... 4.R410a Air Source heat pumpModel: AW09,AW09B,AW10,AW10B,AW12,AW12B,AW13,AW13B,AW15,AW15B,AW20,AW20BLow temperature air to water heat pump :AW10 ... /L,AW13/LNormal air to water heat pump can work at above -10 degrees ,Low temperature air to water heat pump ...