Central heating pump problem

[CASEL]

Please , can someone help me with this one

I installed my own CE system 27 years ago and has given me stirling service until very recently.

IE
Potterton Netaheat 10-16 boiler.
Fully pumped 2way valve system.
LANDIS & GYR RWB2 programmer.

I have recently noticed that the pump doesn't trip out when the CE/HW is programmed to go off and will continually run until I actually switch off the main electrical supply to the boiler !

1) I don't believe there is a pump over-run thermostat fitted to the 10-16 boiler which could have caused the problem.

2) I have actually unplugged the LANDIS &GYR programmer from it's mounting plate and still the pump runs !

3) Could it be the relay unit in the boiler that's gone US ?

4) Could it be a PCB problem within the boiler?

5) Or is it something daft I have overlooked !!

Otherwise the system still runs perfectly . Would appreciate any advice you can give me.

Regards colin

 

[ChrisR]

I put much the same in my kitchen in about 1982, and I can't remember exactly how I wired mine either! But if mine behaved as yours, I'd suspect a short in the pump wiring but it's hard to see how. It should be wired in parallel with the boiler.
You're right, 10-16 had no overrun.

 

[buck51]

could it be you have a zone valve stuck in the on position,

 

[namsag]

Providing it has not done it all the time buck is on the right track .
Check the microswitches in the motorised valve one of these could be stuck

 

[gas4you]

Some of these netaheats did have a basic thermostat pump over run, not many though.

Can't remember which ones though or how they are dentified other than looking at the boiler stat.

 

[twgas]

Some of these netaheats did have a basic thermostat pump over run, not many though.

16-22 had pump-overrun, not the 10-16 iirc

 

[CASEL]

Wow! Problem sorted guys

Many thanks to:-

ChrisR
buck51
namsag
gas4you
twogas

buck51 and namsag were correct, motorised valve on CE side had packed up.

Many thanks again for your prompt replies.

Regards

Colin