Preheating

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Preheating

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ken69

Joined: 17 Jul 2005
Posts: 316
Location: Norfolk

Posted: Tue Dec 20, 05 1:21 pm Post subject: Preheating
Does anyone know if pre-heating the domestic water (from the rising main), is worthwhile. Drawing some water off into a jug and let stand overnight is cheap and free (for drinks and cooking), but was thinking of maybe warming the pipe itself just before it enters the heating system and hot cylinder.A net gain of even 10p a day seems useful.

Behemoth

Joined: 01 Dec 2004
Posts: 19023
Location: Leeds

Posted: Tue Dec 20, 05 1:28 pm Post subject:
Off the top of my head I'm not sure it would be worth it. If you are physically heating the pipe - what's the energy source and how much does it costs. If you want to reach ambient temp, you would need sufficent quantity to stand around for decent amount amount of time that it might take up a lot of space and only work to cool your house down. But I'm no physisist.

Mat S

Joined: 07 Nov 2004
Posts: 282
Location: Leicester

Posted: Tue Dec 20, 05 1:43 pm Post subject:
Get the outflow of your bath, shower or washing machine wrapped round the rising main and capture the heat you're throwing away!

dougal

Joined: 15 Jan 2005
Posts: 7184
Location: South Kent

Posted: Tue Dec 20, 05 2:46 pm Post subject:

Ken, as always, the energy has to come from somewhere.

Mat suggests one means of using already-paid-for energy rather than wasting it.
If you aren't reclaiming such would-be waste, and you aren't gathering extra energy (like with a solar pre-heat), then it comes from your paid energy usage. Whether or not it is too small to notice is an entirely different question.

Using a solar pre-heat of about-to-be hot water is one of the most cost-effective applications of 'renewables' in an urban, domestic situation.
This might use an extra pre-heat watertank (which can even work with a suitable combi boiler) or a hot water tank with a second (lower) coil to allow the solar collectors to warm the coldest water as it enters the tank.
With the dual-coil tank, in summer there should be no need to use additional fuel to 'top up' the heat to a worthwhile temperature.

ken69

Joined: 17 Jul 2005
Posts: 316
Location: Norfolk

Posted: Tue Dec 20, 05 3:45 pm Post subject: preheating

I have two 20mm hot water pipes crossing at right angles to a 15mm rising main pipe, so was vaguely thinking of bridging the 1/4" gap with highly conductive material, and insulating,as you say Matt, but am still robbing 'Hot Water' to pay 'Cold Water'.,as you say Dougal. Might work if the pipes ran parallel for a distance.
Also had the thought that heated pipe wraps were available, say a metre or two long, run by electric. Similiar to greenhouse propagator mats and low cost to run.
Probably would never know if there was any savings.

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