I've had a Grundfos Super Selectric UPS 15-50 pump running for about 8 years. The boiler is a 12-year old Potterton Kingfisher 2 (floor standing). Recently, I've found that the 3 ground floor radiators in the sitting room never get really hot, UNLESS I shut off the TRV valves on all the other radiators. Does this indicate that the pump needs replacing? Is there some way to be sure that this is the problem before I buy a new pump?
It is probably more likely the system is starting to sludge up and the radiators need balancing better.
With the heating off, remove the large screw on the end of the pump and using a large flat bladed screwdriver fit it into the slot of the impeller shaft. Does it turn freely? If so, the pump is unlikely to be faulty.
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