Pump needs high setting, why?

[DIYPaul]

Hi all

I have a pumped/gravity fed heating system, about 10 rads. From what I've read, the pump should generally only require setting 2. However, the only way to get the house warm is to have the pump on its highest setting 3. Over the last year I've had a new pump, and the system powerflushed.

Is it unusual to require setting 3 on the pump? Is there anything else I can do to improve this? Could the motorised valves be gunged up and need replacing? I can't think of anything else that might impede the flow of water.

Thanks
Paul

 

[Rickster123]

What size is the pump? Nothing wrong with speed 3. If it all gets hot what's the issue?

 

[DIYPaul]

It's a Grundfos UPS 15-50 (exact same model as the old one that I replaced, which also was on setting 3). I've read that having the high setting can introduce air bubbles into the system that can cause cavitation and rusting of the rads.

 

[Howsie]

The Internet is a dangerous thing.

If its not over pumping then its fine on three if its working for you.

 

[Rickster123]

:iagree:

Close the airing cupboard door an get out in the fresh air!

 

[lambchop]

u most probably got lots of bends in the pipework so the pump has to be on its highest setting to overcome the resistance and get the heat round. just make sure you have inhibitor in the system

 

[DIYPaul]

ok, thanks guys.