The US Senate just approved an HFC ban. So which refrigerant should be used in the heat pumps? Can we get HFC-free heat pumps today?
See https://www.danby.com/blog/danbys-commitment-to-remain-100-h...
http://hvacrfundamentals.blogspot.com/2019/06/appliances-wit...
Looks like r600a, iso-butane is already in use.