CH pump replacement concerns.

[diydave]

Hi. My Parker 15-60 130 pump has been running fine for 7 years at its highest speed. It has recently developed a knocking sound when hot and working hard (disappears on speed 2) but this is not fast enough for my 15 radiator bungalow. Bleeding the pump had no effect so I suspect it might be on its way out and am considering upgrading to a grundfos UPS3... but I see here on the forums that these pumps can give problems through being too powerful? Any comments? Might I be better with a Salus 100A or 200A which also have auto pressure facility. (Also much cheaper!)
Cheers
David

 

[John.g]

I interpret from the pump curves that the flowrate is 1.02m3/hr, 17.0LPM which, depending on the rads output may give a dT of 15C to 20C.

 

[John.g]

 

[diydave]

Apologies John. Typo on my part. Indicated flow rate is indeed 1.3 cu m per hour and your delta T of between 15 to 20 deg C across the boiler is spot on. Delta T across radiators is very variable because of thermostatic valves. Delta T across boiler drops when hot water cylinder calls.