Warmup Underfloor heating issue

Hi all, just signed up as I’m at my wits end and going mad as feel no one believes the issue I’m having.

The set up

We have Warmup electric underfloor heating, which is split into 2 zones, hall and kitchen, both have 4ie thermostats. The kitchen totals 3150 watt, 13.125amp and the hall is 2000 watt, 8.33 amp so both within the Heaters Max 16 amp. They are on separate circuits on the consumer unit, with the hall on its own MCB, whereas the kitchen shares it MCB with some other kitchen appliances, notably the fright freezer, washing machine, tumble dryer and some sockets. Also on this consumer unit is ring main for other rooms in the house, such as TV, bedrooms etc

FWIW other kitchen items such as ovens, microwave, dishwasher are on a separate consumer unit.

Installation was 3 years ago and for the most part the system works fine. Both zones warm up, admittedly not as quick as we had hoped but the tiles that were laid on top were pretty thick but were underfloor heating approved.

The Problem

Last winter when we had the cold snap a couple of times the RCD on the consumer board tripped. I felt it was a result of the underfloor heating but if left them on 24h a day the RCD was fine and no more tripping, but expensive and unnecessary . I spoke Warmup and our electrician (not the one who installed as he’s no longer contactable) both said it couldn’t be the underfloor heating as it wouldn’t warm up if there was an issue with the system.

Now as the weather has turned colder, I have programmed each zone to come on at their required times, but again the RCD trips usually around 5am when the each zone turns on, and when nothing else in the house would be active beyond the usual. If I turn one of the zones off completely the other warms up and the RCD is fine. If I try to replicate both zones turning on later in the day then its works fine, it only seems to trip the RCD when the outside temperature is colder (possibly as indoor temperature in the rooms are lower too). There has been the odd instance of the RCD tripping during the day, for instance a week ago when the outside temperature was around 4 degrees and both zones turned on for heating at same time and the washing machine was turned on, but a daytime trip happens but is inconsistent.

Diagnosis

Speaking to Warmup they suggested there’s possibly a power surge when both zones are turned on and warming up together, so suggested to set the timers so they don’t come on at the same time. Which we did, but still found system tripped early in the morning once both were on. I then set each zone to have completely separate times of operation, but as weather turns colder this isn’t ideal and defeats the reason for having heating.

Yesterday turned both on at the same time, set the thermostats high, even turned on the washing machine and tumble dryer to try and get the RCD to trip, but the system was fine. If I can’t recreate the conditions for when an electrician would come to test they will say everything is fine. There is no consistency in when the system trips the RCD, except maybe at some point in the night and when I suspect the ambient temperature either in the zones or outside is closer to freezing.

My wife works from home and cant risk the pc crashing from the power going down during the day if the RCD was to trip so have turned the hall off permanently but I’m being moaned at the house feels cold and we need to get this resolved.

Does anyone have ideas what could be causing this? How it might get resolved?

I’m genuinely at breaking point with this and would appreciate any genuine advice

From what you have described its sounds as though you have an arrangement where a single RCD is protecting multiple circuits. If so, issues of natural cumulative leakage across multiple circuits sharing the same RCD can cause all sorts of random issues that are very inconvenient to establish and resolve. As such it can be claimed that installations with multiple circuits sharing an RCD, do not comply with wiring regulation 314.1 (BS7671).

When was the last periodic electrical inspection done on the whole installation? and do you have copies of the multi-page report? (EICR). If a comprehensive check of the whole installation has not been carried out over the past 10 years, then I would suggest this would be the first step. It may be that another circuit has developed a leakage problem that combined with your higher power UF heating switching on, provides a N-E path sufficient to cause the RCD to trip. The current condition of every circuit and the operating characteristics of the RCD can all be tested and verified by a competent electrician with suitable test equipment. The results obtained may help to isolate certain items out of the equation, or give an indication of some underlying cable issues you are currently not aware of. A key bit of information with RCD tripping problems is the insulation resistance readings between the Live and Neutral conductors to Earth. If you don't have this information then you are working blind, a bit like playing 'Pin the tail on the donkey', You may get lucky but the chances are you wont.

