On Feb 11, 4:40*pm, John Phillips
wrote:
On 2008-02-11, Roger Mills wrote:


Indeed. By contrast to the pump, a CH system's radiators and pipework
(including the boiler) will have a head (pressure) versus flow curve
where friction causes the head to *increase* as the flow increases.
Head is approximately proportional to the square of flow in pipework.


I always fit the 5m head pumps rather than the 3m ones as I find they
can be run on a lower speed setting without stalling.