Central Heating Tripping Electric

[bcfcjwb1]

Hi,

My electrics tripped this morning. I have managed to narrow it down to the central heating circuit tripping the RCD.

I'm trying to identify what is causing the problem. I've looked at both motorised valves and they look fine although the microswitch on one is sticky and has been problematic at times.

I have an 16 year old Megaflow pressurised system - installed when the house was built. The boiler is an Ideal Classic - the only reference that I can find on it is FF260.

I have disconnected the pump and the Sunvic (not earthed) motorised valve and the problem still occurs. When the problem started this morning the pump would run for a while before the RCD tripped. It now trips as soon as I switch the central heating circuit on via a fused switch in the kitchen. I have not disconnected the other (earthed) motorised valve (ACL Drayton Lifestyle) as it's more difficult to get to.

I can turn the heating and hotwater off at the programmer and then turn the power back on and it still trips. I can also turn the boiler off using the switch under the flap and it still trips.

Can I discount any of the components as the problem by what I've done so far?

Is it possible that the earthed motorised valve is to blame? I'm suspicious the electric is tripping as soon as the pump is called.

Any help gratefully received.

Thanks

 

[AngelesPlumbing]

My guess is pump problem

 

[picasso]

If it trips with the heating and hot water on the programmer switched to off I would be looking at the programmer first.

 

[jeff the gasman]

Flue fan
Jeff

 

[ALCPlumbing]

Are there any visible signs of a leak?
My money would be on pump but could be any faulty component really.

 

[picasso]

The op reckons he has disconnected the pump and its still tripping thats why I thought it might be the programmer.

 

[CombustionGuy]

fan in boiler.

 

[picasso]

fan in boiler.

He has turned the boiler off and the heating and hot water at the programmer off and it still trips so how would fan cause this ?

 

[Phill Peck]

If it's tripping without demand from programmer then I must be something that has a permanent live.
Could be the other zone valve or as suggested the programmer.

Turn power off remove programmer from backplate. Stand clear and turn power back on

DO NOT TOUCH THE BACK PLATE WHILE THE POWER IS ON

 

[stardanny]

I would thought it might be PCB in boiler and pump overrun but after looking in manual, it does not have pump overrun fitted, just a switched live and neutral and earth.

Your best bet would to get an electrician in to do test.

Also check that your motorised valves are not leaking.

Could neutral to earth fault cause RCD to trip, I wonder?

Daniel.

 

[bcfcjwb1]

Apologies for the delayed reply - work got in the way of investigations!

Thanks for the help... so far!

I isolated the entire airing cupboard to exclude both motorised valves, cylinder thermostat & pump. I then excluded the programmer and digital thermostat.

I then moved on to the frost thermostat above the boiler and that was fine too!

After reading your replies regarding the boiler, I had a good look at the PCB. That looked fine, with no evidence of bad components. I then turned the circuit back on and it still tripped the RCD.

I then moved onto the fan assembly, again it looked fine - I was able to move the fins with no resistance at all. The fan was replaced a few years ago. It made an awful squeaky noise for a few days before failing. This did not trip the electrics though, the boiler would just not fire up.

I moved the fan about a bit and also noticed a blue and red rubber tube connected to the fan assembly. These tubes were connected, but not as well as I would have thought would be needed, so I took them off and connected them again. I assume the tubes are connected to some sort of pressure monitor? This was in the top right of the boiler and had a microswitch at the front of it.

Anyway after all this, I put it all back together and it now works!!!!

The question is, does this mean anything to anyone? What the hell have I done to fix the problem? Would the blue and red tubes connected to the pressure monitor(?) make the RCD trip? Could the fan be on the way out and can I check it more thoroughly?

Again, any help gratefully received!

 

[bcfcjwb1]

An update...

I called out a local plumber at the weekend to take a look at the boiler for me, as I didn't want to take any risks.

He checked the boiler out in great detail but could not repeat the fault, so gave it the OK. He told me that RCDs can sometimes do that without any reason - I was left concerned by this.

The RCD has tripped again tonight!!

Having just had another look at the boiler, I 'wiggled' the 2 contacts going into the fan and powered back up and it's now working again.

Can someone tell me if the contacts could cause the RCD to trip or am I barking up the wrong tree - do I need to get another plumber out?

Thanks again.

 

[andymartin86]

If it is your RCD tripping its caused by an imbalance of current in the neutral and live conductors. This isnt caused by an overload but usually current flowing to earth.
If you are competent with a multimeter you need to check all resistances to earth with the unit powered off.

 

[Crezzer]

Sounds like waters dripped onto something it shouldnt.

 

[trinto]

I used to work as a gas engineer, but im in a different trade now, I remember that this was a common problem on the ideal, the reason the main fuse blows is because something is shorting out, so the main fuse is doing its job, ideal will be able to tell you what it is, I seem to remember it is the pressure switch, on the bottom right hand side of the boiler, water used to get behind them and cause a short, not a big job, as I say, try phoning ideal first,