Stop now — do not troubleshoot further If any of the following apply, stop reading and act on safety first. Do not reset safety devices, bypass limits, or open gas or refrigerant lines.
  • Refrigerant hiss, oil stain, or suspected leak — EPA-certified technicians only; do not add refrigerant or open valves yourself.
  • Repeated high-pressure lockouts or breaker trips — one reset is not a fix; continued operation can damage the compressor.
  • Sparking, burning smell, or exposed live conductors — shut off at a labeled disconnect if safe to reach; 3-phase work requires a licensed commercial HVAC/R technician.
  • Roof access and fall hazard — do not open RTU panels or roof hatches without fall protection and training.
  • Do not force or strike reversing valve components — stuck slide diagnosis requires qualified HVAC/R technicians and proper tools.
  • Do not chip ice from a running outdoor coil — shut down per manufacturer procedure or call for service; damage and refrigerant release risk.

Important: These guides are general information for commercial operators, not step-by-step repair instructions for untrained persons. You are responsible for following manufacturer manuals, local codes, and your insurer’s requirements. A/C Dr. Naz is not liable for injury, property damage, food loss, or code violations that result from actions taken based on this content. When in doubt, call a licensed professional.

Caution Power off at the labeled disconnect before cleaning condenser coils or reaching inside panels. Where a guide allows a single control reset, try it once only — if the fault returns, stop and schedule service.
Safe checks Thermostat setting, doors closed, visible gasket damage, and breaker position — visual checks only unless noted.

Commercial Heat Pump Not Heating: Reversing Valve Logic

Direct answer: When a commercial heat pump is not heating in winter, the failure is usually in the mode-change path — thermostat call, reversing valve solenoid, defrost logic, or auxiliary heat — not automatically low refrigerant. Puget Sound shoulder seasons make mode-stuck and defrost faults common.

Cooling-only units use a different guide — see commercial AC compressor not starting. Service: commercial heat pump repair · commercial HVAC repair.

Safe checks before you call

Work through these in order. Stop at any red condition above.

  1. Safe check Confirm thermostats are in heat mode with setpoints above room temperature — schedule overrides and occupied/unoccupied setbacks are a common no-heat cause.
  2. Safe check Note whether supply air feels cool while the outdoor unit runs — cool discharge in heat mode often means stuck in cooling or extended defrost without auxiliary heat.
  3. Safe check From a safe vantage, look for heavy ice on the outdoor coil — prolonged icing without a defrost cycle points to defrost sensor or board faults.
  4. Caution — once only One mode-change or defrost reset per OEM procedure only — if heat does not return within a reasonable pull-up time, stop and schedule service.
  5. Caution Do not open roof panels, test reversing valve solenoids, or use field tools on live refrigerant circuits — qualified commercial HVAC/R technicians only.

Likely causes (what we diagnose on site)

When safe checks do not restore operation, we follow sequence of operation before replacing parts:

Reversing valve and solenoid — 24V call present but valve slide stuck; open solenoid coil or weak magnetism — the unit stays in cooling mode while the thermostat calls heat.

Defrost logic — Sensor out of calibration, board not initiating or terminating defrost, outdoor coil iced and blocking airflow — common on Puget Sound winter mornings.

Auxiliary heat — Electric strip or gas auxiliary not energizing during defrost — the building loses heat while the unit temporarily runs in cooling-mode defrost.

Controls and sequence — Staging errors, economizer/min-OA interactions, and shoulder-season transition faults after cooling season — verified against sequence of operation before parts.

When to call a technician

Call if heat mode blows sustained cold air, the outdoor coil stays iced, defrost will not complete, or auxiliary heat never engages during winter occupancy. Same-day diagnostics when capacity allows — send thermostat mode history and whether cooling worked last season.

Need repair, not troubleshooting? Commercial heat pump repair · Commercial HVAC repair · Greater Seattle & Puget Sound

Why is my commercial heat pump blowing cold air in heat mode?
Most often a failed reversing valve solenoid or defrost board fault. If the unit stays in defrost too long without auxiliary heat engaging, the building temperature drops quickly even while equipment runs.
What does a stuck reversing valve look like to facility staff?
Thermostat calls heat, fans run, but discharge air stays cool and the outdoor unit behaves like cooling mode. Voltage at the solenoid with no mode change points to a stuck slide — not a thermostat typo.
Is outdoor coil ice always a defrost problem?
Heavy ice that does not clear after a normal defrost cycle usually traces to defrost sensors, board logic, or restricted airflow — not something to chip away while the compressor runs.

Heat pump still not heating after safe checks?

Call (425) 535-8990 Request callback

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