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]

Hi
Have you checked with the manufacturer the angles they have to be installed. I have never had a faulty Grundfos pump, may be I have been lucky. When not used for a long time the spindle needs to be turned via the air bleed screw. With a lot of modern day boilers they will not start up if the water is not circulating they have a built in motion sensor. May be someone has adjusted the pump and set it in the wrong position, before you moved into the house a few degrees can make a big difference.
I have also had pumps not working due to sludge, disconnect the pipes and clean out, the sludge should be visible in or around the pipes close to the pump. You may have an air lock.

I've had a couple go wrong in the short space of time. I've also seen it where other components have given up and have caused the pump not to start spinning

 

[Voidbetween]

Check u have 240v at pump if you are electrical competent - Volt stick can give an indication of this if u r not.
With voltage present remove middle vent screw and check with small electrical screwdriver to feel if pump is turning - if it is apply a small amount of pressure - if u can stop pump turning easily the the pump motor is at fault