the RCD is tripping needs to be narrowed down by an insulation test - as the others have said, more than likely the elements.
We have fitted the Amtec boilers, now under the Heatrae Sadia brand name, with success so far - no call backs yet after about 10 years for our first one. I am not familiar with the make of boiler you have, but it seems quite complex.
But the heaters for fresh hot water can be troublesome in hard water areas, maybe the scale or chemicals in the water, we ended up replacing with Incoloy and Titanium ones, and again never had to replace one yet. The plain copper elements that the manufacturers originally supplied had a short life in our area, west London.

@ Badger, we have one RCD for the bathroom which has electric underfloor heating and a towel rail. This underfloor heating has never had problem.
The rest of flat has another "wet underfloor heating" connected with the electric boiler - The RCD for this system is now tripping off. One of the many tiny fuses in the manifold for this underfloor heating had blown twice some two months ago, and has been changed by the ufh engineer. The underfloor heating seems to work fine since.
However, I can't switch off the underfloor heating with the boiler switched on - looks like the underfloor heating shares a big switch with the boiler leading to a RCD in consumer box labeled "Central Heating". The reason I can switch off the boiler individually is because the boiler has its own in-built switch on/ off unlike the ufh.
I wish I could upload pictures to show the set up but this forum doesn't have the facility.
@Chris Byways Thank you so much for the link - it never came to our mind to engage a domestic EPC assessor to model a plan for our property and provide a predicted EER before we decided to change and install electric boiler. Such a smart yet easy move, we will surely bear this in mind for our next renovation.
@ Ararat, thank you for sharing your experience - as you have probably sensed, we were (still are) a relative novice as far as property is concerned - a steep learning curve all along !
We are overawed by the sheer amount of knowledge and experience people have here and are most grateful to all responses and replies to our problem. Thank you all so much and I will keep you updated.
Best wishes,
Xiaolei

Just a little update on her heating problem.
She sent me pictures of her consumer unit, all circuits are protected by individual Hager brand 30mA RCBOs.

So there is no question of cumulative earth leakage currents tripping a master RCD, there isn't one.

Her electric underfloor heating is working in her Bathroom and her kitchen and hallway, so not a problem with that.

It is only her wet water heating that is problem, so highly likely it is in the boiler, and likeliest culprit to be elements, two sets of elements so which one we don't yet know but she thinks it was the Heating circuit (CH) and not the DHW, reason she thinks it is CH set of elements is because when she goes away for a few days on end, she turns off her Hot water tank within the boiler, and leaves under floor wet heating on, so it was during one such away visit that when she came back her 40Amp RCBO for her Boiler had tripped.

So hopefully this new engineer coming to see it will have diagnosed her problem and hopefully he will have spare set of elements and can do the job all in a day, hopefully he won't have to come back with a new elements to be ordered since he is one being sent by the boiler supplier, he should carry basic parts that are most likely to be required on these boilers. So hopefully it gets sorted in one visit.

Dear all,

An update of the latest with our Elnur Electric Combi boiler Mac 15.

Due to availability / logistic constraint, we first engaged a Gas Safe Heating (Boiler) Engineer to check the boiler which came to no avail.

We then arranged our trusted electrician who had no boiler experience to come and check the heating system - the RCBO in the fuse box is intact and an element on the heating block is at fault.

Our boiler is now up and running with 5 elements instead of 6 i.e. the faulty element has been identified and isolated and, for now it seems working fine.

(NB: the maximum output capacity of our boiler is 15 kw and we have set it for 8 kw only so one element down seems to cause no issues).

Thank you all so much for your generosity with time and effort trying to help us resolve our boiler issue. I am most grateful for all the advice received.

Thank you and best wishes,

All our best wishes,

Exactly what I suggested your electrician could have done by identifying the culprit element and isolating it, to get you going for now, it may run good for a few more years before another element goes, but at least you know who you need to call next time. I hope you were not charged too much for this. Keep your fingers crossed for now.

Dear Mike,

Yes, indeed.

Our electrician has been both trustworthy in his work and reasonable in his pricing. We are very happy with him.

Thank you and warm regards,
Xiaolei