Discuss 30ma rcd tripping after replacing consumer unit in the Electrical Forum area at ElectriciansForums.net

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muzza1

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Hello all, how are you?
I often look on here but the time has come to ask for some advice!
Nearly finished some alterations in a customers Kithen, Dining room, Utility room and Garage. Approx 3 days work in total.
Anyway, after all 2nd fixed and new split load board installed pop goes the rcd! Proper annoying!
It was found that when the ch+hw boiler was switched on at the spur it tripped the 30ma rcd on the split load board, here we go, i thought :sad:
Explained to the customer the situation and after bypassing the rcd hopped in the van knowing Monday is going to be a headache, (can't stand fault finding!)
To try and cut a long story short, i was after some advice or ideas re how to get round this problem without some testing deep within the customers boiler etc with certification and notification in mind!

I hope i've made some sort of sense with my question!

Thanks for any help on this chaps.
 
Hello all, how are you?
I often look on here but the time has come to ask for some advice!
Nearly finished some alterations in a customers Kithen, Dining room, Utility room and Garage. Approx 3 days work in total.
Anyway, after all 2nd fixed and new split load board installed pop goes the rcd! Proper annoying!
It was found that when the ch+hw boiler was switched on at the spur it tripped the 30ma rcd on the split load board, here we go, i thought :sad:
Explained to the customer the situation and after bypassing the rcd hopped in the van knowing Monday is going to be a headache, (can't stand fault finding!)
To try and cut a long story short, i was after some advice or ideas re how to get round this problem without some testing deep within the customers boiler etc with certification and notification in mind!

I hope i've made some sort of sense with my question!

Thanks for any help on this chaps.

Did you do any testing at all on your work before energising or just switch on and hope for the best ?
 
No testing then, serves you right, got yer tin hat on yet? and I was being kind, wait for the flak that's a coming your way
 
How exactly did you bypass the RCD?

There's hardly a lot of fault finding to be done is there, you already know it's in the boiler controls somewhere. It's hardly going to take you long to go through a domestic boiler circuit, is it a combi or heat only boiler?
If the fault proves to be internal to the boiler you'll be looking at getting a plumber out to fix it, and if you didn't have the sense to add a suitable disclaimer to the quote/contract then you might be paying for it.
 
i would disconnect heating system at fused spur, test up to that point prove all results, then speak with client about a fault on the heating system should the fault be after the fused spur. should it be on the supply up to fused spur then sort it out with them.

heating system if not a combi

disconnect boiler
disconnect pump wiring if not in boiler
IR test pump to earth
If pump IR test 0M ohms or there about's faulty pump
remove programmer cover bridge out L to no 3 & 4
turn up thermostat & cylinder Stat
IR test on secondary of the fused spur that you disconnected (boiler still not on circuit)
LN-E see if you have 0M ohms or close to it or clear
then open valve manually
same IR test
should show all the way to boiler.
if all clear above then put back together & would probably tell you that fault is in the boiler.

the above is for 230V controls & not low volt.
should you have a system's boiler you can probably unplug the pump & test it inside the boiler.

if you can't understand any of the above you are probably out of your depth & should consult your client to get someone in who can fault find on an electrical system.
the above is a basic heating system layout & may not cover every variation but it is a start for you.
good luck
 
Last edited:
Didn't do any testing prior to working on the ring main, getting complacent.
The original wiring is only approx 15 years old and not been messed about with so took it for granted that i shouldn't come across any problems.
After replacing board and identifying fault just supplied the ring from the 1st way next to the main switch, non rcd protected.
(Obviously i realise this can't be more than temporary)
To be honest i think i need to take a step back at the beginning of each job from now on and concentrate on doing some testing before getting the tools out and just cracking on! There's no way i can sign this job off until boiler fault is sorted, but as this spur is back to back with the cu any ideas on possibly feeding spur via 5amp radial non rcd protected from board.
It's a standard fully pumped ch system with 3 port etc.
I'll get cracking on with testing as much of the heating system as i can and hopefully will be able to crack it without calling a Boiler engineer, looks like being an interesting Monday morning!
 
Thanks for your post marc8. I'll test the system in that order and let you know how i got on.

A bit of a wake up call to how i go about my work me thinks.
 
You could possibly feed the boiler circuit from a non RCD circuit if certain criteria are met BUT that isn't an alternative to methodically finding and rectifying the fault. Check through the wiring associated with the boiler and controls and take nothing for granted - but also carry out the full testing on the ring just to make sure nothing is fooling you.
 
Not doing test results till tomorrow, kicking myself now as this problem could easily have been identified prior to adding to the circuit.
 
Yes, re energised the circuit which i should have tested first. Have you ever energised a circuit without testing it?

This ain't no wind up, just felt like seeking a bit of advice before going back to work tomorrow.
 

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