No Hot Water - Radiators are fine

[tonyhl]

Hi

Our system has started playing up with no hot water even though the radiators are all fine.

We have Potterton boiler with a fully pumped system with a 3way motorised valve and the usual tanks in the loft. Having done some searching on here my first thought was it's the motorised valve that's stuck. We have had it replaced some years ago.

BUT...

WIth the controls set to HW only all the radiators are hot. the pipe from the 3-way valve into the cylinder is hot (as is the one for the heating) which suggests it's going into the tank so why is it not heating it up.

Furthermore if I turn down the thermostat on the tank I can hear the valve motor kicking in.

So is it really the motorise valve?

Many thanks for any help you can offer.

 

[Agile]

Sludged up hot water heating circuit?

Air in cylinder heating coil?

Failing or blocked pump?

Tony

 

[tonyhl]

Sludged up hot water heating circuit?
System has never been flushed so this is a possibility. How would I deal with this - simply add something to the system and then refill it?

Air in cylinder heating coil?
Is there anyway to vent this off if it were air?

Failing or blocked pump?
I don't think it's the pump as all the radiators are getting hot across the whole house.

Thanks for the suggestions Tony

 

[jackthom]

There's something wrong with the valve or the wiring to it if the radiators are getting hot when only DHW is selected.

If you can check the voltage on the valves white wire it should only be LIVE when CH is ON.
With DHW only, it should be closer to zero volts and the valve should fall back to its "powered off" position where the CH circuit is shut off.

 

[EliteHeat]

Some cylinders were piped with 15mm on the return side, making them very susceptible to becoming completely blocked.

But it would be easy enough to drain down and work out what the exact problem is.

 

[tonyhl]

All fine now - needed a new Motorized valve motor and a load of air removing from the system

Many thanks for the suggestions