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Old 06-17-13, 12:52 AM   #1
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Default Heat pump water heater + bathroom exhaust fan

I've been reading Xringer's thread about his Airtap and am thinking about getting the similar Nyle Geyser HPWH with a Marathon tank. I figure this combo could easily last decades. Our tank is brand new though (just bought the house, seller put it in) so the Marathon could come later.

I've been thinking about ducting options and I had an idea I haven't seen mentioned anywhere. Our biggest use of hot water is showers. During a shower, we run the exhaust fan to blow warm moist air from the bathroom to the outdoors, and unconditioned make-up air is drawn from outside the house as a side effect. Well, how about we combine the bath exhaust with the HPWH? When we start our shower and the water heater tank starts cooling down, the heat pump will kick on. It could suck the warm moist air from the bathroom, dehumidify it, and the cool dry air could be dumped ... somewhere. Not sure of the best exhaust solution yet. Dumping back to the bathroom would help dry it out, but the cold air would feel unpleasant. Exhausting to the basement (where the water heater is) would be easiest, but there is no dedicated path for return air, so the geyser would be fighting static pressure and contributing to air pressure imbalance, wasting energy.

Maybe it could exhaust to behind the fridge. Then we'd be killing three birds with one stone. There isn't a good air return path between bathroom and kitchen, but under-cutting the bathroom door or adding a jumper duct could solve that.

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