jack benson Posted February 1 Author Share Posted February 1 19 minutes ago, SteamyTea said: What am I missing? You are not missing anything, below is the clarification - both sides are 6 lpm. The water flows as follows: CLEAN WATER SIDE There are slight inconsistencies in the flow rates recorded by each sensor, but they should all be the same. MAIN COLD FEED becomes the SHOWER HOT FEED (The cold water is heated by our system from 7.6C to 40C). The MIX FEED is a combination of the SHOWER HOT FEED and SHOWER COLD FEED. In this example, because its winter and the cold water is very cold, the system heats the water to 40 C and does not require mixing with cold water, therefore the SHOWER COLD FEED is 0 lpm Therefore MAIN COLD FEED, SHOWER HOT FEED, MIX FEED are all the same water flows. The Flow rate of the clean water is 6 litres per minute. WASTE WATER SIDE The water that leaves the shower tray is marked as FROM SHOWER TRAY. After it leaves our heat recovery system it is shown as TO SOIL STACK. As this part of the system is pumped, there is some air mixed in with this water which explains why the flow shows at around 6.8/6.7 instead of 6 lpm. To heat 60 litres of water from 7.6C to 40C with no heat recovery would use 2.27 kWh - so i agree your calculations of about 71% saving. But traditional systems have other considerations: Hot water cylinder: You need to factory approx. 15% heat loss from a cylinder or hot water that is left in the pipes after the shower ends. Gas boiler: efficiency can range from 98% (theoretically) to 70%. Link to comment Share on other sites More sharing options...
jack benson Posted February 1 Author Share Posted February 1 14 minutes ago, Alan Ambrose said: The technology isn't often seen in the UK, so it would be good to make it available here. Weirdly enough I visited a property with something that looked like it today. Are you importing existing European tech? No harm in that btw. A French start-up owns the patent and i have spent the last year commercialising the product. We now have a production line up and running in France and a growing install base there. 16 minutes ago, Alan Ambrose said: Here's the list of drain heat recovery tech in PHPP right now. BTW getting your product in the PHPP spreadsheet would be helpful too - there's isn't much UK stuff in there. Any advise on how to do this would be appreciated Link to comment Share on other sites More sharing options...
SteamyTea Posted February 1 Share Posted February 1 2 minutes ago, jack benson said: There are slight inconsistencies in the flow rates recorded by each sensor, but they should all be the same. Not to worried about the odd litre or so, but I think I get what is happening now. 3 minutes ago, jack benson said: But traditional systems have other considerations: Ignoring that at the moment as it just muddies the water. So 2.27 [kWh] - 0.65 [kWh] = 1.62 kWh recovered. That would imply that somewhere there is a ∆T of 23.2 K. 4.18 [kJ.kg-1.K-1] x 60 [kg] x 23.2 [∆T] = 5,818.56 kJ or 1.616 kWh I can't work out how that ∆T is created, the closest is the ∆T between the 'from shower tray" 37.1°C and the 'soil stack" 11.4°C, ∆T 25.7 K. Using that, and it seems to make sense. 4.18 [kJ.kg-1.K-1] x 60 [kg] x 25.7 [∆T] = 6,445.56 kJ or 1.79 kWh which is in the same ball park as the 1.62 kWh. I do find the 88% heat recovery a bit high and would that number double checked. (I often get muddled with numbers, it is very easy to pick up the incorrect number when working out efficiency) Link to comment Share on other sites More sharing options...
jack benson Posted February 1 Author Share Posted February 1 1 minute ago, SteamyTea said: I do find the 88% heat recovery a bit high and would that number double checked. The water leaves the shower floor at about 37 C in this case and we pre-heated the cold water to about 34 C 37C - 7.6C = 29.4C - Temp difference between water leaving the shower tray and the cold water supply 34C - 7.6C = 26.4 C - Temp difference between the pre-heated water and the cold water supply 29.4C * 88% = 25.8 C - therefore the numbers stack up Link to comment Share on other sites More sharing options...
saveasteading Posted February 1 Share Posted February 1 If 17 minutes ago, SteamyTea said: 2.27 kWh If electricity is about 30p / kWh, that's a 70p shower reducing to 10p. Not allowing pipe losses. All -ish. 2 showers x 365. So a useful £400 ish per annum. Cost saving might still be a hard sell unless these become standard and cheap. I saw this launched by a young (red haired?) chap at a Pas de Calais Chamber of Commerce exhibition. Maybe the same chap. Link to comment Share on other sites More sharing options...
Mike Posted February 1 Share Posted February 1 48 minutes ago, jack benson said: Any advise on how to do this would be appreciated Here: https://database.passivehouse.com/fr/components/#certification-methods-info Though it looks like you'd need your 8 litres/minute upgrade to qualify. I agree that it would be a good place to be listed, in terms of your profile. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 1 Share Posted February 1 5 minutes ago, saveasteading said: I saw this launched by a young (red haired?) chap at a Pas de Calais Chamber of Commerce exhibition. Maybe the same chap. An old mate of mine (was also once my student) looked into it about 15 years ago. I never found out what the outcome was, I think the MVHR recovered more energy in his modelling. Link to comment Share on other sites More sharing options...
joe90 Posted February 1 Share Posted February 1 Having dealt with old pipework bunged up with crud in the past I would worry about trying to pump stuff out of a shower tray. Link to comment Share on other sites More sharing options...
jack benson Posted February 2 Author Share Posted February 2 14 hours ago, joe90 said: Having dealt with old pipework bunged up with crud in the past I would worry about trying to pump stuff out of a shower tray. is the shower waste pipe gets blocked you will have a problem showing whether you are using MWHR or not. as long as you power off our heater, it is safe to use normal drain un-blockers. when the pump is off, the water will go down the soil stack as normal Link to comment Share on other sites More sharing options...
dpmiller Posted February 2 Share Posted February 2 5 hours ago, jack benson said: is the shower waste pipe gets blocked you will have a problem showing whether you are using MWHR or not. as long as you power off our heater, it is safe to use normal drain un-blockers. when the pump is off, the water will go down the soil stack as normal how does the pump know to turn on, is there level sensing in the trap or does the pump run pulling air in too? Link to comment Share on other sites More sharing options...
jack benson Posted February 2 Author Share Posted February 2 12 minutes ago, dpmiller said: how does the pump know to turn on, is there level sensing in the trap or does the pump run pulling air in too? the pump is inside the water heater which is mounted on the wall. the pump lifts the water from above we do not install any electrics under the shower tray. the water heater has a flow meter inside that detects when the shower is in use and starts the pump Link to comment Share on other sites More sharing options...
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