5 ms·

I think GP is talking about heat pump water heaters that are working between the air in the room where heater is installed and the hot water. Very different fro

I think GP is talking about heat pump water heaters that are working between the air in the room where heater is installed and the hot water. Very different from what you are suggesting. It could still make sense if it is installed in a room with lots of waste heat, e.g. next to a clothes dryer and other appliances.

war1025 6y ago
> I think GP is talking about heat pump water heaters that are working between the air in the room where heater is installed and the hot water. Correct. Every heat pump water heater I've ever seen has the heat pump directly on top of the water tank. It's possible they make ones that tie into an external heat pump, but I've never seen one.
- fomine3 6y ago
  In Japan, separated heat pump unit / tank is pretty ubiquitous and never seen union unit. https://echonet.jp/introduce_en/gz-000505/ https://echonet.jp/introduce_en/gz-000505/
- MayeulC 6y ago
  Huh? That would indeed be pretty dumb. I would have at least expected a duct that pumps air from outside... Heat pumps make little sense if you don't have access to a thermostatic source, or indeed any "free" heat source.
  - war1025 6y ago
    The trouble with water heaters is you want hot water year round. Heat pumps are pretty ineffective once you get down close to freezing. So having an exterior air source heat pump would only make sense for maybe half the year in a lot of locations. Generally utility rooms in houses have a decent amount of waste heat anyway from being near the furnace, so it probably does work out decently a lot of the time. My in-laws have a heat pump water heater and it makes their basement noticeably colder in the summer, which is pretty nice.
choeger 6y ago
Err, what? The heat exchanger has to be outside the house of course! Who would even build that inside? That's crazy!
- semi-extrinsic 6y ago
  To counter that point, high-end tumble dryers are universally built with a heat pump that is all located inside the same room (it's even in the same device). It's because they are cooling air to dehumidify it (the drying part), then they pump the heat back into the same air to circulate back into the wet clothes. https://images.jifo.co/10180236_1567417620885.png https://images.jifo.co/10180236_1567417620885.png

war1025 6y ago

> I think GP is talking about heat pump water heaters that are working between the air in the room where heater is installed and the hot water. Correct. Every heat pump water heater I've ever seen has the heat pump directly on top of the water tank. It's possible they make ones that tie into an external heat pump, but I've never seen one.

fomine3 6y ago
In Japan, separated heat pump unit / tank is pretty ubiquitous and never seen union unit. https://echonet.jp/introduce_en/gz-000505/ https://echonet.jp/introduce_en/gz-000505/
MayeulC 6y ago
Huh? That would indeed be pretty dumb. I would have at least expected a duct that pumps air from outside... Heat pumps make little sense if you don't have access to a thermostatic source, or indeed any "free" heat source.
- war1025 6y ago
  The trouble with water heaters is you want hot water year round. Heat pumps are pretty ineffective once you get down close to freezing. So having an exterior air source heat pump would only make sense for maybe half the year in a lot of locations. Generally utility rooms in houses have a decent amount of waste heat anyway from being near the furnace, so it probably does work out decently a lot of the time. My in-laws have a heat pump water heater and it makes their basement noticeably colder in the summer, which is pretty nice.

choeger 6y ago

Err, what? The heat exchanger has to be outside the house of course! Who would even build that inside? That's crazy!

semi-extrinsic 6y ago
To counter that point, high-end tumble dryers are universally built with a heat pump that is all located inside the same room (it's even in the same device). It's because they are cooling air to dehumidify it (the drying part), then they pump the heat back into the same air to circulate back into the wet clothes. https://images.jifo.co/10180236_1567417620885.png https://images.jifo.co/10180236_1567417620885.png