Potterton Netaheat Electronic - turns on and off by itself

[RobeK]

Hi I have a Potterton Netaheat electronic. Since replacing the pump earlier this month, we have found that the boiler will fire up of its own accord and run for a few minutes and then go off. It then turns back on ten or so minutes later.
This occurs outside of the timer settings.
I have tried different combinations of turning the room thermostat to nothing and turning off the time control and switching the boiler thermostat to the minimum. But it still fires on its own.
Anyone had this before?

 

[TCCHeating]

Do you have a motorised valve somewhere? Could be in airing cupboard, if you do, i supect it/they could be faulty

 

[ianmcd]

you have an external control fault probably a 3 way valve or one of 2 x 2 port valves more common with the 2 port valves to stick

 

[RobeK]

Do you have a motorised valve somewhere? Could be in airing cupboard, if you do, i supect it/they could be faulty

I don't think they are motorised. The 2 valves were replaced along with the pump earlier this month.

 

[RobeK]

you have an external control fault probably a 3 way valve or one of 2 x 2 port valves more common with the 2 port valves to stick

The two valves were replaced along with the pump earlier this month. The other concern I have is today the heating is now coming on. This seems to be an awful waste of energy and potentially unsafe?

 

[TCCHeating]

You may be thinking of the pump isolation valves there, in which case, they definately are not motorised!

Have a look for 1 or 2 rectangular boxes connected to the pipework with a wire coming from them.

 

[ianmcd]

That would more likely be the pump isolation valves and not the zone valves, what control can you have ? can you get HW on its own and CH on its own or does the HW come on automatically when you select CH ?

 

[RobeK]

You may be thinking of the pump isolation valves there, in which case, they definately are not motorised!

Have a look for 1 or 2 rectangular boxes connected to the pipework with a wire coming from them.

Yes there is silver box made by Honeywell which has an electrical cable running from it. It has a lever which on one side says AUTO and the other says MAN OPEN. The lever is nearer AUTO. The new pump has a running water sound coming from it. It is a Grundfos UPS2 15-50/60 and the LED is set to position 2.
See pics in my album

 

[RobeK]

That would more likely be the pump isolation valves and not the zone valves, what control can you have ? can you get HW on its own and CH on its own or does the HW come on automatically when you select CH ?

My timer only allow HW and CH on timer together or one of the other. They are not controlled independent via a timer.

 

[TCCHeating]

Have a look at post 17 in the faq. It Should help you

 

[ianmcd]

The silver Honeywell box as you call it sounds like a 2 port zone valve and it sounds as though the end switch is sticking , an easy repair for an experienced heating engineer, nothing to stop you legally from doing this yourself but can be out of a normal DIYrs scope

 

[TCCHeating]

Erm? The valve in the picture is a 3 port valve

 

[ianmcd]

never looked at the pics sorry just went by him having a gravity wiring set up thought he only had one valve

 

[ianmcd]

sorry OP as correctly pointed out you do indeed have a 3 port valve or Y plan try switching both CH and HW to the off position on your programmer then see what happens with the lever that is sitting a auto , see if it springs back or not , if it does not then its most likely you only need a synchron motor which you can buy for under £20

 

[RobeK]

Just thought I would update since it happened. Turned out to be a fault between the timer controller and the immersion tank thermostat. Both replaced and back to normal. Thank you for your input though.