DIY solar heating

[IMM]

Look at:

[stejonda]

In message , IMM writes

but that's a US site and USD300 + shipping etc. sounds like it would take an awful long time to pay for itself!

[bigcat]

re drain heat exchanger:

Now what's $390CDN in pounds?

Ouch, =A3170. Time to diy then!

4 parallel microbores would be way easier to make than one half inch pipe, and would give better thermal contact as well.

NT

[IMM]

The figures are there. The £ is higher than the $ at the mo, so it is a matter of the shipping cost to add on.

You can make your own using two large bore copper pipes. One inside the other. The mains water is in the gap between the two. Using two reducing elbows and filing out the pipe stops inside the the fittings so the inner pipe can slip you can easily make one yourself. Once filed out you solder it up with a powerful blowtorch and wrap with insulation.

[IMM]

See my other post on a DIY. Which also has better thermal contact as there is no spiral piping.

[raden]

In message , IMM writes

It has been for as long as I can remember

[Brian Sharrock]

snip

...................that bit I understand ...

....................................I can even grasp this idea ....

...... I'm afraid that I get lost about here .... Can you provide a pointer to a sketch ?

[Mark]

FFS how many showers do you people have a day. Has anyone given the slightest thought to how efficient this will be, and the likely rise in temperature achievable. Even I cant be bothered to build one of these.

-- Mark

[Ed Sirett]

There are only two ways this will save energy.

1) You can set the shower to half heat (assuming it has such a setting). 2) The greater flow of water permits you to have a shorter shower.

I'd guess that it would take a few minutes before there was much benefit from the heat recovery (the shower tray has to be warmed up and the trap water and the waste pipe itself.)

The benefits would likely be taken mostly in improved luxury rather than reduced consumption.

[Mark]

And somewhere to fit the thing, did you note the size!

"GFX can cut one of the largest peak water heater loads, the shower, by

50%." Rollocks, did Dimm invent this You would save more energy per year by shooting the cat and boarding up the cat flap. Or trying to recover more of the lost heat going up the chimney/flue.

-- Mark

[IMM]

Sorry should have been tee.

Start again.. Lets have 15mm and 22mm pipe for understanding.

Parts:

- 1 three metre lengty of 22mm pipe

- 1 three metre lengty of 15 mm pipe

- 2 solder ring capilary 22mm x 22mm x 15mm tess. (that is a 22mm in the centre of the tee)

- File out the the 15mm stops of each tee to make then slip 15mm pipe. Easy enough, just elbow grease. Or drill it out if you have the right sized drill.

- Cut the 22mm pipe to 2.5 metres in length

- Insert the tee on the 22mm pipe at one on each end.

- Run the 15mm pipe though one tee anmd push it until it reaches the other end and run it through the slip of the other tee.

- Have the tees 180 dregrees to each other

- Solder up.

- Cover with insulation.

You then have cold water running through the 22mm tee and out the other tee warmed up. The hot waste runs down the 15mm. This is now an effective heat exhanger. The longer the better. I have done these over 20 foot in length ona solar water heater and it was very effective and very cheap.

You size up the copper pipe to suit eithe a shower or a full 110mm waste.

[IMM]

Another know-it-all. Do a Google on groups and type in gfx. If you did that first you wouldn't nake such an idiot of yourself. There are some Americans who have these installed and reported figures on them. The average temp rise is 17C. In effect it makes your cylinder bigger too. When showering they are effective because you are heating the incoming cold water with waste water simultaneously.

Domestic applications have a far loger payback than commercial. Heavy use of waste water would make it feasible, in places sucj as hotels. Make your own, as in solar panels, and the payback is quite quick. See my post on making one.

[Aidan]

Is that parallel or counter flow?

[Mike]

Sounds okay but surely for a long run the inner pipe - which appears to be unsupported except at the ends - will touch the outer in various random places and cause turbulence and resistance to flow. I don't know if this will be a problem or not so could you let me know what sort of peak flow did you get through the 20 foot long one ?

[IMM]

Counterflow.

>

[IMM]

So if you have a combi that gives 11 litres/min @:35C temp rise, then having one of these pre-heating the mains water to the combi will give and extra

50% temperature rise. In effect making that 11 l/min to approx 17 litres/min

[Mark]

Must be distant Dimm relatives of yours, theirs absolutely no way you are going to get a 17c rise in the normal length of time it takes most people to shower.

I have, see my original reply in this thread

I have that's even more crap and useless (22mm pipe LOL) then the Yanks 6ft thing.

HTH :-)

-- Mark

[Brian Sharrock]

AIUI, that's using Screwfix catalogue as an example part code D90193 ?

that's be (?) Hot(!) Cold out ^ Cold(!) Cold in 22 ------/ /----------------------- 22 Waste -Hot >15 ----->--->----/ /--->------------>---------15 Waste (cooled) ---------/ /-----------------------------

Out of interest; - how do you get from a 40mm plastic waste pipe onto a 15mm copper 'waste'? Isn't the 15mm waste outlet a trifle slow? BTW, a 'new' bathroom is on the list once I've got the correct tuits - I've indicated to my wife that I've only got square tuits left from the last big-job - So I'm genuinely interested in heat-recovery devices as I'm always annoyed when joules of decent heat-energy goes down the plug-hole after each bath. I'd also be interested in where-abouts the tepid (cold) water could be introduced into the domestic-hot-water system.

[IMM]

Yep. Could be compression too.

I can't understand the drawing, but I think you have it.

I gave 15mm and 22mm for an easy to understand example. I did say size the pipes up to suit the shower application. It makes a heat exchanger like this once in 15mm and 22mm pipe. These days plate heat exchangers can do the job as well or better. But using 15mm and 2mm is cheap, very cheap, as long as you have the space to run it. You can spiral it around a loft or basement, or under a floor.

See the web site I gave for gfx. They give e.g's. of how and where to connect. Using large bore copper pipe this should be easy enough to make and far cheaper than what gfx charge. It has to be fixed in a vertical position. When water goes down the drain it spirals around the outside of a pipe making this form of heat recovery possible.

[bigcat]

Mike:

I suppose technically it doesnt if youre wiling to risk replumbing it. Preferable to make it maintainable I think.

IMM:

reducing

Have you actually done this, at 20ft long? The reason I didnt suggest this approach is differential thermal expansion. I cant imagine how a soldered joint would survive in such a creation. Sounds like a real recipe for leakage to me. One could certainly do it with flexible copper tube, but I dont know where youd get that in such a large size.

why do you recommend 3m? And more to the point, why 20ft? Theyre usually 2-3ft.

why do you recommend solder, which is soft and cracks easily, when the

2 tubes have differential thermal expension?

why do you recommend insulation? I'm not clear why cold to lukewarm flow, which is what goes round the outside, would need insulation. Most of the time it just sits there cold. I would think insulation might trap condensate and cause mould.

I think if youve got insulation to play with there would be much more effective places to put it.

Where do you get the 110mm copper fittings? And how do you drill 110mm holes in them?

Brian:

You've got 2 options for the warmed water, and 2 options for the drain water.

warmed water can go either: to the cold input of the shower or to the cold fill on the house's hot tank.

And the waste side can handle either: the output from the shower or the total grey water drain output of the whole house.

The logical thing is to have it either handling shower in and shower out, or house in and house out.

_________________// preheating ___/__________________\____ ___________________________ drain \ _________________/ //

Fitting vertically gives ideal performance, but they also work well horizontal too. Note the 2 flows should go in opposite directions to get effective heat exchange.

Mark:

Of course. The payback is around 100% pa if youve got 4 people in the house. Thats why we're talking about putting them in during a refit. NT