Potterton Boiler/Controller problem

[jezzer99]

My CH has been switched off for a few months. Its a standard gravity fed system with Potterton Netaheat with separately controlled CH and HW.

Now when I turn on CH at the controller, absolutely nothing happens, but when I turn on HW, boiler/pump all starts up and works normally. I even can get the rads hot by switching the 3-way valve manually.

I'm thinking the controller is at fault. Has anyone got any suggestions what might be causing this behaviour?

Thanks

 

[namsag]

When heating is demanded it powers a motor in the 3 port valve, if it is not motoring over then 90% of the time a new motor will cure it occasionally it is the little circuit board in the valve that has gone an whole valve or head of valve will need replacing depending on make an model

 

[jezzer99]

My problem is that, when I switch on CH only, nothing happens at all. The boiler doesn't startup, neither does the pump start running.

Only when I switch on HW does everything burst into life.

That can't be the valve, can it ??

 

[namsag]

YES the valve does not require the motor to move to the position for HW

 

[jezzer99]

If I understand you correctly, you're saying that the boiler does not start up because the valve is not working correctly.

What stops the boiler coming on. Is there some feedback signal from the valve ?? In the past when I have had valve problems, the boiler works - I just don't get hot rads.

 

[simond]

Its because the valve defaults to HW on. Being a 3 port it does not have an 'off' position.

The (typically) orange wire on the valve is the feedback signal you refer to.

If the CH does not come on and the valve does not motor across then you have either;
- a programmer
- room stat
- motor valve problem

With a diagram for the valve you can easily discount the first two with a multimeter. I'm sure Namsag is right.

 

[namsag]

Have a look for yourself at www.honeywell.com type in mid position in the search all honeywell box and Y plan pdf will come up..

Doesn`t matter if yours aint honeywell all mid positions work the same

 

[bengasman]

Maybe a dumb question, but have you checked the roomstat?