Check Grundfos CH pump turning

[Rob Arthur]

We have 2 x circulating and 2 x shunt pumps (for redundancy - we live in an old council building). Please could you advise the best way to find out if a pump is rotating or not? Any of the four pumps running will vibrate the others, so vibration doesn't help. I tried this little compass device, but it only shows one pump rotating just at startup and the others won't spin it at all. If I remove the bleed screws, might that get the compass working? Is there a better way? I strongly suspect at least one of the pumps (possibly most of them) isn't working. Any help would be mightily appreciated.

 

[Gasguru]

Look at the gauges either side of the pump...when the pump's running you'll get a pressure difference between the 2 gauges.

 

[Rob Arthur]

Thank you, Gasguru. There is only a pressure gauge upstream, but that does drop on starting one of the pumps. I've also managed to get the compass meter working. The compass has to synch with the rotor, so starting the motor with the compass held over the bleed screw means it speeds up with the rotor, and stays synchronized. Just placing the compass over the spinning rotor doesn't work: The magnetic field is rotating so fast, the compass can't synchronize, so it just sits there, presumably seeing the rotor's magnetic field spinning, but unable to lock on.

So we definitely have one dud motor. I can check it out over the summer.

Thank you so much for taking the time to help.

Top Marks,

Rob Arthur