Central Heating pump running SLOW ?

[6666]

Thanks for all the tips, etc. a couple of days later a plumber turned up and replaced the pump and 3 way valve (which was leaking) he kindly left me all the broken bits so I can have a look at the pump, check speed etc. New pump is Grunfoss !! Old was too.

I did mention the mounting the pump horizontally but there wan't "time" to do this, guess I will just have to do this myself.

 

[Gasguru]

Went to a job last week where the hor water was working OK but only the rads upstairs would heat up. Grundfoss pump had been set on 3 and even with upstairs rads turned off downstairs wouldn't heat up.

Changed the pump as the nose test on the wiring box indicated burning and everything now OK on speed 2.

Pumps can run slow (this one had a clean impeller and the bearings were fine).

 

[ChrisR]

Oooh that's an interesting one then, I'll get my anorak and come over for it...
Actually it is, because Grundfos don't go slow so often. Don't suppose you've got the kit to measure things??

Proctological - sorry a typo. A tongue in cheek( ) allegorical explanation..


(Proctology is one of those professions which you can claim to practise, when asked on holiday. It shuts people up. Tell them plumber and you never hear the last about their U bend)

 

[barjac]

Thanks guys.
I can confirm that the impeller can break loose on a Grundfoss pump.

I suddenly lost heating downstairs yesterday and was still getting reduced heating upstairs.
I can only assume that the upstairs was thermo-syphoning enough to circulate to some degree.

On removing the pump head the impeller was rotating free on the shaft. I chocked it parallel to the face of the motor with three one pound coins and ran warm Devcon fast setting epoxy around the centre. I would have preferred slow setting Araldite, but it's winter and her indoors wanted it back on fast!
It's back up and running fine for now - we will see how well the Devcon holds up.

Without this thread I would not have suspected the impeller - great site!