Boiler Trips RCD???

Gorie

Hello

I am hoping for some electrical / boiler advice.

I have a four year old house and in it lives a boiler made by Alpha (HE CB 25), it is a combination condensing boiler and is also around four years old. When it gets cold outside the boiler trips my RCD. This evening is the first time it has happened and as luck would have it I was home alone, in the shower, covered in soap and had to rinse with a kettle and a jug.

When the temperature drops, after around 30 minutes of normal operation, my boiler trips the RCD on my fuse board. If I reset the RCD and leave either the heating or hot water on it trips again after 30 seconds to 1 minute. However if I reset the RCD and turn the boiler off – no problems, moreover if I turn the boiler back on after around 30 minutes it works fine. The problem is intermittent and does not happen every time it gets cold. So around 8 months per year it works perfectly. Tonight it was 4 degrees outside so not cold enough to freeze.

Late last winter I had Br Gas out in March, they ‘serviced’ and inspected the boiler, told me it seemed fine, took £80 and told me to call them if the problem re-occurred. I then had an electrician out who tested my electricity for earth leaks and said that the board was fine also. I didn’t pursue it as everything worked perfectly until this evening.

The boiler sits in a utility room at the side of my house that can only be accessed from the outside. The room is brick built, completely dry and insulated but has no heating (except the boiler and pipes). I went outside this evening once dry and the condensing tube was not frozen - it wasn't freezing. The boiler has operated normally with both heating and water for the past month.

Has anyone any idea what is causing this intermittent fault? Why does it only happen after 30 minutes and why if I leave it does it then work perfectly? Its really annoying as whenever anyone comes to look at it, it works!

I'm thinking of calling BG again tomorrow but I don't want to be charged for a call out and told its fine.

Many thanks for any advice.

macman

Faulty RCD module? But that would not explain why it's always the boiler. Does the MCB on the boiler circuit also trip-if so change the MCB?

Gorie

Many thanks for your suggestion.

I have had the RCD tested on the sockets spur (which the boiler is on) and it works well. As the boiler has worked well for 8 months I don't think it is the circuit board there (unless cold might affect it). I am certain it is related to the cold weather outside, but whatever I google it says frozen condensate pipe - I am 99.9% certain that last night it wasn't frozen as I dried and went out to check.

Thanks Again.

nicka99

We have a similar problem with our outside lights.
Sometime, but not all, when the lights come on (PIR sensor), the RCD trips. When the moisture content of the ground is high (recently raining) then it trips. When it's been dry for a while then it doesn't.
Sparky thinks that the underground cable was damaged during recent building works (water main upgrade) so that a small part of it might be exposed to the ground. When ground is saturated then more current flows into it and trips the RCD. Only solution is to dig up the block paving to replace the cable but cost is prohibitive so we only use the wall lights by the house now !
Sounds like something similar - exposed cable somewhere reacting to environmental conditions ?

Gorie

Thanks for all the useful replies! Here is an update and, hopefully, the solution.

I called in British Gas (fixed price repair job) as in my experience they are better for such ‘non straightforward’ problems. After a call to Alpha, then another to an Alpha engineer, then a final call to a further engineer a theory was formed.

Apparently most combination boilers require that the flue be angled slightly upward or horizontal, however for Alpha boilers it is recommended that the flue be angled slightly down. When my boiler was installed the flue was angled slightly up. This can cause condensation to form on cold days and drip down back into the boiler onto a thermostat (flue stat) – causing the RCD to trip after a period of operation. After being turned off a while, when any water had evaporated, it would work fine.

The engineer opened the boiler and removed the heat exchanger and combustion chamber to access the flue and thermostat. There were signs of water presence where water would leak if dripping from the flue.

Three days later (after parts ordered) the heat exchanger (had sludge in it – engineer said this was probably unrelated) and thermostat (that showed signs of water damage) were replaced and the flue was removed and adjusted to angle slightly downwards.

It is early days and this is an intermittent fault so I will post again if the problem re-occurs, however this morning it was freezing and I did not experience the problem.

Hope this helps and if anyone wants the engineer’s details or any more info drop me a message, quite comically I was given a voucher for £25 off a further fixed price repair with British Gas that I can transfer – maybe they saw something else about to break???

southcoastrgi

not quite correct, with all non condensing boilers (combi or normal) the flue should angle down slightly away from the boiler, with a more modern condensing boiler (combi or normal) the flue should angle up back towards the boiler to allow the condense to run back down the flue into the boiler, but i'm glad you got it fixed

rapidalec111

Gorie wrote: »

Thanks for all the useful replies! Here is an update and, hopefully, the solution.

I called in British Gas (fixed price repair job) as in my experience they are better for such ‘non straightforward’ problems. After a call to Alpha, then another to an Alpha engineer, then a final call to a further engineer a theory was formed.

Apparently most combination boilers require that the flue be angled slightly upward or horizontal, however for Alpha boilers it is recommended that the flue be angled slightly down. When my boiler was installed the flue was angled slightly up. This can cause condensation to form on cold days and drip down back into the boiler onto a thermostat (flue stat) – causing the RCD to trip after a period of operation. After being turned off a while, when any water had evaporated, it would work fine.

The engineer opened the boiler and removed the heat exchanger and combustion chamber to access the flue and thermostat. There were signs of water presence where water would leak if dripping from the flue.

Three days later (after parts ordered) the heat exchanger (had sludge in it – engineer said this was probably unrelated) and thermostat (that showed signs of water damage) were replaced and the flue was removed and adjusted to angle slightly downwards.

It is early days and this is an intermittent fault so I will post again if the problem re-occurs, however this morning it was freezing and I did not experience the problem.

Hope this helps and if anyone wants the engineer’s details or any more info drop me a message, quite comically I was given a voucher for £25 off a further fixed price repair with British Gas that I can transfer – maybe they saw something else about to break???

Just wondered if the problem is still fixed - I have had RCD tripping with the same boiler for over a year - finally 100% certain it is the combi-boiler. The gas engineer needs help and I cannot convince him that the flu may be angled incorrectly.

lostpistonheadsprophet

Hi,

I was wondering how much BG charged you for the fixed cost repair?

Regards,


LP