Sub zero heat pumps

‘The conditions for the prototypes are that they have to deliver 100 per cent heating capacity without the use of extra heating sources and high efficiencies at 5° fahrenheit (-15° celsius)…Bosch, Daikin, Midea, and Johnson Controls join Lennox International, Carrier, Trane Technologies, and Rheem in the next phase of the challenge…Bosch says it can keep operating in temperatures down to -15°C and still function at -25°C’

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