On 23 Jan 2004 07:01:22 -0800, firstname.lastname@example.org (timegoesby)
A standard heating pump specification will show you graphs of flow
against head for each of the typically three settings.
Basically, as flow resistance (equates to head) increases, flow
In order for a system to work properly, the pump has to be able to
deliver the flow rate required to the radiators because heat transfer
is directly proportional to flow rate.
However, the pipework and the radiators and even the boiler will offer
some resistance. The pump has to be able to overcome those and
maintain the required flow.
There are a few ways to handle this.
The first is to do a complete arithmetic exercise for the system.
From the size of each radiator, once knows its output in watts. This
equates to a certain flow rate for a given temperature drop.
Pipework can be sized from that and in turn, the overall head
resistance for the system determined.
Given that, you can pick the pump.
tells you exactly how to do it.
Alternatively, if you are doing a pump replacement, then simply look
up the datasheet for the existing one and then if you are buying a
Grundfos replacement, there are datasheets on their web site for you
to pick an equivalent.
The third way is to pick a Grundfos Alpha pump. These are self
adjusting and alter their power level to deal with the required
head/flow There is a nominal setting control which will work for
almost all systems, but you can up or drop it if you want to do so.
They cost a little more, but from my experience of one they are very
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