Shower heat recovery unit

Heating, insulation, ventilation, VMC, cooling ... short thermal comfort. Insulation, wood energy, heat pumps but also electricity, gas or oil, VMC ... Help in choosing and implementation, problem solving, optimization, tips and tricks ...
BobFuck
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Shower heat recovery unit




by BobFuck » 14/12/12, 13:59

I finished the bathroom.

It is an Italian shower, at ground level, but with a grating made of synthetic terrace boards, comfortable, warm underfoot.

Image

The blades are glued together:
- half with Cyanolit Koltout (from MS): take off after one month
- the other with Swiss-German polyurethane (Sikabond AT): as usual, it holds.

Below, a copper coil, cold water flows through it.

Image

It is a counter-current exchanger (cold water inlet on the drain side). The heated cold water arrives at the mixing valve which manages for the mixing.

The installation is quite annoying, it must be well pressed on the ground otherwise the water passes below.

Disadvantage: it is necessary to clean the exchanger (2 minutes 1 time per month) to remove the hair, etc.

Cost: nothing (I had copper).

Hot water savings: around 30% (roughly equivalent to 2 PV solar panels, lol).

When I have time, I will put more copper (I have a ring that drags), it should increase the yield.
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by Christophe » 14/12/12, 14:31

It's boooooooooooooo! Bravo! And superb idea for the coil, much simpler and more efficient (and above all durable) than heat exchanger recuperators for showers sold in addition a fortune (depreciable in 100 years of memory ... approximately see this subject: https://www.econologie.com/forums/recuperati ... t6546.html ).

You will inspire me there, I also have a bathroom renovation project!
I would also make a recuperator of this type in my case!

For glue, Sika products are good! When I take it it is with my eyes closed!

On my current construction site, I could notice that certain bombs of PU foam held 3 times more than others ... at equivalent price. In short there are really scams on this market (also) ... Avoid the green and white brand ... I would talk about it at the end of the site (waste photos)

Why didn't you screw the slats?

Congratulations again!

ps: practical question I presume that an "automatic" mixer is mandatory?
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by chatelot16 » 14/12/12, 15:25

Anyway who wants to save hot water must necessarily start by putting a good thermostatic mixer, just to avoid unnecessarily running water to make the settings, and avoid letting it run permanently so as not to have to settle again

with a thermostat you open or close as you want, always having the right temperature
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by Christophe » 14/12/12, 15:40

chatelot16 wrote:with a thermostat you open or close as you want, always having the right temperature


Uh yes that's the theory ... in practice provided you have a DHW loop (very rare in individuals) well there is always a mess in the pipes ...
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BobFuck
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by BobFuck » 14/12/12, 16:16

> Why didn't you screw the slats?

I had no stainless steel screws on hand ... if the polyurethane is blocked, that's what I will do, but from below, to hide the heads.

> ps: practical question I presume that it is mandatory
> an "automatic" mixer?

Yes, obligated. It compensates well for temperature variations, in use there are no problems. When I turn off the tap and open it again after soaping, it's a little warmer for a second or two, nothing serious.

> Uh yes that's the theory ... in practice provided you have a loop
> ECS (very rare in individuals) well there is always a mess in
> pipes ...

The water heater is just behind the left wall in the photo so the hot water takes 1 second to come, there is 2m50 of hose (it is made for : Mrgreen:). In addition it is PER so it does not cool in 2 minutes ...

In my old apartment the gas boiler that heated the water was at the other end, it took forever for this to happen, and the huge temperature variations ... zero comfort and maximum waste!

Otherwise, well, it gets dirty, you have to clean it, that's the problem, after 2 months it's dirty, but it takes 2 minutes. But if the exchanger is well hidden in the cellar (like the commercial models style pipe) and not cleanable, we do not see that it is disgusting and clogged everywhere and that it does not exchange anything, so ultimately, it's not worse!

If it had to be done again (for Christophe then):

- I would put a door (the curtain touches the ground but does not go to the ceiling, hence a small draft ... when the curtain did not touch the ground, it was a huge draft) .

Problem, the shower stalls that we find in the trade, it's shit, boring to ask, it leaks, it's ugly, it's all plastic, you clean a little hard it scratches, joints silicone everywhere that mold, doors not practical, etc ... so rather a door and tiles, all without drafts, but you need a mouth of VMC in the ceiling if you do not want to eat the paint on the face because of humidity!

- I would put a resin shower tray with the coil inside (there I could not because of the custom dimensions, and the fairly reduced thickness of the slab).

You'd have to find one with the drain in the middle.

Cold water must remain in contact with the tube for a long time: if it is 5mm above the bottom, it goes directly into the hole ...

Ideally, the grating should press a little on the tube.

I built it like a walk-in shower (flexible PVC membrane), but without the slab and the tiles on it.

- And a wooden grating (the composite one weighs 15 kg), but it is top class and warm under the toes

- And longer tube
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by Christophe » 14/12/12, 17:05

Thanks. Noted! Image
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by Christophe » 14/12/12, 23:18

Small note: what if you made sure that the used water flows by following the spiral? Doable according to you? For the moment it is not the case if?
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by BobFuck » 15/12/12, 11:57

This is what I wanted to do originally, but for it to end up emptying, so as not to have a stagnant puddle, there would have to be quite a slope. However, the shower is on the ground floor, and the drain was not low enough, it was borderline. I already dug the slab to put the siphon ...

Should the grating press on the tube (with a kind of foam not too rigid), like that when there is someone in the shower, it drains slowly, but when there is nobody, it empties good. Or put a piece of foam on the drain which slows the flow only when there is someone in the shower. It's not an exact science ...

I thought about the thing and I tell myself that:

- the efficiency depends mainly on the exchange surface
- the cost is almost entirely in copper
- so you have to maximize the surface area / kilo ratio of copper, i.e. minimize the price / m² of exchange area

As the copper tubes all have about a 1mm wall, and the price of the tube is not far from the price per kilo of copper, the diameter of the tube does not matter much, in fact. They are all roughly the same price / m².

And so, it is better to immerse the tube of cold water in the shower water (we use its entire surface).

On the other hand, the exchanger which is in the Canadian PDF (large copper pipe with small pipe twisted around) is 3x more expensive because the exchange surface is just that of the large inner tube ...

If your shower is upstairs (like, you have the garage below), something like that could be better:

Image

A 100-150 PVC tube, with a copper coil slipped inside, the coil being rolled a little bit bigger so that it presses a little against the edges and stands alone. After that, just send the shower water along the edges, and for cleaning, a kind of big brush should do it.

Besides, if you put a siphon after this thing, it will prevent the exchanger stinks of shit during cleaning : Mrgreen:
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by oli 80 » 15/12/12, 12:15

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