Grants combi boiler firing but no DHW or CH

[leila3719]

I really hope someone can help. My 8 yr old Grants combi boiler is firing when a tap is turned on and is getting hot to the touch when I open the top up but no hot water at all is coming out. The pipe feeding to the pump seems to be getting hot but the actual pump isn't.

Please help.

 

[chr15]

Are you sure its actually firing up and not just the fan you can hear running? Does it fire for central heating?

 

[leila3719]

It is definately firing for DHW but not for CH.

 

[gas4you]

Do you mean the hot taps run cold or don't run at all?

Could be the pump knackered if they run cold.

 

[AlanE]

when I open the top up but no hot water at all is coming out.

Open what? Automatic air valve? If so it is either siezed or there is no system pressure.

The pipe feeding to the pump seems to be getting hot but the actual pump isn't.

Air in system or pump defective.

What is the system pressure as the Grant combi is a sealed system boiler?

 

[leila3719]

When I open the outer casing and feel the actual boiler it is hot but when I run the tap it is cold water coming out.

The system pressure is correct - 1.5 bar. I thought it might be the pump, it there a way of proving that before i buy a new one (it was only replaced around a year ago)? The pump is a grundfos ups 15/50.

 

[outinthestix]

What happens when you run the tap ? Does the boiler fire up ? Does the pump run ? If neither of these it could be the flow switch, or diverter valve end switch (not sure which of these your boiler has).

 

[leila3719]

When the tap is run, the boiler fires. I don't know if the pump runs (how can I tell this?). It doesn't get hot which I think it previously did when everything was working fine. The funny thing is when I turn the heating on the boiler doesn't fire.

 

[Agile]

It certainly sounds as if the pump is not running.

See FAQ above top check if the rotor is turning and if not if its free to turn.

If free any not turning then check to see if 240vac applied when DHW is demanded.

Tony

 

[JPH/01]

I think the grant combi originaly came with a 6 meter head pump(15/60 UPS) . Ring grant uk ask for a list of approved engineers, this way you will get someone who knows what they are doing and will have the bits to fix it.
I agree it sounds like it may be the pump gone or not getting any power !.