CH Pump Size

[dal5band]

We currently have a Grundfos 15-50 (MKII) CH pump, fitted by the people who installed a new boiler for us about 10 years ago. Although it was Ok when it was new, this year we notice that some of the distant rads don't get hot.
The system is a Potterton RS 80, in a large 4 bed house with 16 rads (some places there are several smaller rads in one room to avoid doors etc.). The original pipe-work and most of the rads are over 25 years old, boiler and pump 10years old.
Would an upgrade to a 15-60 help ? Currently the 15-50 is on Max (3 setting). Are there likely to be any prolems due to over sizing ?

 

[Softus]

Would an upgrade to a 15-60 help ?

That would be treating the symptom, not the problem.

Currently the 15-50 is on Max (3 setting). Are there likely to be any prolems due to over sizing ?

No so much, but if your system is corroding and getting sludged up, then even the most powerful circulator in the known universe isn't going to halt its progress.

Was your system [ever] dosed with a corrosion inhibitor?

 

[dal5band]

I take your point but the system has had inhibitor added. I just changed a radiator and the one I took off was in good condition, (changed due to being in the way - fitted a smaller double panel) the pipe and valves were clear. However, it probably is sludged in places.

Leaving that aside, what is the approximate range of a 15-50 pump and a 15-60 pump - in radaitors (we have 16) or size of boiler (80K btu).


PS yes I have just re-dosed the system after the radiator change !!!

 

[Softus]

If you suspect sludge in places, then I would cleanse the system before changing the pump.

16 rads is a fair old number, but it isn't an exact science because a lot depends on length of pipe runs, number of bends, and pipework gauge.

If your 15-50 is giving out because of old age, then fair enough. However, pump ports and pump valves can get choked up, thus reducing the effectiveness of the pump.

What speed setting is the existing pump on, and has it always been the same?

 

[cso30]

Definately look into the cleanliness of your system, but if you are going to fit a new pump check the watt rating on it not just the head of pressure it can work to.

Most pumps are between 80-120 watts the higher it is the more powerful it will be!

 

[dal5band]

OK thanks - job for the summer then.