"John Rumm" wrote:

It might be you need to tackle the problem with more pump speed and then
sorting any pump over issues.

I believe that the pump over problems occur when hot water only is being
heated in cylinder.
The system is S plan with the hot water valve in the airing cupboard close
to the tank.
The CH valve is close to the boiler, I believe at the 15/22
upstairs/downstairs split.
I think that pump over occurs when the CH stops calling for heat and only
hot water demand remains.
Have increased the height of the vent loop to the apex of the roof, but
still seem to remember problems when running at pump speed 3.


What make/model of boiler is it?

Glow worm Space Saver 50 - yes I know this is old and a bit undersize after
all the mods.
I wanted to iron out the problems, then introduce new boiler and pump.



Thanks for input

Phil