Cental Heating Boiler pump probs

[SmileySurf]

Hi all,

I'm having problems with my central heating boiler pump (Grundfos UPS 15-50x18). Sometimes it will run when the boiler fires up but stops after a few minutes even though the boiler is still lit (ie no overrun). The run time varies from 1-2mins to 11mins. Sometimes it won't run at all. When I removed the vent plug the pump shaft is free and small drips of water are clear. I've checked the voltage at the PCB and pump terminals and get 248V. Can't see any visual problems with the capacitor (no leaking or bulging) - don't have capacitance setting on my multimeter. Could this problem be the capacitor or something inside the pump?

Thanks in advance for any help.

 

[ScottishGasMan]

The pump should never stop while the boiler is in operation. Its not the capaciter as this is used primarily in starting the pump not keeping it going.

Have you confitmed the 248v at pump live/neutral when it has stopped? If so it would point to a faulty pump

 

[SmileySurf]

Thanks for the reply. Yes I know the pump shouldn't stop while the boiler is on. Seems to do different things on different days. I'm sure it was still getting 248V when it stopped. Today the pump won't start/run at all despite having 250V at the terminals - could this be capacitor? What should the resistance be across the pump terminals?

 

[ollski]

From memory speed 3 is roughly 200 ohms, but just fit a new pump head.

 

[SmileySurf]

Showing 0 ohms across terminals - that's not correct/good is it?

 

[simond]

Just buy a new pump.

Look at the PC number on the rating plate, the first two digits tell you how old it is.