I am trying to diagnose an intermittent fault with our heating, which started a couple of weeks ago and has happened every 4 days or so since then. Long story short, I have 2 circulation pumps, typical Grundfos pumps. When the fault occurs both the pump bodies are hot but the pipework isn't. On both pumps I tried removing the central vent screws on the pumps to check if the shafts were rotating. On one pump it was. On the other I could not check because when I remove the vent screw water spews out under pressure and I had to replace the vent screw immediately. I did not want that amount of water spraying around electrical equipment.
The two pumps are on different electrical circuits. The one with the confirmed shaft rotation sometimes trips the trip switch on its power supply. This is not the cause of the fault: it only happens if I power down and power up again when trying to identify the fault. When I reset the trip switch and turn everything back on, the heating works correctly.
The heating is not having to work hard at the moment. The temperature outside has only been a few degrees below freezing. It can get much colder here, and no doubt will do so before too long.
The heating is a single zone system with approximately 1 million radiators.
So my questions:
- Does water from the vent screw indicate a fault on that pump?
- Does the fact that the pumps get hot indicate a pump fault? On both pumps?
Or could a fault on one pump block circulation causing both pumps to overheat?
Or would the same symptom result from blocked circulation elsewhere in the system?
- What should I do next to trace the fault?
The two pumps are on different electrical circuits. The one with the confirmed shaft rotation sometimes trips the trip switch on its power supply. This is not the cause of the fault: it only happens if I power down and power up again when trying to identify the fault. When I reset the trip switch and turn everything back on, the heating works correctly.
The heating is not having to work hard at the moment. The temperature outside has only been a few degrees below freezing. It can get much colder here, and no doubt will do so before too long.
The heating is a single zone system with approximately 1 million radiators.
So my questions:
- Does water from the vent screw indicate a fault on that pump?
- Does the fact that the pumps get hot indicate a pump fault? On both pumps?
Or could a fault on one pump block circulation causing both pumps to overheat?
Or would the same symptom result from blocked circulation elsewhere in the system?
- What should I do next to trace the fault?