Pump runs but no hot water unless room thermostat is on

[uncleshark]

Woke up this morning to find no hot water. The water pump is running but boiler not fired up....
Turn on the room thermostat and the boiler fires up. All radiator valves are off, as it is the summer, so no real hardship there.
Looked through the forums and it seems to be the diverter valve. Does this sound correct? Does the powerhead of the diverter valve tell the boiler to fire or is there another problem?

Mant thanks

Boiler: Appollo (Not sure what model, think its a 30/50)
Honeywell controller
Grundfos water pump
Honeywell diverter valve

 

[ChrisR]

If it's a 3 port valve, the cylinder stat brings the boiler on. If the water's cold though I don't see why the pump's on by itself.


See
http://content.honeywell.com/uk/homes/Catalogue/Sundial Plans/3.4 Y Plan.pdf

 

[uncleshark]

Any ideas???

 

[ChrisR]

Sure - check the wiring!