Grundfos UPS 15-50 Fault - blockage?

[BLIND]

Hello everyone! I've had a scan through the first 2 pages of 'Grundfos pump faults' but can't find anything similar to the problem I have.

I would like to know of possible causes of pump failure. There is power going to the pump, it was fitted in the correct orientation and it was working fine for 2 days before failing. It sounds like the motor wants to spin but it blocked or stuck, this causes back pressure and activates pressure release gate and cuts out boiler.

History: Boiler kept over pressurising and cutting out; replaced expansion tank but fault remained; replaced pump and that fixed it; 2 months on and same fault has returned; expansion tank still ok so thought it might be a dodgy pump so replaced it and this time it lasted 2 days before pump fault returned.

My background: I am a novice plumber who bought a house 1yr ago with a 15yr old boiler and water tank. On moving into the house, I had the boiler serviced and although old, I was advised that it was on good condition but the thermo coupling may need to be replaced at some point.

I am looking to get a local certified plumber in to help diagnose the problem but any advice is most welcome.

Thanks in advance.

Billy

 

[Riley]

Muck in the system is most likely issue

 

[jtsplumbing]

can you give some information on boiler, have you made sure that all valves are open ??

 

[Ch4 plumbing]

Pump valve partially closed and restricting flow!

 

[BLIND]

Riley - thanks. I presume some kind of power flush would be needed to clear the system?

 

[BLIND]

JTS - I'll update boiler specs tonight but all valves are open and pump was working well for 2 days before fault appeared.

 

[BLIND]

CH4 - I'll look into how and why the pump valve is partially closed.

 

[BLIND]

Thank you for your replies.:smile5:

 

[jonnyswamp]

I've had tired pumps straight out of the box, give it a tap when you have power to it and see what happens
If it's a bit of crud it may get dislodged, if not it'll need taking off and inspecting
You can also take the large chrome screw out of the middle of the body to see if the shaft is spinning, this doesn't neccessarily mean the impeller is turning though but it's an easy place to start your checks

 

[BLIND]

Jonny - Thanks, I'll give that a try. I have removed the bleed screw and the shaft is turning but still no pumping. If it is a bit of crud, I'll give it a tap with a hammer and disassemble if necessary. If that fails, what would you suggest?

 

[jtsplumbing]

From your description you have a system boiler, Boiler over pressurising would not be due to pump, does pump feel very hot ?? or is it spinning and nothing moving, if the latter then impeller is not spinning, and you have a faulty pump out of interest what make/model boiler do you have ? do you have a hot water tank ? what other controls on system ? Photos if possible.

 

[BLIND]

Jts - I'll take some photos this evening. The pump is very warm to the touch. I have a hot water tank.

 

[Ch4 plumbing]

if the pump is "turning" but not pumping then maybe isolate and remove the pump head to inspect, some times the impellar breaks off the back but the pump still appears to turn.

 

[Riley]

If they have a system boiler then the cover should not be off the boiler as he's not gas safe

 

[BLIND]