Central heating/hot water pump problem.

[BigAl]

Hi there, I decided last night to check my heating system before it gets too cold, and unfortunately I have encountered a problem.
I have 4 radiators heating my flat and have a Grundfos selectric 4, Type 450 - 130 pump, probably 30 years old, the problem I have is that it isn't pumping.
I have checked the rotor and it is free and the motorised valves are operating.
When I turn on the central heating and hot water switches the motorised valves operates but the pump doesn't operate. I have removed the cover on the pump and checked for a power supply, the power is present, but when I turn off the central heating control switch the motorised valve shuts down the power stays on at the pump, the same applies to the hot water switch. If I turn the mains swicth off and on again the power to the pump has gone. when I operate the motorised valve switch and it opens fully the power comes on at the pump, but when I turn it off the valve closes but the power stays at the pump, and the pump is rather hot. Is this a symptom of pump failure. If so can you recommend a replacement type?
Many thanks

 

[aggis]

If you've got 240v to the pump [ live - neutral] & the rotor's not spining ypu need a new pump.
A grundfos ups 15-50 should do, or a similar 5 metre head pump.
Regards the power to the pump after valves shut, it'll be the pump overrun.
Makesure you turn off the electrics off & remove fuse at the fuse spur before changing it.

 

[BigAl]

Cheers aggis, I have replaced the pump but before I run the system I was wondering... when bleeding the radiators do you do it with the pump on or off?

 

[dontknowitall]

On ... or off!!

Best with it off though, until you think they're all bled. Sometimes the pump is needed to push some air around to an upstairs radiator.

 

[BigAl]

OK will give it a go

 

[BigAl]

OK pump working fine radiators all piping hot, but.......When I turn on the central heating switch the motorised valves operates and after the time delay the pump fires up no problem there, but when I turn the central heating switch off the pump keeps running. (Probably why the original pump packed in)? I have to turn it off at the mains switch, but if I turn the mains switch on again (without the central heating switch) the pump runs for approx 5 seconds and shuts off. This happens with either hot water or heating. I have checked the same system next door and as soon as you turn off the heating or water the pump stops immediately.
Any ideas on this issue

 

[doitmyself]

Which boiler do you have - make and exact model?

 

[BigAl]

Potterton Suprima 50L

 

[ferret]

Hi al , the suprima controls the pump and it is pump overrun you are experiencing , this is correct and should run for about 5 mins to clear residual heat to protect the boiler

 

[BigAl]

Brilliant thanks ferret, that has saved a pensioner an expensive callout. I never realised there were so many helpfull people out there. Once again thanks to all who helped, magic site.