Air-source heat pump outdoor unit beside a house in the snow
Generic photo: PeterEastern · CC BY-SA 4.0

Field pattern: heat pump runs nonstop in cold weather (normal long runs vs aux locked out or not wired)

Heat pumps lose capacity as it gets colder, and variable-speed units are designed to run almost continuously at low speed. Long runs are normal if the house holds setpoint. If the house falls behind, check whether aux heat is locked out too low, disabled by a compressor lockout setting, or not wired, before suspecting the refrigerant system.

Cross-checked ~45 min moderateBrands: All

Before you start

  • Strip heat is 240 V: CAUTION
  • Charge/pressure diagnosis is BLOCKED (EPA 608): refer if capacity is truly low

Diagnostic steps

Unlock all 7 steps with expected values

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Field pattern: heat pump runs nonstop in cold weather (normal long runs vs aux locked out or not wired) · OnCall Tech