Heatslave 20/25 oil combi boiler pump issue

[Lisa17]

hi, the heatslave boiler is firing up but no hot water getting to the rads. We've change the water pump but that hasn't solved the problem. It appears there is no power getting to the pump. Any ideas?

 

[Terrywookfit]

Is the hot water heating ok.

 

[Lisa17]

Yes but the thermostat isn't cutting in so the water just keeps heating continuously and the water pressure is building up when the boiler is on.

 

[Terrywookfit]

Which thermostat is not cutting in ?
The pressure gauge should rise when boiler is on.

 

[oilboffin]

Which heatslave is it

 

[Lisa17]

Terywookfit -the hot water thermostat on the boiler(?) Excuse my ignorance

 

[Lisa17]

Oilboffin -worcester Bosch heatslave 20/25 oil combi

 

[oilboffin]

Check the actuator on the three port valve is working if it's not check the flow switch it could be stuck on and if it is the boiler will stay in hot water mode.Bob

 

[oilboffin]

Move the black lever over to the left the pump should start if not the micro switch in the actuator could be goosed may need new actuator.Bob

 

[Lisa17]

Thanks Bob

 

[Lisa17]

Oil boffin - just tried that and the boiler stayed on for much longer before switching off but alas did not deliver to rads. Thanks for all your help

 

[oilhead]

What is the water pressure reading? If it is low, the pump will have no head to pump.Which diverter valve does it have? Sounds very much like a diverter valve problem, which may need a new actuator, or just a synchron motor. Can you give us the numbers off the valve?

 

[oilboffin]

Undo the big chrome screw in the middle of the ch pump it may have an air lock wait till a bit of water dribbles out then tighten up.Bob

 

[snb]

This one normally has the Honeywell diverter. Take off the diverter head ( press in little metal button and rotate anti Clockwise)push down the divertor . These do get stiff with age. Often best to replace. )