Has anyone any experience of shower heat recovery systems such as Showersave/Recoh-vert or Ecodrain? In particular, are they good enough to boost a combi's DHW supply sufficiently to cope with 2 decent showers at once?
My thinking is kinda as follows. If an ordinary boiler has a stated output of 16 l/m at a 35° rise with say a 5° mains input, that would mean 16 l/m at 40° which is roughly what an average shower is, meaning about 8 l/m per shower. However, if a Showersave or equivalent heat recovery device is used, the 35° rise on say a 20° pre-warmed mains input would mean 16 l/m of water at 55°, which would be then have to be mixed with cold water to reach a usable shower temperature. Worst case scenario with the cold mains at 5° in a 70/30 ratio to achieve 40° shower temperature, meaning nearly 23 l/m at 40°, but if the cold water supply to the shower could also be warmed to say 20° then the ratio to achieve 40° would be about 57/43, meaning 28 l/m at 40°.
I know that unvented cylinder and system boiler is the usual suggestion for 2 bathroom households, but this is going to be in 6 bedroom HMO where there could be a high demand for hot water which will have to be met (otherwise unhappy tenants) meaning I would have to err on the side of caution with regards to how big a tank I got and how long I have it on every day.
I really would like to go down the combi route if possible, as there would be no chance of running out of hot water and no need to heat a tank of water that may or may not be used, but the obvious flaw with combis is the relatively poor flow rate of hot water, unless you look at the really high flow models like the WB 550 which you tend to pay through the nose for.
So, has anyone any experience of these shower heat recovery devices, and, if so, how efficient are they when used in conjunction with a combi boiler?
My thinking is kinda as follows. If an ordinary boiler has a stated output of 16 l/m at a 35° rise with say a 5° mains input, that would mean 16 l/m at 40° which is roughly what an average shower is, meaning about 8 l/m per shower. However, if a Showersave or equivalent heat recovery device is used, the 35° rise on say a 20° pre-warmed mains input would mean 16 l/m of water at 55°, which would be then have to be mixed with cold water to reach a usable shower temperature. Worst case scenario with the cold mains at 5° in a 70/30 ratio to achieve 40° shower temperature, meaning nearly 23 l/m at 40°, but if the cold water supply to the shower could also be warmed to say 20° then the ratio to achieve 40° would be about 57/43, meaning 28 l/m at 40°.
I know that unvented cylinder and system boiler is the usual suggestion for 2 bathroom households, but this is going to be in 6 bedroom HMO where there could be a high demand for hot water which will have to be met (otherwise unhappy tenants) meaning I would have to err on the side of caution with regards to how big a tank I got and how long I have it on every day.
I really would like to go down the combi route if possible, as there would be no chance of running out of hot water and no need to heat a tank of water that may or may not be used, but the obvious flaw with combis is the relatively poor flow rate of hot water, unless you look at the really high flow models like the WB 550 which you tend to pay through the nose for.
So, has anyone any experience of these shower heat recovery devices, and, if so, how efficient are they when used in conjunction with a combi boiler?
