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Re:How a Heat Pump Works by helen___keller on Friday February 10, 2023 @09:25AM (#34739969)
I’ve been independently interested in heat pumps because I need to replace my old end-of-life system and I’ve been interested if a modern cold-weather mini split system is a better investment. There’s lots of conflicting info I’ve found on if heat pumps perform in freezing weather and at what kind of efficiency.

I’m sure there’s others in my position.

Re:How a Heat Pump Works by fullstop on Friday February 10, 2023 @09:34AM (#34740112)
Where do you live geographically? I'm in eastern Pennsylvania and have lived with a heat pump for 20+ years.
Re:How a Heat Pump Works by helen___keller on Friday February 10, 2023 @10:18AM (#34740729)
Massachusetts
Re:How a Heat Pump Works by fullstop on Friday February 10, 2023 @11:32AM (#34741926)
A bit colder, on average, than where I live. You might want to look at ground-loop HPs or ccASHPs.
Re:How a Heat Pump Works by sbradford26 on Friday February 10, 2023 @10:07AM (#34740573)
So largely I think the confusion stems from there being two major different "types" of heat pumps and they perform very differently.

The first is your conventional type system, this is usually what AC units are in the US. They run at maybe 1 or 2 speeds. These type of heat pumps are common in the southern parts of the US but also will be found paired with a gas furnace in the northern US. Since they don't adjust their output dynamically they tend to start losing capacity/efficiency significantly around 25-30F.

The second is an inverter driven heat pump. You usually find these in mini splits but they can also be found in a standard air handler form factor that would replace a furnace. The inverter allows the compressor to adjust based on demand and exterior temperature to maximize efficiency. This allow these units to operate efficiently down to -13F depending on the unit. Now there will still be some capacity loss at those temps so during the design of the system this has to be taken into account.

For detailed information on the efficiency of heat pumps I would check out NEEPs website. It is a great resource, it will show you capacity and efficiency (COP) of tons of different units across their operating temperatures.

https://ashp.neep.org/

Re:How a Heat Pump Works by kwhitefoot on Friday February 10, 2023 @10:22AM (#34740780)
Heat pumps sold in Norway are claimed to work down to -30°C. See, for instance, the Samsung Nordic Extreme: https://www.elkjop.no/product/hjem-rengjoring-og-kjokkenutst...

I don't know what the coefficient of performance is at that temperature though.

Re:How a Heat Pump Works by rayiner on Friday February 10, 2023 @10:25AM (#34740822)
I’ve got a mid-range Amana heat pump and even that has a COP of 2.1 (2 watts of heating per watt used) down to 0F.

Heat pumps require different system design than a traditional setup, where the cooling load is usually the driving force. You might need a bigger heat pump to handle the heating load in very cold weather accounting for the efficiency loss.