CH Boiler tripping RCD

[Kaymo]

Hi,
Wasnt sure whether this should go in plumbing or electrics, suppose it depends on the eventual cause!

I've just fitted a consumer unit with split load and two RCD's. Currently the only circuit that is wired to the 2nd RCD is a circuit which includes the CH boiler. This RCD is tripping intermittantly and appears to be the boiler which is the cause.

Strangely, if I turn on the RCD it holds for a few seconds before tripping. If I then turn off the switch on the spur for the CH, and then switch on the RCD and then turn back on the CH switch the RCD holds for hours before randomly tripping again. During this period the CH and hot water both work and yesterday RCD held for at least 6 hours before tripping some time during the night.

The boiler is new and I can get the guy who installed to come back out and look at it but wanted to make sure that there is nothing wrong with the circuit supplying it first. I would have thought from the sequence of events decribed above and the random tripping that it is more likely to be something in the boiler?

Anyone have any ideas?

Thanks in advance.

 

[yorkspark]

Picture of db with cover off would be good, doubt it will be the boiler more likely a termination error.
can you post a picture of the eic results page for the testing so we can look at the results.

 

[securespark]

What's the IR test result for that circuit, with all loads disconnected?

 

[PrenticeBoyofDerry]

As above we need the Insulation resistance test of the circuit.
Disconnect the boiler either by the plug or open the switch on FCU and remove fuse and any other items that are connected to the circuit.
Then give us the test results, also check the flex on the boiler for damage.

 

[londonboy]

Assuming all testing procedures were followed correctly:

Suspect pump, valve or fan.

 

[Kaymo]

Thanks for the replies.

I dont have the equipment to do IR testing etc. I am making a presumption that as I can only reset the RCD after switching off the switch on the CH spur that the fault is most likely to be in the boiler or the circuit from the spur to the boiler - does this logic seem sound or is it possible that the fault could be before that in the wiring from the CU?

If the fault is in the boiler or the circuit from the spur then I will be calling the guy who fitted the boiler as it was only fitted a couple of months back. Seems like the fault was already present and fitting the RCD has brought it out.

It just seems strange that when it trips the RCD only resets when the switch for the CH spur is open, but once you reset it you can close the switch and it works fine. Hasnt tripped since I reset it this morning.

 

[EFLImpudence]

I dont have the equipment to do IR testing etc.

Oh! What a pity - never mind we only test circuits for fun, anyway.

If the fault is in the boiler or the circuit from the spur then I will be calling the guy who fitted the boiler

Oh dear. If only you had tested it properly then you would be able to tell him for sure.

as it was only fitted a couple of months back. Seems like the fault was already present and fitting the RCD has brought it out.

Oh dear. If only you had tested it properly then you would know.

It just seems strange that when it trips the RCD only resets when the switch for the CH spur is open, but once you reset it you can close the switch and it works fine.

It is strange. If only there were a way of testing it.

Hasnt tripped since I reset it this morning.

Well, there you go. It must be cured.

Anyway - 10/10 for shamelessness.

 

[PrenticeBoyofDerry]

I've just fitted a consumer unit with split load and two RCD's.

Kaymo
Even in Lanarkshire, you can't just fit a new CU's without doing some comprehensive testing!
If you don't do the testing how on earth do you know that the installation is safe?
Do you have continuity of main earth bonding?
Have you got a good, if any continuity of R1+R2 or R2?
We know you don't know the IR!
Is polarity correct?
Do you know your Ze reading
Do you know if the Zs/disconnection times are compliant?
What is the PFC?
Do you know if the RCD is functioning within it's permitted time and its permitted range?

I guess the answer are all no!
Absolute crazy!

Did you fit the boiler too?

 

[londonboy]

Ah yes this was the guy who wanted his cut out and CU within the bathroom, well I guess this has been ignored, and he's moved the CU himself.

Another 5 minutes of my Sunday wasted replying to someone doing something dangerous and illegal.

 

[Kaymo]

Well guys, thanks for all the sarky unhelpful replies. Please remember that this is a DIY forum so it is quite possible that people asking questions on it might be doing DIY. If you want to reply and be helpful then I appreciate that, if you think its a waste of your time, dont reply - dead simple.

