How to get an extra 2 SAP Points?

[SteamyTea]

58 minutes ago, jack said:

The temperature was 34.6 ºC.

Hotter than my shower.

Not suggesting bath in your used water though.

[Triassic]

Interestingly, my Heating system is described as Average in the SAP summary. I asked why, apparently Its driven by the cost of electricity and will only get worse when they issue the next version of SAP. So much for installing an ASHP. Apparently installing a gas boiler would have got me more points!

 

 

Edited November 15, 2022 by Triassic

[saveasteading]

32 minutes ago, Triassic said:

installing a gas boiler would have got me more points

I refer you to the remarks I have made before re the knowledge of the BRE folk who designed and control the program.

[Dave Jones]

On 30/10/2022 at 16:43, ProDave said:

This water heat recovery thing.

 

When I have a normal length man shower (could be different for a long lady shower) when wiping down at the end, I find any water left is "cold".  My assumption being most of the heat in the hot water has been absorbed by it landing on the "cold" (room temperature) walls and floor.  So most of the heat is being absorbed by that, later to be released back into the room.

 

It would be interesting to lower a waterproof temperature probe into the shower trap and read the actual temperature of the water reaching the trap.  My suspicion is it will be a lot lower than the shower water temperature, so any theoretical heat recovery will be less than expected.

 

Like @SteamyTea I would like to see data.

https://recoupwwhrs.co.uk/documents/Recoup_WWHRS-Energy_Statement_Overview-Specification_Outline.pdf

 

[saveasteading]

I'd like to see how this is made, because a warm pipe running through a cold isn't going to do 50% heat transfer unless it is multicelled like a radiator or air recovery box.

I'm all for this working, but have been discounting the ones I have seen over many years...maybe sorted now.

 

As PD says above, the water isn't so hot by the time it reaches the drain. In a 'man shower' as he calls it, the tray is taking quite a lot of the heat out...which is heat recovery. In a long shower this changes. So 50% recovery of not as much as we would like.

 

These are only for cold feed instantaneous showers too, although with extra plumbing the cold to the mixer could go through these. Plumbing getting messy.

[dpmiller]

our IZI is a pretty massive helix of 10mm copper inside the drain pipe and the cold feed to the mixer goes through it

[jack]

35 minutes ago, saveasteading said:

I'd like to see how this is made, because a warm pipe running through a cold isn't going to do 50% heat transfer unless it is multicelled like a radiator or air recovery box.

 

I believe the drain at the top dumps water into the (much larger diameter) downpipe at something of a tangent, which causes the drain water to form a film over at least a reasonable proportion of the inner wall of the downpipe. 

 

The drain and incoming water are counterflow, which would set a theoretical maximum of 100% - not that you'd get anything like that in the real world, of course.

 

41 minutes ago, saveasteading said:

As PD says above, the water isn't so hot by the time it reaches the drain. In a 'man shower' as he calls it, the tray is taking quite a lot of the heat out...which is heat recovery. In a long shower this changes. So 50% recovery of not as much as we would like.

 

Based on the admittedly basic test I did (temp of water in the trap after a shower) above, I don't think you lose that much heat to the tray etc after everything warms up (first few tens of seconds, maybe).

 

42 minutes ago, saveasteading said:

These are only for cold feed instantaneous showers too

 

The installation diagrams linked above show several installation options, all based on ordinary hot-and-cold-fed showers.

 

To reach the higher claimed efficiencies, you have to connect the unit to preheat both the cold feed to the shower(s) (up to two is recommended with the model I used) and the cold feed to the DHW tank. Agreed that adds to the plumbing faff, but it's a couple of extra runs of pipe and you only do it once. 

 

Of greater concern might be how long the pipe run with preheated water needs to be to get to the shower and the cold feed to the DHW tank.

[Dave Jones]

2 hours ago, saveasteading said:

I'd like to see how this is made, because a warm pipe running through a cold isn't going to do 50% heat transfer unless it is multicelled like a radiator or air recovery box.

I'm all for this working, but have been discounting the ones I have seen over many years...maybe sorted now.

 

As PD says above, the water isn't so hot by the time it reaches the drain. In a 'man shower' as he calls it, the tray is taking quite a lot of the heat out...which is heat recovery. In a long shower this changes. So 50% recovery of not as much as we would like.

 

These are only for cold feed instantaneous showers too, although with extra plumbing the cold to the mixer could go through these. Plumbing getting messy.

 

i'll be fitting one during our build so will see how it does, i plan on insulating the waste runs to it from all the showers. 

[SteamyTea]

What always concerns me with anything to do with bath, shower and basin waste is blockages. Mainly girls long hair.

Add a heat exchanger into the mix and it is just adding complication.

Maybe a waste water to air recovery unit would be more practical during the heating season.

[Adrian Walker]

On 30/10/2022 at 14:55, SteamyTea said:

 

Has anyone seen independent data for waste water heat recovery.

Intuitively I feel it won't be brilliant, but never modelled it, and no one I know who has one, has actually measured it.

I feel it falls into the same category as co sensing boiler efficiency and multi foil insulation.

They work, but never get close to the headline figures.

 

If you're showering in the bath, it's best to leave the water in the bath to cool down / heat the house. Waste water heat recovery is a lot of extra plumbing. Using an aerating shower is better and a lot cheaper.

 

Edited November 17, 2022 by Adrian Walker

[Radian]

Just now, Adrian Walker said:

 

If your showering in the bath, it's best to leave the water in the bath to cool down / heat the house.

 

 

Same is true of our shower when the plughole's blocked with hair. A good 33l of warm water slowly making its way to the outside world. 🙄

[SteamyTea]

47 minutes ago, Adrian Walker said:

 

If you're showering in the bath, it's best to leave the water in the bath to cool down / heat the house. Waste water heat recovery is a lot of extra plumbing. Using an aerating shower is better and a lot cheaper.

 

Except in a small house like mine.  The humidity rises too high and if the extractor fan is on, the house gets cold quite quick.

Having MVHR would sort that to a certain extent.