Alpha combi tripping rcbo

[Rocboni]

Having a few issues with our alpha boiler 4years old, had a bit of bother with it last year in the back end towards summer, no issues over summer months, now the cold weather has started, its started tripping again. Then again no heating has been on over the summer!

Recent consumer unit change, from old dorman smith series 17 with dual RCD, never had any issues with it tripping those.

The boiler is virtually right next to the consumer unit,16A rcbo 2.5mm twin and earth down the back of the wall behind C/U under the floor and back up clipped direct into a FCU, flex out to boiler, 3 amp fuse. Cable insulation test is clear.

Controls are wireless so no faults with control wiring.

The boiler does not drip when firing up, having a shower ect, we usually just go to the tap and have no hot water, to find RCD tripped.

Has anyone had similar issues, read a few post regarding condensation dripping into flue stat?

Thanks

 

[Leesparkykent]

Sounds like a bit a pain in the arse, I wouldn't fancy paying a plumber £££ to poke around aimlessly in the boiler. Does the installation method/location of the boiler require it to be RCD protected?

 

[Rocboni]

Hi, no I'm not getting a plumber involved! I'd rather delv into it myself to have a look

Because the cable passes within the wall cavity and under the floor, then I would say yes it does have to be RCD protected, but I am thinking on putting it on a 16A mcb off the main switch (high integrity consumer unit) as I don't fancy waking up to run down the stairs starkers and flick the switch back on because I'm freezing my b***s off!

 

[Leesparkykent]

Could you pull In a bit of bs8436 cable using the old then no need for the rcd protection? That's assuming the cables are less than 50mm from the surface. In an ideal world you would find out why its happening but sometimes you've just got to do what you can

 

[Rocboni]

I could just clip a bit of 6242Y completely surface, as both cu and boiler are under the stairs (I know not ideal but "aye been") and take it off RCD, but as you say would like to know why it's happening.

Why would it not do it with the old dorman smith, rcd not as sensitive (no testing was done on the old RCds)

 

[ruston]

It may be the pump or a zone valve as it seems to be triggered by the heating.
If you can test the cables it may help .
Water and RCDs don't mix well lol. Worse with a bit of heat to help it on it's way.

 

[Rocboni]

Am I not right in saying with a combi hearing and hot water is the "same components" or no pump when it is just hot water? Won't be any zone valves?

 

[ruston]

Depends how you heating is configured . If your heating is zoned it will have diverter valves.
Hot water is heated on demand , as you say.

 

[westward10]

Does it trip when the heating kicks in.

 

[Rocboni]

We never "catch it tripping" i.e. We can't make it do it, we just go to wash the dishes (or mum does) and there's no hot water.

 

[ruston]

And it is only when the heating is on ? Is the boiler on it's own circuit, likely if it is right next to the board.What else have you not used over the summer ?

 

[Rocboni]

Like I say, we can happily use the heating and hot water at the moment but it seems to be tripping more randomly in the last month, it has got colder and the heating has been switched on so either one has triggered it, but the heating does work most of the time without it tripping and does not happen immediately

Boiler is on its own dedicated RCBO

 

[ruston]

Ok , I just wondered why it is on a 16amp breaker /rcbo.
Are you sure nothing else is fed from the 2.5 under the floorboards?

 

[Pat H]

May rig a temp light off that same supply so you can see when it trips!

 

[Rocboni]

No, it's only feeding that, it was always on a 16A so remained on a 16A/2.5,


I was just thinking of rigging up a relay with buzzer on the N/C contacts so it came on when the rcd tripped, but put of by the idea of getting woken up late at night!

 

[Rocboni]

No, it's only feeding that, it was always on a 16A so remained on a 16A/2.5,


I was just thinking of rigging up a relay with buzzer on the N/C contacts so it came on when the rcd tripped, but put of by the idea of getting woken up late at night!

 

[Pat H]

Use the relay trigger to reset the RCD

 

[Pat H]

Use the relay trigger to reset the RCD

 

[Last plumber]

Have you tried linking out the room stat for a day ?
Just to eliminate that. I know you said it's RF but the sender unit is wired into boiler.
( depends on make whether this can cause it but there is nothing I can think of at the mo, if you've no MV's)

 

[Pat H]

What type RCD? Type B maybe a Type C would help. Has pump motor got capacitor over it? Could be that.
Maybe worth a PAT test of the earth leakage of the feed into the boiler.