As far as the 'dangerous' installation, given that the electrical installation is exactly the same as it was last week except that the RCD is now fitted then its clearly now safer than it was.

 

[PrenticeBoyofDerry]

Well guys, thanks for all the sarky unhelpful replies. Please remember that this is a DIY forum

You are doing work outside of the scope of DIY, that is why you have a problem!
and please take note that it is illegal to fit a CU without notification to Building controls. Which will require schedules of inspection, tests with and an EIC.

As far as the 'dangerous' installation, given that the electrical installation is exactly the same as it was last week except that the RCD is now fitted then its clearly now safer than it was.

Prove it, test results please prior to your installation and as it stands at this time. You have also got a faulty that was not there previously.

if you think its a waste of your time, dont reply - dead simple.

If you think it's a waste of your time asking the question, don't ask them!
You have already been given very good and helpful advise, that would have continued but you can not give us an IR test on the circuit, how do you expect to receive help? Guess
Be honest with yourself mate, nothing sarky about it!

 

[bernardgreen]

As far as the 'dangerous' installation, given that the electrical installation is exactly the same as it was last week except that the RCD is now fitted then its clearly now safer than it was.

If the new RCD is tripping then the existing wiring may have a fault on it that until now has gone un-noticed. That fault is still there otherwise the RCD would not be tripping would it ?

RCD do NOT ensure safety, they only reduce the hazards of earth leakage, a fatal shock is still possible with an RCD fitted.

Neither do they protect against over current. You have changed the CU so you will have changed the fuses or MCBs. They are the over current protection and in you have fitted the worong rating ( amps ) or type for the cables you may have reduced the safety of you house when a fault happens.

 

[Kaymo]

Bernard,
I am aware the fault was still there, my point was that by fitting the RCD CU I have made the installation safer and brought out an existing fault that I otherwise wouldnt have known about. I have kept all of the fuse ratings the same or less for each circuit.

PrenticeBoy,
I dont have a fault that was there previously, the fault was there all the time and as I said above by fitting the RCD I have found a fault that I wouldnt have otherwise known about.


Anyway, I found the fault. It was nothing to do with the boiler, I had switched that off yesterday and the RCD tripped again overnight. I followed the circuit down and found an old fashioned fusebox with wire wound fuses under the house. The main switch on this was very sticky and it looked like someone may have greased this at some point in the past and that could have been where the leakage was. I have replaced this and RCD has not tripped since.

I am not doing this work because I want to, its not a hobby. If I had the money I would love to be able to pay an electrican to come out and do this but if I called an electrician they would, quite rightly want to rewire the whole house and that is not money that I have. In the year that I have been here, I have already had to shell out £3k for someone to fit a new boiler amongst various other things. Fitting the RCD myself is better than none at all. I've worked in electrical maintenance in industry and I fully understand the concepts involved.

 

[securespark]

Bernard,
I am aware the fault was still there, my point was that by fitting the RCD CU I have made the installation safer and brought out an existing fault that I otherwise wouldnt have known about. I have kept all of the fuse ratings the same or less for each circuit.

But if you have not tested, then you may have fitted (for example) a 32A MCB to two 2.5 cables that is not a ring final, which is dangerous.

I appreciate that you have not made it any less safe, but that does not excuse you! You need to ensure the safety of yourself & others by having the install tested and made safe where necessary if you cannot do it yourself.

I've worked in electrical maintenance in industry and I fully understand the concepts involved.

Apart from inspection, testing & certification. Did you do those when you "worked in electrical maintenance in industry"?

 

[PrenticeBoyofDerry]

I've worked in electrical maintenance in industry and I fully understand the concepts involved.

So you should know the values of testing then?
I am not knocking you for doing the install, whether it be a matter of saving money or even that you feel confident in doing the work and thought you would have a go.
What I am knocking is the fact, you did not test the system before or even after the board change, then claimed it was safe or safer, without having any evidence to back this up.
Also that you were offered help, but you could not give anyone anything to go on. Then expected the problem to be solved.