"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Garry wrote:

Im struggling with the pump term "Pump Head". when used in central
heating application.

Is it the distance between the lowest point of the central heating to
the base of the pump.

Or

The distance between the highest point of the heating circuit to the
base of the pump.

Or something else.

Thanks

garry

Something else!

It's the pressure generated by the pump to overcome the friction losses in
the system, and thus to allow the water to circulate. If you look at a
pump's performance graph you will see that the head is highest at very low
flow rates, and lowest at high flow rates. [Think of the back pressure you
generate in the mains by putting your thumb over the cold tap spout].

The pressure is often expressed in terms of an equvalent static 'head' of
water (1 bar is approx 10 metres) but it has nothing to do with the
physical dimensions of your system.

A 5 metres head is a common term. Have a pump at ground level and a 8 metre
high plastic tube on the outlet straight up in the air. The inlet off a
tank next to the pump. A 5 meter head will pump the water up the plastic
tube 5 metres.


In water terms, head = pressure