Central heating pump red hot...

[paspatout]

Just walked in from work to a cold flat. The central heating hasn't come on at the time set. Nothing happens at all when I try to turn it on manually. Boiler is firing up for hot water though. I just touched the pump casing just now and it's so hot that I burnt my finger tip. Is this the sign of a stuck pump which has been trying to spin?

I have Saunier Duval Thelia Combination boiler.
Thanks

 

[JPC]

sounds like its running dry ?...is their water in the system ?

 

[Diyisfun]

I think it is if the pumps not running, could be stuck or system full off air

 

[JohnD]

turn it off

then try bleeding the highest radiator in the house. Does water squirt out forcefully?

If no, you are short of water.

If yes, find a large and a medium screwdriver, take out the large screw from the middle of the pump (a few drops of water may come out). Look into the hole with a torch and you will see the end of the motor spindle. See if you can turn it with the medium screwdriver. If no, pump is jammed.

What colour water do you get when you bleed rad?

What pressure is the boiler?

Do you know how to use the filling loop?

 

[paspatout]

Have opened each rad in turn and there's water bleeding out from each, no air. Just took the screw cap off the front of the pump to turn the spindle and it feel gritty when turned.

About two weeks ago I put system descaler in. Instructions said to leave in for three weeks. Could this be related, scale loosened up and now causing pump to jam?

 

[Diyisfun]

Yes..Can you free the pump to run?

 

[JohnD]

it's possible. what sort of chemical?

you could try draining and flushing the system and see if you can get the pump spinning after refill. if it feels gritty you will probably end up needing a new pump.

 

[paspatout]

The chemical was Kilrock system cleanser. Turning the spindle has free'd it so it's now firing up the heating but it sounds harsh and noisy.
Will try flushing it through a few times and see how it goes.