RCD Tripping

[emgee]

We have a central heating system fired by a Potterton Neataheat Profile with Groundfus pump, Honeywell V4043 zone valves on heating and hotwater circuits,Landis & Gyr programmer and a Satchwell room stat.

When the boiler is switched off due to programme settings or temperture changes it (sometimes) causes the Protek RCD on the distribution board to trip shutting off all house power circuits.

Can you suggest the most likely cause of the problem? Could it be caused by a fault on other circuits than the heating? - I know there are some radial circuits with several sockets.

I think the problem only started after the old fuseboard was changed for the Protek.

 

[Steve]

Protek isn't a respected brand. Cheapest of cheap.

First thing is, did your previous fusebox have any RCD protection?

When was the fusebox changed?

Is your heating system also new?

 

[emgee]

Hi Steve,

Original board had no RCD and was changed about 5 years ago.

Boiler and controls installed 17 years ago,

 

[Paul Barker]

I can't get my head around why it should happen when the boiler is switched off.

You would expect it to trip when a new roblematic circuit is switched in.

In boilers with a pump overrun circuit that would only become active when the boiler is switched off.

It is normally 4043H used for s plan heating controls these are sprung into shut position and opened by 240v on brown leed. So again on taking away the demand for heat there is no new electrical activity, the valve springs shut.

If you had a mid position valve I would have suspected that as there are all sorts of things going on with those. They are held electrically in some positions depending what was happening when temperature of one circuit was satisfied.

The only circuit I can see which is activated on lack of demand is the pump overrun. I don't want to balme the pump (which is normally the culpret) because it would have been on already during a heating demand.

 

[emgee]

Thanks Steve


My wife has reminded me that it has occurred when the microwave has been switched on or items switched on on one of the radial circuits. - but these happen much less frequently than when the heating or water is switching off which is almost every time!

I hadn't appreciated the significance of the problem occurring on boiler swith-off (as opposed to switch-on) ! Good point.

 

[cheesepuff]

maybe the boilers on a ring circut and when the microwave or any other high power appliance is in it overloads and = welcome to tripland

 

[Steve]

maybe the boilers on a ring circut and when the microwave or any other high power appliance is in it overloads and = welcome to tripland

What???


RCDs can trip at strange times. They are very sensitive pieces of equipment. It would seem that since it happens when your boiler powers down, I'd look at the pump first, I'd expect these go faulty more than anything else on a basic heating system. Tracing faults like this can, unfortunately, be expensive and its a case of trial and error.

What you could do as a test is wire the pump up to a 3 pin plug, and plug it in. If, when you turn it off at the socket, it trips the RCD, you know its the pump. Dont try similar with the boiler - I have no idea how these work. I do know the pumps run on 240V and it does them no harm running cold. Whilstever the pump is disconnected from the controls, ensure the heating is off at the mains!

Also, while doing the test, turn off any unessecary appliances, as you are intentionally tripping the power, you dont want anything damaging.

 

[emgee]

Steve.

Thanks for taking the time and trouble to deal with my problem.
If I resolve it I'll let you know

Regards

Emgee

 

[emgee]

Steve

I finally got round to trying what you suggested with the direct supply to the pump.
After switching on and off eight times with no tripping I have to conclude it's not the pump. Could a faulty zone valve be the culprit? or do you have any other suggestions?

Emgee