Potterton Prima F ch only works when hot water required

[flinty]

My neighbour has a Potterton Prima F boiler (not combi) the problem is that they can only get the central heating on when the water in the cylinder requires heating. If you run hot water off or turn the thermostat up then the pump and boiler will kick in and all is well. But as soon as the demand for hot water is satisfied then the pump and boiler shuts down and no central heating even though the required room temp has not been reached.

Could it be that the three port valve is faulty or could it be the PCB in the boiler?

 

[waterworks]

Probably sychron motor in 3 port valve, check if valve opens when calling for heat.

 

[flinty]

When there is a call for heat from the ch only then nothing happens.

Only time everything works is when the hot water is calling for heat, then both ch and h/w work.

 

[AshaDPlumber]

Buy a new valve head, matcning the one you have. Changing the syncronus motor is a bit fidely if you have never done it before.

 

[waterworks]

If you have a Honeywell 3 port valve this opens for mid position and heat only by the sychron motor to work micro switch, the valve doesn't do anything for hot water thats why it works for hot water but not for heating SYCHRON MOTOR i think you find.

 

[AshaDPlumber]

Fair enough, but do you not find for the sake of taking the valve head off to change the sync motor you just aswell change the whole head.

Not arguing just give my 2 cents

 

[flinty]

Its LANDIS & STAEFA valve but I guess a new 3 port valve is required then.

 

[AshaDPlumber]

you should'nt have to change the body of the valve, a lot of effort. Just try to get a new motorised head for it. If not then sync motor, if not then whole valve