No Hot Water, Faulty Motorised Valve?

[Longclough]

Boiler does not fire when the controller is demanding Hot water. Heating is working correctly, ie boiler fires on Stat demand.

Boiler is Potterton Suprima 40L, open vented system with 2x2 MV. The valve for hot water is a Honeywell valve. As the wiring centre is near to the valve I have tested the voltage on the wiring and found the following:

Valve Wire Colour --> connect to wire in wiring centre

Grey x2 (1 to CH and 1 to HW valve) --> Blue
Brown --> Yellow
Orange x 2 (1 to CH and 1 to HW valve) --> Red
Blue x3 (1 to CH, 1 to HW and 1 to pump) --> Blue

with the controller selected to on HW demand:

240 volts measured on Grey to Blue and Brown to Yellow

with the controller selected to on CH demand:
240 volts measured on grey to Blue, Brown to Yellow and orange to red

I can only assume the problem with the HW valve is it is not supplying 240 volts on orange and red. Can someone confirm that my diagnosis is correct and indicate the likely problem with the valve? Can it be fixed or will it need replacing?
Thanks is advance

 

[EFLImpudence]

Yes, it would appear your diagnosis is correct.

Does the valve move when it should?

Have you tried manually moving the valve?

It could be the motor, the micro-switch or the valve itself sticking.




What are you using to detect voltage?

 

[Longclough]

EFLImpudence thanks for your response.

I measure the voltage using a multimeter.

I am not sure the valve is moving as I can't hear it.

When I set it to manual nothing happens, unless the CH is calling for heat, then when I latch in Manual HW is heated.

I tried move the valve to manual a few times whilst the power was off. When the HW call came from the controller the valve seemed to work. However before the cycle had completed the valve was not doing anything even through there was a demand.

 

[EFLImpudence]

I measure the voltage using a multimeter.

Ok. That's good.

I am not sure the valve is moving as I can't hear it.
When I set it to manual nothing happens, unless the CH is calling for heat, then when I latch in Manual HW is heated.

So, as you say, the voltage is not going to the boiler.

I tried move the valve to manual a few times whilst the power was off. When the HW call came from the controller the valve seemed to work. However before the cycle had completed the valve was not doing anything even through there was a demand.

Sounds like it is the works of the valve that are faulty.


Are you comfortable taking off the cover and examine the switches?
Do it with the power off and use the meter to see if you get continuity between the grey and orange when you operate the valve manually.

Some valves allow the top to be replaced without draining.
If not you may as well replace the whole.

 

[Agile]

Being told the make of motor valve would get much more detailed and helpful answers!

Tony

 

[Longclough]

EFLImpudence, thanks for input, its much appreciated.

I am happy to take the cover off and perform the test you have suggested. Out of interest is this to test that the micro switch is operating correctly when the valve reaches the end stop (by manual selection)?

By works, I assume you mean the powerhead, which can be replaced without the need to replace the complete valve?

Tony, in my original post I mentioned that the valve is a Honeywell Valve. Not sure on the exact model, but it does have a Pip on the metal casing.