Drainwater heat recovery units of this type rely on the surface tension of the water inside the drain to spread it out into a thin film covering the interior surface of the drain, maximizing surface contact for better heat transfer. That surface tension doesn't cut it against the forces of gravity if you lay the thing on it's side. They make some pretty stubby versions (as short as 18" from some manufacturers), but the total surface area of the center-bore drain counts- fatter & longer ==> higher return efficiency. To get ~50% heat returned at 2.5gpm flow you need about 48" potable wrap built onto 4" copper drain drain, or 60" wrap on 3" drain. Natural Resources Canada maintains a list of models that are third-party tested for efficiency under standardized conditions for apples-to-apples comparisons, and for different levels of government subsidy.
EFI in Westborough is a US distributor for Renewability ( PowerPipe), but the shortest one they list as standard product is 36" long. (They'll open an account and sell them onesie-twosie quantities over the phone if you have a credit card number, and they don't hose you bad with handling charges on the shipping either.) If that's too long, Renewability has a 4 x 30" that you can order off their website (at a full retail type price, so as not to compete with their distributors).
There is one vendor with a plate-type HX designed for horizontal apps, but I'd be inclined to think that the clog risk and loss of performance to sludge would be considerable with any plate type system. They don't have any NRCAN-third-party tested units that qualify for Canadian subsidy (yet), and the design seems to be evolving from an expensive all-stainless version from a couple of years ago to something else:
was:
now:
From a cost/benefit point of view, the payback on any of them is dead-slow for 1-2 person families heating hot water with natural gas, but for a showering family of 4 heating hot water with propane, oil, or electricity it's a pretty good investment. Since the drain has to flow while the hot water is running to get any heat return, it works great for showers, but not at all for baths.
EFI in Westborough is a US distributor for Renewability ( PowerPipe), but the shortest one they list as standard product is 36" long. (They'll open an account and sell them onesie-twosie quantities over the phone if you have a credit card number, and they don't hose you bad with handling charges on the shipping either.) If that's too long, Renewability has a 4 x 30" that you can order off their website (at a full retail type price, so as not to compete with their distributors).
There is one vendor with a plate-type HX designed for horizontal apps, but I'd be inclined to think that the clog risk and loss of performance to sludge would be considerable with any plate type system. They don't have any NRCAN-third-party tested units that qualify for Canadian subsidy (yet), and the design seems to be evolving from an expensive all-stainless version from a couple of years ago to something else:
was:
now:
From a cost/benefit point of view, the payback on any of them is dead-slow for 1-2 person families heating hot water with natural gas, but for a showering family of 4 heating hot water with propane, oil, or electricity it's a pretty good investment. Since the drain has to flow while the hot water is running to get any heat return, it works great for showers, but not at all for baths.
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