Electricity Usage of CH Pumps

[Rod]

Relative has CH problems and (at last) got a CH person in to look. Pump & whatever motorised valve thingy she has look bad. She has now got a quote for their replacement.

So out of interest I went off looking at the various pumps available and specifically remembered Grundfos Alpha pumps being pretty well thought of. (Or is that a false memory?) Seems they are now very much claiming green credentials due to energy saving features of their pumps, and most especially their Alpha 2 models. Many years ago I had passingly thought about electricity usage by CH pumps but had just dismissed it as minor. Now I see Grundfos claim that one of their pumps could 'save' 368 kwh a year in a small house.[1]

That is a significant saving (but maybe not enough to cover the incremental cost of that pump over the next best ordinary Alpha). Is it realistic? Do pumps really use that much electricity in the real world?

[1] Number remembered from their excessively Flash-laden, slow web site. I really don't want to go back there to re-check.

[dom]

368 KWh (or units) sounds *just* possible. I think max power consumption of a Grundfos 15/60 pump was 100W - so it would have to be running for most of a 24 hour period, for many months of the year and at its maximum power setting.

In practice, I would expect its power consumption to be a great deal less.

[Dave Liquorice]

Call that 1kwhr/day pumps are around 100W. Does yours run for

10hrs/day?

Ours might in the middle of winter with the heating going flat out but for 3 or 4 months of the year the heating doesn't come on at all. But that is still only consuming what they say is a saving to make a saving it would have to be on an awful lot more.

[Rod]

We have our living room at around 17 C so remarkably little of the year do we need more than a little topping up.

I think what really struck me was how much electricity another pump would have to use to allow the Alpha 2 to save that much. And as you rightly say, how much of the time it would be running in a normal house.

And questions about when a pump actually uses the most electricity - when pumping maximum rate effectively? Or when pumping with very little water movement?

[Andy Champ]

Occurs to me that the power will end up in the hot water circuit - so the cost won't be the cost of the power, but the difference in cost between gas and electrickery. Might affect the sums.

Andy

[cynic]

Mostly marketing bullshit. Try looking at a power curve graph for any centrifugal pump