Refrigerant handling: Heat Pump tips
Short, practical technician tips on refrigerant handling for heat pump. Check each one against the manual for your exact model before acting.
Check charge at the right outdoor temp
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>70 °F cooling, <40 °F heating; follow mfr.
Crankcase heater prevents flooded starts
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On off cycle refrigerant migrates to the coldest point — often the compressor. Oil foams on start, pumps out (oil slugging) and breaks valves/gaskets. Heater keeps crankcase ~30°F warmer. Heat pumps and outdoor units need one even when small.
Gas/oil furnace aux heat must never run with the compressor
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Hot furnace air across the indoor coil spikes head pressure and can burst the coil; verify interlock on every seasonal check.
HP TXVs are MOP/cross-charged
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Heat pump TXVs have limited vapor charge because the idle bulb sits on hot gas; don't swap in a standard AC TXV.
MOP TXVs stay shut during pull-down
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A gas-charged or pressure-limited TXV won't open until suction drops below its MOP — don't condemn it for staying closed on a warm start. Used on AC and heat pump coils.
Split-system charge is for a given line length
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Nameplate charge assumes a specific liquid line length; add per the tag for longer runs.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.