Hot Water Cutting Out

[YorkyBar]

I have a Potterton Prima F 60 (not a combi boiler).

I have been using the hot water on a daily basis. I recently used the central heating and it works fine. At roughly the same time (coincidence?) the HW stopped working.

When I turn on the HW, the boiler fires up, the pump comes on and the HW motorized valve opens. It stays that way for a few minutes and then everything turns off. As far as I can tell the cylinder thermostat is working. It clicks at about the right temperature and (I think) sends the right signal back to the control panel.

I can force the HW on by turning on the CH and manually opening the HW valve.

Anything else I can check?

Thanks!

 

[dcawkwell]

Maybe your timer relay on the HW is faulty if everything is switching
off.

Switch off. Remove the cover of the timer and wire a live directly to
the HW live. Replace cover and switch on. The HW should now be on
all the time.
If this fixes it new timer required.

 

[YorkyBar]

That's a good point, thanks.
I will have a look tonight.

 

[YorkyBar]

The timer is electronic (Horstmann CentaurPlus) - and I think the cover is glued down so I couldn't open it! I reset the device to factory default but it didn't help. Do these electronic timers often fail?

I could check the Honeywell control board that the timer must be wired into, to check the signal it is sending.

 

[jackthom]

If you can identify the wire from the programmer on the connecting strip that would be a good idea. With two 2-port valves there's a fair chance the wiring will be something like the diagram at the end of this PDF.



http://www.google.co.uk/url?sa=t&rc...sg=AFQjCNGC-DtU-U965yvpSUJwZIQUtK73Zw&cad=rja

 

[YorkyBar]

Thanks for the link. The exact model is this one:

www.bssindustrial.co.uk/download/371/Wiring Centre.pdf

I checked the voltages with the HW on and when the HW had cut out.

The voltages on the cylinder stat and timer are the same before & after the HW cut out - so I think they are working correctly.

On the HW valve with HW on, Grey (perm. live), Brown and Orange are live.
On the HW valve with HW cut out, Grey (perm. live) and Brown are live.

I think the Orange goes live when the valve opens and tells the boiler to fire.

Does this suggest the valve motor is faulty? Or the the whole unit?

Thanks.

 

[YorkyBar]

Replaced the motorized valve (v4043h)and all is working now!