Momentary brain alert:-)
Would running the shower waste and supply water through an efficient heat exchanger be practical?
I can see a matrix gathering crap but how about concentric piping? Or is this just a snake oil marketing opportunity:-)
Hell of a lot simpler just to ditch the electric and install a pump fed from the CW tank and DHW, or a HW/CW combi system if the OP has one, with a thermostatic control in the shower cubicle.
In message , Chris Hogg writes
Maybe. I was just thinking that the problem only arises for electric showers. You have the cold water supply and the waste water outlet in close proximity.
From the considered calculations I have snipped, every deg.C rise in the inlet is going to be found at the shower head.
Something that would have a *plug in* length of waste sized copper tube surrounded by an insulated sleeve with a couple of 15mm connections?
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The idea *may* have been discussed here once or twice!
Commercially, Heatrae make one, they're a bit shy on prices though, the aluminium version seems to be about £45, can't find a price for the copper version.
Worth that much for the improved SAP result:-)
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Maybe a consideration when thinking about the pipe runs. Without going to town about it, you might run the cold supply for the shower as close as possible to the waste and any central heating pipes.
Indeed.
Where did you find that price? Damned if I can fine a price anywhere on the web.
Have to laugh at the idea that a 2m vertical heat recovery unit "can be fitted in existing homes". The number of houses with 2m of accessible vertical drain under a shower must fall into the "hens' teeth" category.
Not saying that there's anything wrong with the logic of waste water heat recovery for an electric shower, just that if you don't get it in a new build, you'll probably never be able to retrofit.
The lack of any quoted prices rather suggests that it's not been a huge commercial success.
Tim
Dunno, I couldn't find it again afterwards, I think the "£45" I saw might well have been a banner ad for an EPC on the codestore webshop.
Something like this might be an easier retrofit
Maybe you could 'draw' some microbore through a die to flatten it slightly then coil it round a length of 22mm tube and shroud it in some large bore pipe lagging?
Some of their proposed installations didn't look viable anyway.
But why must it be fitted vertically? I suppose 2m x 1.5" of water weighs a bit but surely sagging shouldn't be a concern.
Is part L appendix Q still in force, since the ditching of the Code for Sustainable Homes?
The 110mm version of the PowerPipe version would be better for larger households, provided one person showers while another person uses the loo, so it can suck the heat out of the sewage ...
If it saved having to jump to a 10kW shower it would be worth considering. Mine's pumped from cistern so no help anyway.
I think I'd want a bit more than 22mm for shower waste:-)
Why on earth is that site so fussy about professional install?
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You want to maximise the waste water contact with the heat exchanger. In a vertical pipe most of the waste water will "stick" to the walls of the pipe in preference to going down the middle which maximises heat transfer. At least in theory. ;-)
Tim
Found a UK supplier? ;-)
It's not hard to find sites extolling the virtues of waste water heat recovery.
A darned sight harder though to actually find a product for sale!
Tim
well ok, some 42mm copper tube then, £30/length
Crud gathers in waste piping, so the thing would need to either be cleanable or oversized.
Pipe in pipe is often proposed, but suffers 2 issues. First you don't have the required 2 layers between waste and potable water. 2nd the end seals are affected by differential expansion, so detailing there matters.
NT
Lots of bathrooms are upstairs. For the rest you're stuck with horizontal e xchangers.
If you've got access to under a bath you've got space for 2x 5-6' of horizo ntal exchanger.
They're much used in industry, hotels etc, but not domestically.
NT
ISTR that being pipe in pipe. If it is, not compliant.
My plan was to fill the waste pipe with compacted sand, cap it, then wrap 4 parallel microbores round it. Wrapping them tends to flatten it somewhat. Add manifolds, solder the microbores in place along the bottom. Have 2 of t hese with a compression U shape joining them and fit under bath. Result is easy cleanable, twin walled, lots of contact area. Water draining speed is affected, feet might be in water during showers, but I don't see that being a problem.
Lagging is pointless.
NT
You could fit a 10kW shower:-)
That one isn't pipe in pipe, it's pipe wrapped around pipe, so two layers separating clean and dirty water, but the heatrae *is* pipe in pipe, yet it claims ...
"The MEGAFLO SHRU has been tested and approved to the UK water regulations. ? Water Byelaws Scotland. ? Water supply regulations Northern Ireland. ? All current building regulations."
Given you've gone to all the trouble to get heat out of the waste water, into the cold water, I'd have thought the last thing you'd want is to loose any of it back to the air ... but ... Heatrae says it musn't be lagged.
If you search for images I think you'll find that it isn't pipe in pipe.
Which is more or less exactly what Powerpipe is.
Tim
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