Doc H.     

Could you post a picture of your fuseboard?

Maybe investigate getting these dedicated circuits onto their own rcbo's 

This is a tricky solution as nuisance tripping can be tricky to work out the reason.

Hope this helps 

Doc Hudson said:

From what you have described its sounds as though you have an arrangement where a single RCD is protecting multiple circuits. If so, issues of natural cumulative leakage across multiple circuits sharing the same RCD can cause all sorts of random issues that are very inconvenient to establish and resolve. As such it can be claimed that installations with multiple circuits sharing an RCD, do not comply with wiring regulation 314.1 (BS7671).

When was the last periodic electrical inspection done on the whole installation? and do you have copies of the multi-page report? (EICR). If a comprehensive check of the whole installation has not been carried out over the past 10 years, then I would suggest this would be the first step. It may be that another circuit has developed a leakage problem that combined with your higher power UF heating switching on, provides a N-E path sufficient to cause the RCD to trip. The current condition of every circuit and the operating characteristics of the RCD can all be tested and verified by a competent electrician with suitable test equipment. The results obtained may help to isolate certain items out of the equation, or give an indication of some underlying cable issues you are currently not aware of. A key bit of information with RCD tripping problems is the insulation resistance readings between the Live and Neutral conductors to Earth. If you don't have this information then you are working blind, a bit like playing 'Pin the tail on the donkey', You may get lucky but the chances are you wont.

Doc H.     

Click to expand...

Thanks, tbh most of what you say means little to me. The fact its tripping at random times makes me wonder if an electrician comes and tests they wont find a fault unless I can replicate the trip. it is feasible that different temps and weather conditions can affect whether the trip happens or not?? Surely if was any leakage it would be tripping consistently? 

With regards to inspection, never I suspect. The house is around 15 years old, the kitchen was replaced 3 years ago when the underfloor heating was installed and the electrics were wired up. I've never heard of having reports on household electrics.

Doc Hudson said:

From what you have described its sounds as though you have an arrangement where a single RCD is protecting multiple circuits. If so, issues of natural cumulative leakage across multiple circuits sharing the same RCD can cause all sorts of random issues that are very inconvenient to establish and resolve. As such it can be claimed that installations with multiple circuits sharing an RCD, do not comply with wiring regulation 314.1 (BS7671).

When was the last periodic electrical inspection done on the whole installation? and do you have copies of the multi-page report? (EICR). If a comprehensive check of the whole installation has not been carried out over the past 10 years, then I would suggest this would be the first step. It may be that another circuit has developed a leakage problem that combined with your higher power UF heating switching on, provides a N-E path sufficient to cause the RCD to trip. The current condition of every circuit and the operating characteristics of the RCD can all be tested and verified by a competent electrician with suitable test equipment. The results obtained may help to isolate certain items out of the equation, or give an indication of some underlying cable issues you are currently not aware of. A key bit of information with RCD tripping problems is the insulation resistance readings between the Live and Neutral conductors to Earth. If you don't have this information then you are working blind, a bit like playing 'Pin the tail on the donkey', You may get lucky but the chances are you wont.

Doc H.     

Click to expand...

So you have an upfront RCD, which means it will trip at anywhere between 22mA and 30 mA across all the circuits.

a fault on any circuit could be causing this, the underfloor heating could simply be “pushing” the leakage over the threshold to trip.

you need to locate a local spark who has an earth leakage clamp meter to check the leakage, then narrow down to circuits and do proper IR tests

one solution would be to replace the rcd with a 100a do switch and RCBO’s for each of the circuits ..... or a new unit.

if you go for a new CU do not agree to a dual rcd unit

Murdoch said:

So you have an upfront RCD, which means it will trip at anywhere between 22mA and 30 mA across all the circuits.

a fault on any circuit could be causing this, the underfloor heating could simply be “pushing” the leakage over the threshold to trip.

you need to locate a local spark who has an earth leakage clamp meter to check the leakage, then narrow down to circuits and do proper IR tests

one solution would be to replace the rcd with a 100a do switch and RCBO’s for each of the circuits ..... or a new unit.

if you go for a new CU do not agree to a dual rcd unit

Click to expand...

but, with my limited understanding, wouldnt this mean it would be tripping constantly not just sporadically and when it seems to be colder out.

can't seem to get a local sparkie to come out and test unless I can show the system tripping....

carter69 said:

Thanks, tbh most of what you say means little to me. The fact its tripping at random times makes me wonder if an electrician comes and tests they wont find a fault unless I can replicate the trip. it is feasible that different temps and weather conditions can affect whether the trip happens or not?? Surely if was any leakage it would be tripping consistently?   

