RCD tripped by central heating which is on a separate circuit

[L.F.]

My central heating is on a dedicated RCBO. The house has two other RCDs, one including the fridge, freezer and cooker. The other RCD is tripping virtually every day after the central heating has been on for 40 minutes or so. It will then often trip again after a few minutes. It can be reset and then it won't trip again until the next day. However, if I let the house temperature drop it will trip again once the central heating has been on for 40 minutes or so. It doesn't trip in the summer. It's driving me mad. Any ideas please?

 

[telectrix]

wild gues. could be cable/s (maybe with damaged insuluation) touching a hot pipe. when the pipe heats up from the c/h, the fault appears

 

[L.F.]

wild gues. could be cable/s (maybe with damaged insuluation) touching a hot pipe. when the pipe heats up from the c/h, the fault appears

Thanks, that has been suggested before. It does seem to be linked to heating the house from a lower overnight temperature as it doesn't trip when the heating periodically comes on to top up the temperature again during the day.

The following items are on the affected RCD circuit - TV, Sky box, hi-fi, various floor lamps, phone, alarm, shredder, laptop (when charging), phone booster, outside light, PC, printer, router, radio. It doesn't trip if I disconnect all of them (which perhaps suggests that it isn't caused by a cable touching a hot pipe), but I can't identify which, if any, item is causing the problem. Any combination of items connected results in a trip.

 

[telectrix]

with all the rain recently, water in outside light (or junction box/es) is a prime suspect

 

[Wilko]

Hi - you mentioned that it doesn’t trip in summer ... does that mean you had the same issue last winter, but it didn’t happen last last summer. Or does it mean this is a new problem that has just started to happen?
Also, how is your hot water heated please?

 

[Ned Gibbons]

Have you checked that the RCBO is connected directly to the main switch and not via RCD.

 

[radiohead]

Without any testing being carried out it's a guessing game.

 

[Lucien Nunes]

Thermal movement causing the fault to come and go is not contrary to your observation that unplugging the loads stops the tripping, if it is a neutral-earth fault. These often manifest as circuits that only trip under load, even when the loads themselves are not faulty. N-E faults can be influenced by loads on other circuits, so the time of day and season might affect the tripping threshold if circuits on the other RCD are more heavily used at certain times. However, it will always be the RCD that protects the faulty circuit that trips.

 

[Markyd]

can we get a pic of the consumer unit

 

[Dabbers]

ok firstly is this a combi boiler or a system boiler? have you got a big green water tank or white one? if you turn you hot tap on does the boiler fire up and give you hot water?, do you have solar panels and a Immersun?

 

[L.F.]

with all the rain recently, water in outside light (or junction box/es) is a prime suspect

Thanks for your suggestion. However, the fault has existed for two years, but it's getting worse.

 

[freddo]

Best call an electrician, likely quite quick to locate the problem with an insulation resistance tester.

 

[L.F.]

Hi - you mentioned that it doesn’t trip in summer ... does that mean you had the same issue last winter, but it didn’t happen last last summer. Or does it mean this is a new problem that has just started to happen?
Also, how is your hot water heated please?

The problem was there last winter too, although not as bad. No problems over the summer until we turned on the c/h.

ok firstly is this a combi boiler or a system boiler? have you got a big green water tank or white one? if you turn you hot tap on does the boiler fire up and give you hot water?, do you have solar panels and a Immersun?

We have an oil-fired Worcester Greenstar Camray condensing boiler. It is a fully pumped system with two motorised valves, one to the rads and the other to the coil in the h/w cylinder. In the summer we use the immersion heater, and turn off the boiler. We have PV panels and they help heat the hot water via an iBoost unit which diverts power to the immersion heater if we're not using the all electricity being generated.

 

[L.F.]

Best call an electrician, likely quite quick to locate the problem with an insulation resistance tester.

I have and he's done extensive tests. The problem is that it's intermittant.

 

[freddo]

Oh whoops, I missed that.

 

[Wilko]

Hi - if I’ve understood correctly, the problem ONLY happens when the boiler runs (?) as you've mentioned an immersion is used in summer to heat the HW. If so, then I’m thinking it might be worth insulation resistance testing the circulating pump.

 

[Ian Mills]

I had a customer with same problem the electric would trip but when I got there problem had gone, turned out to be a pipe and cable passing through same hole and the cable had the insulation strip off it as it had been put in, would only show fault when pipes where expanding when up to temp would be okay

 

[HappyHippyDad]

I have and he's done extensive tests. The problem is that it's intermittant.

An intermittent fault can be a right pain to track down. The electrician you hired may have been good at fault finding or may not. How long roughly did they spend with you? Could you state some of the actual results they found? It would help immensely if you had insulation resistance results for each circuit, otherwise I think it's unlikely anyone is going to be able to diagnose your fault on line.

 

[radiohead]

An intermittent fault can be a right pain to track down. The electrician you hired may have been good at fault finding or may not. How long roughly did they spend with you? Could you state some of the actual results they found? It would help immensely if you had insulation resistance results for each circuit, otherwise I think it's unlikely anyone is going to be able to diagnose your fault on line.

Agree, without knowing what the original electrician found or tested and his/her experience in the art of fault finding it's just guessing. I would ask a second electrician to take a look. To me this sounds like a simple N-E fault somewhere on the installation. Of course there is every chance it may be more complicated as well.

 

[Dabbers]

The problem was there last winter too, although not as bad. No problems over the summer until we turned on the c/h.





We have an oil-fired Worcester Greenstar Camray condensing boiler. It is a fully pumped system with two motorised valves, one to the rads and the other to the coil in the h/w cylinder. In the summer we use the immersion heater, and turn off the boiler. We have PV panels and they help heat the hot water via an iBoost unit which diverts power to the immersion heater if we're not using the all electricity being generated.

Have you tried running hotwater only without the central heating on and if so does the fault occur then?
[automerge]1582010304[/automerge]
Ok so i have been pondering over this and one thing that springs to mind is " where is the NEUTRAL connected from the rcbo " the FLy lead from the RCBO is it connected into one of the neutral bars that the affected RCD is into if this is the case then this will happen as the RCD is seeing an imbalance.. if you look closely at the picture the fly lead should be over on the far right hand neutral bar and the RCBO should be installed right next to the main isolator switch and the bus bar should be connected directly to the main incoming switch if it is not then this is more than likely your fault.
if your fuse board is not as described please send a pic!