Discuss Boiler fault and rcd tripping? in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Bob Geldoff1234

-
Esteemed
Arms
Reaction score
765
I got called out to house a few days ago with the main rcd tripping when they turned the hot tap on with the combi firing up.They had only just had the new boiler fitted and the tripping had started straight after it was installed.
I IR'd the boiler circuit(which was wired on its own 16amp breaker) and got>200 megohms across live,neutral and earth.
I then tested the rcd with trip times of 28ms and 10ms for x1 and x5.The ramp test gave 27ma trip.

I then tested the remaining circuits and all of them were clear except one which had a live and neutral to earth reading of 4 megohms.

I had a look at the boiler spur connections and inside the boiler.All perfect.
So,seeing as only one circuit(downstairs sockets) was generally low i moved that circuit over to the non rcd side and fitted a 30ma rcbo to see if that would trip.
I got a call the following day to say that the main rcd was still tripping.
So i went back and reinstated the down sockets back onto the rcd side and moved the boiler circuit over onto the rcbo.
I was expecting a call to say that the rcbo was now tripping and at least i would be able to narrow it down as to which circuit was causing it.
It has now been a few days and neither the main rcd or the rcbo has tripped.

Any ideas why this could be?

One theory is that some electronic circuit in the boiler was upsetting the main rcd and by moving it to a different type and make it now doesn't trip that breaker?
The other theory is the cumulative leakage of the socket circuit and the boiler supply was enough to trip the rcd?

Because the fault is intermittent and the readings are generally above the rcd tripping threshold then this is why i have had to revert to trial and error to find the which circuit is causing it?

Anyone else had this sort of fault before?
 
Only issue i have had is with water getting into the zone valves. Sometimes when a boiler is changed water is released and goes everywhere (in my experience anyway) - it could be that when this boiler was changed then any electrical device south of the boiler could be damp and trying to dry out.
 
My guess
When its grouped with others on a rcd and there is a neutral earth internally to the boiler,other circuit loads finding their way via that route may cause the tripping
When the boiler is on its own trip the fault remains but the leakage current may be too little to cause it to trip
 
Ive had a similar issue on a new boiler recently, the issue turned out to be a seal on the flue.

The condensation was was getting into the central part of the flue and dripping back onto one of the connectors on the boiler, after a hour or so the problem would disapear, boiler tested ok every time we went to test it, on the second visit I noticed a small rusty water stain which lead me to completely stripping the boiler apart to find the fault.

Maybe worth a look.
 
Might have a neutral caught by a box elsewhere on the circuit only trips when something draws a load have had similar in the past but a bit of testing should show the way.
 

Reply to Boiler fault and rcd tripping? in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock