RCD 'C-Heating' tripping when turning heating on!!

[ben85]

Hello

Just to note about system: Traditional gravity fed indirect system with old ideal concord wrs240b boiler in 1st floor flat.

I was just settling down to a late film this evening and my central heating is timed to come on between 2am-6am

I heard it click on just after 2 as usual when in the front room, I then heard a loud click about 20 past 2, I wondered what the hell it was and then noticed the boiler had turned off, the pilot light was still on as is always even when c/h is not on.

I then noticed on the RCD box that the 'central heating' block as I call it had switched itself off. The lights & socket 'blocks' was still on as was the 'MAIN' switch but the 'central heating' block had switched itself off.

I then checked near the c/h pump in the cylinder cupboard and couldn't smell or see nothing different. I then went to the RCD box and turned the C/H 'mini-box' back to 'ON'.

I then turned to the main C/H switches and turned it on, this immediately tripped the 'C/H mini-block' in the RCD box.

So basically, the long and short of it all is, how do I narrow down which fuse, if any has tripped or what's causing the problem.

The boilers that old (but works fine & produces good heat) that it can't have many electronics, pump's being working fine. The system also has a 3port divert valve near the pump and I setted that to 'manual open' if it had got stuck and cause the switch to trip but as I mentioned earlier it tripped straight away.

Help me sort it out

Regards

BW

 

[jj4091]

It sounds like you are talking about your central heating system having a dedicated electrical supply & it is the mcb that is tripping. Does it do the same thing if it is set to hot water only? If it does I would think that you have a problem with the boiler rather than external accessories & you need to get someone to look at it. If you feel competant to do it yourself try posting in the plumbing/heating section with details of your boiler & someone may be able to give you more specific advice.

 

[Taylortwocities]

Many electrical faults like this that suddenly occur tend to be due to a water leak either in the pump or a valve.

Have a good look to see if there is some seepage, that is getting into the electrics, anywhere.

 

[1john]

i think it will be your pump, as mentioned, try on hot water only with the pump safely disconnected to eliminate.

 

[bongos]

i think it will be your pump, as mentioned, try on hot water only with the pump safely disconnected to eliminate.

Unless the HW is to temp then I thought that the pump would still be on circulating the water sround the cylinder's heat exchanger circuit for the HW system?

 

[ben85]

Hi, Right I've been up this morning trying to work out which part is at fault.

Following on from the comments I've read, I set the CH switch to Hot water only and turned off the pump and valve from the nearby switch and as soon as i switched on it tripped the 'central heating' mini-rcd box.

I did this with a combination of turning the boiler 'electrics' off and the pump/valve and it still trips the c/h mini box.

I also looked inside the 3 port valve and could not see any signs of leaking which would cause it to trip,

Is there a more thorough and systematic way I can go through to rule out certain things.

The actual central heating 'controller' is an old Randall 3020P with a mechanical timer at the top, 'timed, off and on switches to the left' and 'water only & c/h+hot water switches to the right'.

I've also looked at both the 3A fuses for the boiler power supply and the valve/pump but they both look fine, however, I don't know how to test for blown fuses.

Regards

BW

 

[bongos]

Following on from the comments I've read, I set the CH switch to Hot water only and turned off the pump and valve from the nearby switch and as soon as i switched on it tripped the 'central heating' mini-rcd box.

I did this with a combination of turning the boiler 'electrics' off and the pump/valve and it still trips the c/h mini box.

When you say its tripped "the c/h mini box" can you confirm exactly what it is that is tripping? Does it say something like "B6 MCB" or "30mA RCD"?

I'm guessing it's the MCB which is tripping which suggests a L/N fault somewhere. IS the boiler connected via a FCU or outlet? If so remove the fuse and confirm if you can now reset the MCB which keeps tripping (i'm assuming it's the MCB). If yes then you have a fault on the boiler side of the installation.

EDIT: Reading your post again it sounds like the "nearby switch" you refer to could indeed be a FCU.

I also looked inside the 3 port valve and could not see any signs of leaking which would cause it to trip,

Is there a more thorough and systematic way I can go through to rule out certain things.

The actual central heating 'controller' is an old Randall 3020P with a mechanical timer at the top, 'timed, off and on switches to the left' and 'water only & c/h+hot water switches to the right'.

I've also looked at both the 3A fuses for the boiler power supply and the valve/pump but they both look fine, however, I don't know how to test for blown fuses.

If the fuses had blown then the MCB would normally stay on but the boiler just wouldn't work. If you can't see any obvious leaks at the pump or the valve then you'll either have to disconnect each item separately until it stops tripping or call out a spark/plumber.

Make a note of exactly where how each item was wired before you disconnect it though.

 

[kevindgas]

get a connector block and put wires from pump in the block. switch system on if it doesn't trip the pump is the cause. simples!!

 

[ben85]

Hi

the Central heating Mini-box as I call is the central heating circuit in the RCD box I believe.

It's in the Kitchen and has a main switch and then 4 little switches for; cooker, sockets, central heating and lighting. When it trips the central heating 'little box' trips upwards to off, however the other mini boxes and the main switch stays on unaffected.

The central heating fuse has a 5A rating.

 

[ben85]

As regards the pump what would be a sure fire definite way to test if it was the pump.

Regarding the earlier from kevindgas the pump is connected to a little white box which also is connected to another with the connection to the 3 port valve.

The pump is a grundfos selectric, a few minutes ago i opened the little black cover on the top exposing the 3 wires (earth, live and neutral) where they go into the pump... Is the best way of testing if the pump is faulty is to disconnect one of them from the pump, which one is the best to do and then turn on and if it doesn't trip its the pump that is the problem.

Regards

BW

 

[ben85]

I've not got a connector block to hand, could i substitute this for something or work out if the pump is causing the trip another way?

 

[bongos]

the Central heating Mini-box as I call is the central heating circuit in the RCD box I believe.

The housing for all these switches is called a Consumer Unit and often incorporates an RCD as a safety device.

It's in the Kitchen and has a main switch and then 4 little switches for; cooker, sockets, central heating and lighting. When it trips the central heating 'little box' trips upwards to off, however the other mini boxes and the main switch stays on unaffected.

These are called MCB's and isolate individual circuits. The reason we needed you to clarify whether it was an RCD or MCB that was tripping is that they identify different faults.

If you're happy working in the boiler wiring centre then try kevindgas suggestion and report back.

 

[bongos]

The pump is a grundfos selectric, a few minutes ago i opened the little black cover on the top exposing the 3 wires (earth, live and neutral) where they go into the pump... Is the best way of testing if the pump is faulty is to disconnect one of them from the pump, which one is the best to do and then turn on and if it doesn't trip its the pump that is the problem.

Put the L/N/E into the terminal blocks and try switching the system on again. If the MCB trips with the pump disconnected then it's not the pump.

 

[ben85]

Right, I'm just going to buy a 'terminal block' from b & Q and will put the L/N/E wires currently going into the pump into the block itself and switch the system on, then if it trips it's not the pump. I'll just go to b& Q now before it closes and get one.

Let you know soon as

 

[bongos]

Sorry.

Choc blocks/terminal blocks/connector blocks all different names for the same thing.