Combi tripping RCD in heating mode only

[martygturner]

I would get the earth bonding on the pipe work checked for a small leak of current. I had a tripping boiler in a tenanted flat that turned out to be a leak from the sparker

 

[JohnW2]

What I can't understand is why you would wait 2 years to fix this, what are you not telling us.

He's told us that he's been trying to get it fixed throughout that period and that, despite numerous Baxi engineers having attended (and have "... pretty much replaced everything in the boiler) he has "had no heating for 16 months".

I don't think he has been "waiting for 2 years".

Kind Regards, John

 

[plugwash]

How are the heating controls wired up? One possibility is that sum numpty has taken feeds for different parts of the heating system from different circuits.

 

[ericmark]

How are the heating controls wired up? One possibility is that sum numpty has taken feeds for different parts of the heating system from different circuits.

I considered that, but he says the thermostat is wireless.

 

[baldykev]

need to measure your earth leakage with out boiler on. you may find some other fault is casing a high earth leakage and when boiler is on CH that's just enough to trip RCD

 

[ericmark]

need to measure your earth leakage with out boiler on. you may find some other fault is casing a high earth leakage and when boiler is on CH that's just enough to trip RCD

Also my thoughts, I wonder if the extra current when running central heating could highlight a neutral to earth problem, I have a clamp on now which can measure the leakage, seen to right, but for many years only had the one to left, which would measure in 0.01 amp increments, the new one to right measures in 0.001 amp increments, and also DC amps, and at nearly 4 times the price one can see why boiler engineers may not have the instrument in their test kit.

I know the total leakage for my house is around 20 mA, as this is split between 14 RCBO's it is not a problem, but many homes only split between 2 RCD's so although the RCD is rated at 30 mA it is designed to trip some where between 15 mA and 30 mA, so with a 9 mA leakage which is the limit before we should split into more circuits, in real terms looking at a 6 mA leeway.

Before getting my new meter I could not measure 6 mA. And I would suspect many electricians don't actually test the mA leakage, yes they check the insulation resistance, but that is tested with DC, so any leakage due to capacitive or inductive leaking will not show up.

Had he not had the boiler checked many times, I would be looking at the pump, as I know my pump does not run when doing DHW, and likely with combi it runs at a reduced speed, but since tested many times one would hope they would have found that.

So some thing which only happens when the pipes are hot, points to some thing which only shorts when the pipes have expanded, I had a fault with daughters house where a socket screw only touched a neutral cable when one floor board was stood on, these types of fault are hard to find.

However from what I understand neither a insulation tester or clamp on or a RCD tester

have been used, so it may be some thing simple, the clamp on £35 and insulation tester £35 one would have expected the boiler man to have, but the RCD tester £150 one can under stand why not in his tool kit.

The electrician is required to have the installation tester and RCD tester to fill in his forms, but there is for some unknown reason not requirement to record the back ground leakage, so the clamp on to measure 0.001 amp even the electrician may not have, and same goes for measuring DC leakage amps.