With regards to inspection, never I suspect. The house is around 15 years old, the kitchen was replaced 3 years ago when the underfloor heating was installed and the electrics were wired up. I've never heard of having reports on household electrics.

Click to expand...

Domestic RCD's must NOT operate with a trip current of 15ma or less. But they must operate with a current of 30ma or above. Some appliances can have natural leakage which is why RCD's must be tested to confirm they are not operating oversensitively causing nuisance trips.

If you have never had the wiring tested, and you do not understand much of my earlier post then I would suggest you either get someone professional in to commence some proper inspection and testing, or just carry on guessing as you are at the moment, and put up with the inconvenience when it trips.     https://www.electricalsafetyfirst.org.uk/find-an-electrician/periodic-inspection-explained/

If you were purchasing a second hand car you cannot guarantee its reliability, But a valid MOT and service history will give a good indication of its condition.  Without any op-to-date test results, you have no idea of the condition of your wiring. So all your assumptions so far have minimal validity. You need some valid Insulation Resistance test results for all circuits that the RCD supplies.

I suspect your logic and assumptions about how RCDs operate is misguided causing you come to the wrong conclusions.  As an additional point to muddy the water for you, even if you turn the MCB's off, all of the Neutrals and Earths are still connected together inside the fuse box so a neutral to earth fault on any circuit can cause the RCD to trip from power flowing from any of the MCB's . (Which is why your fuse box is a poor design). As has been said there could be fault(s) on other circuits that individually will not operate the RCD but cumulatively do. 

Doc H.

I think you're looking at damp ingress.

carter69 said:

but, with my limited understanding, wouldnt this mean it would be tripping constantly not just sporadically and when it seems to be colder out.   
 

Click to expand...

No.

Have the RCD tested to make sure it can actually carry 16mA  without tripping.  (very quick job for an electrician)
Have an insulation test done on the heating system   (very quick job for an electrician)
Note that even if the RCD can carry 16mA without tripping 15mA can already be there from other 'leakage around the house (Immersion heater, washers, heating pumps, outdoor lights,  multi way adapters with surge protection in every room all being usual suspects alongside old/damp cabling) so some very minor electrical leakage in the 'New' UFH can be the final straw on the old situation.

As others have said if none of that solves it the pre-testing/testing that should occur with a Consumer unit upgrade to ALL RCBO is probably the best use of money and will likely find the problem and/or make it easier to identify future issues

.  

Doc Hudson said:

Domestic RCD's must NOT operate with a trip current of 15ma or less. But they must operate with a current of 30ma or above. Some appliances can have natural leakage which is why RCD's must be tested to confirm they are not operating oversensitively causing nuisance trips.

If you have never had the wiring tested, and you do not understand much of my earlier post then I would suggest you either get someone professional in to commence some proper inspection and testing, or just carry on guessing as you are at the moment, and put up with the inconvenience when it trips.     https://www.electricalsafetyfirst.org.uk/find-an-electrician/periodic-inspection-explained/

If you were purchasing a second hand car you cannot guarantee its reliability, But a valid MOT and service history will give a good indication of its condition.  Without any op-to-date test results, you have no idea of the condition of your wiring. So all your assumptions so far have minimal validity. You need some valid Insulation Resistance test results for all circuits that the RCD supplies.

I suspect your logic and assumptions about how RCDs operate is misguided causing you come to the wrong conclusions.  As an additional point to muddy the water for you, even if you turn the MCB's off, all of the Neutrals and Earths are still connected together inside the fuse box so a neutral to earth fault on any circuit can cause the RCD to trip from power flowing from any of the MCB's . (Which is why your fuse box is a poor design). As has been said there could be fault(s) on other circuits that individually will not operate the RCD but cumulatively do. 

Doc H.

Click to expand...

Thanks, appreciate the advice. Never heard or know of anyone who has had period inspections, appreciate people on this forum are an exception, but have read the link and will get someone in asap. Surprise the electrician we have used before hasn't suggested it rather than ask me to see if I can isolate the issue myself!

better find a new electrician...

carter69 said:

Thanks, appreciate the advice. Never heard or know of anyone who has had period inspections, appreciate people on this forum are an exception, but have read the link and will get someone in asap. Surprise the electrician we have used before hasn't suggested it rather than ask me to see if I can isolate the issue myself!

better find a new electrician...

Click to expand...

I think that speaks volumes of the lack of competence of your previous electrician asking you to isolate it yourself.  As another point for your reference, one of the reasons that you were not aware of the recommendation for routine electrical inspection is because the wiring regulations BS7671 are non statutory. Just guidance for good practice, and DIY electrical work is legally allowing in the UK, so it is not uncommon for many aspects of good electrical design, installation, testing and documentation to be overlooked within domestic installations. In the work-place and other public venues, various statutory laws come into play putting more of an obligation upon proper electrical testing. (e.g. Pubs and venues requiring entertainments licences would need valid electrical certificates to comply with the terms of their licences).

Where about in the country are you? we may have a forum member able to offer you assistance.

Doc H.      

carter69 said:

but, with my limited understanding, wouldnt this mean it would be tripping constantly not just sporadically and when it seems to be colder out.

can't seem to get a local sparkie to come out and test unless I can show the system tripping....

Click to expand...

The key benefit of rcbo breakers is that only the affected circuit would trip, not the whole board

Why don't you post your location and see if anybody on here is local to you?

When the kitchen was done three years ago didn't the electrician point out the inadequacies in your present distribution board?

or the fact that it did not comply?

kerching said:

When the kitchen was done three years ago didn't the electrician point out the inadequacies in your present distribution board?

or the fact that it did not comply?

Click to expand...

The Plumbertrician you mean ?

Bruspark said:

The Plumbertrician you mean ?

Click to expand...

Or possibly, BuilderPlumbKitchenfitterTrician ?

Doc H.

Do they ever trip out when warm  ?  

As a side issue ,    remember that floor heating needs some  time  before you feel the benefit   , no good thinking we'll have it on  for an hour  tonight .   See if you can find Manufacturers Instructions  online  for guidance  on warm up times.    

If you post up your location one of might be either near or know someone reliable who could take a look for you?

Morning, various comments to come back to overnight

Kitchen electrics were done by a separate electrician the kitchen installer employed, he also connected up the UF heating. He put the kitchen appliances on 2 separate ring circuits for the kitchen on another consumer unit we have with brand new breakers, have had no issues with them or that board. No inadequacies in our current board were highlighted by that electrician or the one we have used for other matters.

The UF mats were laid by the tiler and were resistance tested prior to the floor being laid.

"The key benefit of rcbo breakers is that only the affected circuit would trip, not the whole board" agree totally and something I suggested to my electrician as it wouldn't fuse the whole house plus it might help identify which of the 2 zones is causing the issue. I actually was considering replacing the wall fuse spurs with ones with RCDs, to see if prevented the unit tripping, but now going down the more thorough route I'll leave to the experts.

"Do they ever trip out when warm" very rarely or if ever, most consistently when starting up early morning when colder out. Did have an instance a week ago when tripped at 4:30 pm, both were warm and we'd just come home, the hall had been on and the kitchen timer just clicked on as well that day it was bitterly cold out. I swear we only have an issue when the temp is lower, the other day it was 9 degrees, no issues, this morning at 4 degrees am sure if i had both zones on it would've tripped.

I'm based on North West London and overnight have found a couple of approved electricians who will speak with today to follow up with, but if any of you are local who would like to help resolve this mystery please let me know. Thanks