I have a Baxi back boiler system and since the fault developed have replaced the old Tempus controller with a new Tempus 7 (backplate unchanged - wiring identical). HW is working fine, but there is no response at all from the system when I switch on the CH. The Drayton mid position actuator appears to be stuck in one position, the W/M/H label is missing, but I expect it is in W as it is being held by the return spring (and I have hot water). The manual lever moves freely and I have removed the actuator and can move the valve spindle easily, though only through a few degrees (looking at the limited range of travel on the actuator, it seems okay). I have removed the pump bleed screw and the pump also turns freely. I have also tried opening the mid position valve manually and holding open the manual lever on the actuator to coax a response, without luck. Any help would be much appreciated.
HW but no CH - Any help much appreciated
- Thread starter CJW
- Start date
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sounds to me like the fault I had with a mid position valve.
When I moved the valve manually to the CH position there should have been a voltage on the orange wire but there was not.
This was due to a faulty microswitch.
I believe this problem is always down to a 'stiffish valve spindle' or a 'faulty motor' or 'faulty microswitch'
A replacement actuator head takes care of the last 2.
There's one point I forgot. Make sure the room stat is supplying power to the white wire of the valve, when heat is called for.
When I moved the valve manually to the CH position there should have been a voltage on the orange wire but there was not.
This was due to a faulty microswitch.
I believe this problem is always down to a 'stiffish valve spindle' or a 'faulty motor' or 'faulty microswitch'
A replacement actuator head takes care of the last 2.
There's one point I forgot. Make sure the room stat is supplying power to the white wire of the valve, when heat is called for.
Thanks Mandate for excellent advice; there was no output on the white wire, as you said. I now have the boiler firing up, but it stops again straight away. It does stay on if I switch on the HW first (and the radiators get hot). Could this be the microswitch fault you mentioned? Thanks a lot, Carl.
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when on HW only the valve has no role. The feed to the boiler is direct from the cylinder stat, but there is a junction terminal that connects the orange wire of the valve into this feed to the boiler.
As soon as there is a demand for CH and HW the room stat powers up the valve through the white wire and sends it on its way till it stops at the mid point. Power to the boiler is still as before via the cylinder stat.
When HW is satisfied or you turn HW off and the demand is for CH only' power to the boiler from the cylinder stat is removed. The valve then moves on to the final position and through the second microswitch power to the boiler is restored by coming through the orange wire and joining up with the cylinder stat wire.
My valve was moving ok to the final position, but the orange wire had no voltage. Due to the time factor I changed the whole actuator head and later dismantled the faulty head to prove the microswitch was the problem. ( I now have spare head after delving into the microswitch and cleaning it up )
So no voltage on orange wire means faulty microswitch or motor not moved valve far enough.
As soon as there is a demand for CH and HW the room stat powers up the valve through the white wire and sends it on its way till it stops at the mid point. Power to the boiler is still as before via the cylinder stat.
When HW is satisfied or you turn HW off and the demand is for CH only' power to the boiler from the cylinder stat is removed. The valve then moves on to the final position and through the second microswitch power to the boiler is restored by coming through the orange wire and joining up with the cylinder stat wire.
My valve was moving ok to the final position, but the orange wire had no voltage. Due to the time factor I changed the whole actuator head and later dismantled the faulty head to prove the microswitch was the problem. ( I now have spare head after delving into the microswitch and cleaning it up )
So no voltage on orange wire means faulty microswitch or motor not moved valve far enough.
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