Problems with grundfos boiler pump

[Smiley]

[FONT=&quot]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. [/FONT]

 

[AWheating]

What boiler is it?

 

[oz-plumber]

Capacitor.

To check it, take the vent plug out and see how hard it is to stop the shaft with a screwdriver when the pump is running. If its easy, then its the capacitor - most of the time

 

[Smiley]

Boiler is a Potterton Suprima 50L and a Gledhill Boilermate 2000 thermal store - where the boiler pump is located.
Now the pump won't start/run at all despite having 250V at the terminals so unfortunately can't "see how hard it is to stop the shaft with a screwdriver while running" test. What other tests/checks can I do?

 

[plumben]

Should we be giving advise on repairs inside the boiler casing?

 

[gassafe]

Should we be giving advise on repairs inside the boiler casing?

Who said its inside the boiler?

 

[gassafe]

Capacitor.

To check it, take the vent plug out and see how hard it is to stop the shaft with a screwdriver when the pump is running. If its easy, then its the capacitor - most of the time

I thought the capacitor just jumped started the pump

 

[plumben]

Who said its inside the boiler?

*problem with grunfoss Boiler pump
*I've checked the voltage at the PCB and pump terminals and get 248V.

Just makes it slightly sound like it could be in the boiler, with the strict rules this forum seems to have about people working on gas or in boilers...

It might no be but just looks like it could be in the boiler to me

 

[gassafe]

Yeah maybe, but a lot of boilers feed the pumps power supply now too

 

[rpm]

I thought the capacitor just jumped started the pump

That's what I was taught.

 

[oz-plumber]

I thought the capacitor just jumped started the pump

There are 2 basic types of capacitors.

Start Capacitor - 130v to 330v
Run Capacitors - 370v to 450v

Most of the pumps we install in the heating game have run capacitors.

https://en.wikipedia.org/wiki/Motor_capacitor

 

[joni os]

Just replace pump with old style grundfos. Plenty around from systems made redundant by combi installs. Pump will probably outlast your boilermate.