CH only works when HW valve comes on

Postby leon_funnell » Mon May 14, 2007 2:09 pm

I have a Potterton Prima 60F system with separate diverter valves for CH and HW. The valves appear to be moving fine, as I can see the little tab move when they open and close with room thermostat/timer/tank thermostat operation. The problem I have is that the CH valve doesnt seem to start the pump running. The pump only starts when the HW valve opens - eg timer on and HW thermostat below start temp. This also happens when I manually actuate the valves. If the CH valve is closed adn the HW valve is open, it heats the hot water. If the CH valve and HW vavle are both open, the HW and radiators both heat well.

The system provides good heat on all radiators top and bottom when I force it to run by turning the HW thermostat up, and the HW side works very well. :roll:

Any ideas? I am not an expert in CH systems, but I am very good at troubleshooting and very technically minded.
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Simply Build It

Postby Paul Pepper » Tue May 15, 2007 6:21 pm

Both valves should have a grey wire (permanent live) a brown wire (switched live) and an orange wire (switched out live). If the fault valve has power on both grey and brown, but none on orange then the internal microswitch on the valve has gone and needs changing! (you normally have to change the entire valve)

Paul Pepper
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