Pump only works on #2 or #3, #1 with some persuasion

[AndyJ]

Hi all,
For the past two or three days I've noticed that or CH pump is failing to turn when on #1 speed. Either tapping the unit, or moving the speed up to 2 or 3 makes the pump turn normally, but there's a lot of noise form the system (not the pump).

Can blockages in the system prevent the pump from turning on 1, but not on 2 or 3? That sounds like what's happening to me anyway.

I've lived in this house for 10 years and so far, this is the 4th pump we've had (5th if this one goes). CH engineers that we've had out say nothing wrong with the system - we're just having "bad luck". Surely not ????

Advise greatly appreciated.

 

[seco services]

sludge etc can put more strain on the pump and it will fail in the end.
do you have problems will certain rads not getting hot or only hot at the top ?
whats the condition of the water in the the small f/e tank in loft ?

 

[Deleted member 105431]

you need a new pump. Grundfos are the best.

 

[gas4you]

Agree with DM, but if your system water is black/brown thick and sludgy it will need cleaning. If not your new pump will probably fail prematurely

 

[simond]

Pumping against a blockage will kill them quickly.

It is possible the motorised valves are wired wrongly or you have TRVs on every radiator and no bypass for the water to get round when they are all shut.

Simple remedy is to take the TRV head off in the coldest room.

 

[ChrisR]

If they've been killed by pumping into a blocked circuit they overheat and then stop altogether. It wouldn't work on speed 2 but not 1.
You probably do have a sludgy system, and possibly a pump which tolerates that less well, such as a Wilo.
It would be worth some effort to get your system cleaner, though an all-day powerflush isn't the only option.
Grundfos pumps do put up with more dirt than some others.

 

[AndyJ]

Thanks all. Answered all my Q's