Re: Central Heating Pump Ratings

anthony james · 2004-04-01T14:16:48+00:00

Thanks - having read the manual again last night I was planning tolook this up based on flow rate so you've saved me the effort. Theydont make things easy do they?It's a noisy beast so i very much doubt i'd hear it above the fan. However, it does seem to short cycle which is likely to be related. The boiler has a pump over-run facility which can be wired out ofcircuit (and of course has been) so a minor rewire would probablysolve the localised boiling i think i can hear when the boilerswitches off.I'd come to the same conclusion (he was from Keston after all andwasnt interested in actually doing the work) but am wondering aboutthe relative costs of getting the pump replaced now (when we've a lotof other expenses) versus shortening the life of the boiler slightlybut not having that cost for some years.the out and return pipes are 28mm (huge) for about a metre, thenreduce down to, i think 22mm down under the floor into a loop of about3m total length but a small section (maybe 20cm total ) of the loopnear the pump is 15mm (again estimated). If we had the pump replacedthat small section could go as well.You've lost me there - what would it look like and where would it be?. The system is plumbed in as S plan i think - seperate motorisedvalves on the DHW and CH, pump runs when either valve is open.

Apr 01, 2004 24 Replies

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IMM 22 years ago

Use a primary secondary pump setup. Run a 28mm "primary" loop from the flow of the boiler to the return. Put the large pump on the flow just after the boiler. At roughly the midway point of this loop insert two tees next to each other, as close as possible. The tee nearest the flow to the flow to the CH/DHW and has the smaller existing pump on it, or better still replace with a Grundfoss Alpha auto variable speed depending of system pressure, so TRV can be on all rads, and the associated zone valves. The second tee is the return from the DHW/CH.

This ensures full flow through the boiler at all times. Set the large pump on the "primary" loop to flow required, not too much, just keep it the right flow.

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Owain 22 years ago

"sunbeam" wrote | "IMM" wrote | > I love this Jocko humour. Do you know Billy Connolly? | Numbered any good bricks lately IMM?

Numberrred brrricks?

Couldna build a wendy hoose afore he ran oot ae fingers

Owain

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IMM 22 years ago

I just love this Jockoness. What a hoot.

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fred 22 years ago

One final shot, can you turn up the boiler stat on your model? The higher the flow temp, the more heat lost from the rads so more heat for same pump flow. I know this may take you out of condensing operation but your boiler will still be more efficient than a conventional in this mode. If you haven't already, balance the rads for 10-12 degree drop instead of the

15-20 normal for condensers - again for more heat per litre per second.

I sooo know where you are coming from with the costs & priorities thing.

Good Luck

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IMM 22 years ago

I would not do this. This boiler is not fitted correctly. The lower the boiler te,peraature the better until it is fixed. The lower the temperature differential between the flow and return the more heat is transferred. It is now Spring and it does not need to be on high temps.

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