The pump has been 'jamming' for the central heating for a while, necessitating a good whack to get it started, although the hot water has been ok.

I knew that I could only be living on borrowed time, and today I seem to have lost the lot. No CH, and, as the day has gone on, no hot water, either.

There's lots of noise, but no action.

It's not that I'm too tight to pay for a new one, as I have already left a message for my wonderful ch engineer to please come out to replace it.

I just wondered what the cause might be, and if there's any self-help I can administer until he can call.

Linda T, March 2008

When you say turn off power is that just turn the boiler off or shut down electrics thanks so

Kevin, November 2016

I followed the advice and find that my Grundfos pump is running , seems that I need a new Capacitor. My pump is a Grundfos UPS 15 45 x18 . The original Capacitor is Bosch MKP 3uF +/-10 % b , 320V ~DB -25/85 *C . Measures Length 60 mm by Diameter 25 mm. I wonder what is the correct replacement capacitor from Maplin or other supplier ?

Brian, December 2013

took tractorgears advice , I checked when heating turned on there was 240v at supply in to valve ,that was ok then took out the big bleed screw and inserted a screwdriver in end of pump and span it to kickstart the pump, the pump worked so purchased a new capactitor number n39kg fitted it buy pushing in the two wires and them the heating pump worked fine

billiy, April 2013

Replacement capacitor available from Maplin, stock No. N39KG. This is a wire ended 2.5 microfarad 400 volt capacitor which is physically identical to original fitted by Grundfoss and has better voltage rating. Price is £3.09. Push fit wire leads into terminals 4&8. Tip: strip wire ends to same length as on original capacitor or they will not make proper contact.

Tactorgear, February 2013

If capacitor is suspected as being defective, to prove that this is the case, remove bleed screw insert small slotted screwdriver to spin impeller in direction of arrow while power is applied to pump. This action should "kick start" pump if pump motor windings are OK and pump is not seized. Pump will continue to run until power is removed BUT it will not restart when power is re-applied without a further kick start; this is what the starting capacitor does automatically when it functions correctly.

Tactorgear, February 2013

John from Malvern can you tell us who was the ebayer that sells refurbished Grundfos UPS pumps?

Many thanks

Richard, November 2012

Just had a similar problem and found a solution from an ebayer who sells refurbished UPS 15-60s for £35. I bought one off him anyway then swapped it over with the seized one. Dismantled the old one by undoing the four screws that hold it together tapped out the inner impellar assembly from the other side (you can unscrew the silver slotted disk and use a large screwdriver and small hammer and gentle taps). Then clean under running water turning the impeller back and forth to free it. Easy job. Nice one ebayer!

John from Malvern, November 2012

Greiga.......Great work. Checked all that has been advised in your blog and system is all working again. LEGEND.

Shaun, October 2012

...thanks to "greiga" for the tip (remember my Dad doing something like this when I was a wee kid), as it has just got my pump moving again.

sean, February 2011

You could remove venting cap and try turning with small screwdriver, if it rotates freely it may be that the start up capacitor is defective. observe correct position of the 2 wires, I think that it is terminals 4 and 8 this problem may be more noticable when things are hot.

Paul, December 2010

Thanks to griega! Your advice worked PERFECTLY & now I have central heating again & it didn't cost me a penny!

Phil

Phil T., December 2010

Before going for the pump first check the switch
to see if " central heating plus hot water " has been
selected .
A generic Grundfos manual is available from :
www.screwfix.com/sfd/i/cat/pdfs/01/p3983301.pdf .
With Grundfos UPS 15-50x18 there are no
isolating valves and access is via a central screw.
Putting a little "Fairy Liquid" or similar washing up
liquid into the hole softens the water and has a
beneficial lubricating effect , perhaps more so than
bashing the pump.

Philip, December 2009

1. turn off power
2. put plate or small bucket underneath
3. remove cap with large slotted screwdriver
4. steam and a little water will probably come out
5. wait a few mins
6. use small slotted screwdriver to rotate pump clockwise
7. do this for about 20 turns
8. power up
9 if it doesnt rotate on its own use screwdriver and it should kick start it

greiga, December 2008

the cause of a jamming pump is sludge or the bearing or it's just knackered

hi-spec plumbing & heating., March 2008