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Intermatic Support

Why is an HP Code (High Pressure) Displayed on AHN and Traditional Series Heat Pumps?

Applies To

All AHN and Traditional Series Heat Pumps

Question / Problem

Why does my heat pump display an HP (High Pressure) code?

Warning: Power the heat pump off at the disconnect and breaker before cleaning, adjusting valves, clearing debris, or performing maintenance. Relieve system pressure and allow moving parts to stop. Do not bypass or jumper safety devices. For internal service, contact a qualified professional and follow lockout and tagout practices.

Common Causes / Conditions

  • An HP (High Pressure) code indicates excessive pressure inside the heat pump.
  • Common causes include restricted water flow, a faulty high-pressure switch, a thermal expansion valve issue, an overcharged system, or a control board malfunction.
  • An overcharged system is most common after recent service work.

Step-by-Step Resolution

  1. Verify the pump is running

    Confirm the pool circulation pump is on. If using a two-speed or variable-speed pump, operate it at high speed or a higher RPM during heating to meet minimum flow requirements.

  2. Check and clean filtration

    Clean the filter, pump basket, and skimmer baskets to restore proper water flow.

  3. Set bypass and remove restrictions

    If a bypass is installed, adjust valves so full water flow passes through the heat pump. Check for closed valves, clogged strainers, or collapsed hoses.

  4. Restore airflow

    With power off, remove leaves and debris from the coil and top grille. Verify required clearance around the unit, then restore power and confirm the fan operates.

  5. Reset and escalate if needed

    If the HP code remains, power the unit off for 15 to 30 minutes, then restore power. If the code returns, the issue may involve the thermal expansion valve, refrigerant charge, or control board. Contact Intermatic Technical Support or a qualified HVAC professional.

Tips / Additional Notes

  • Most HP codes are flow related. Increase pump RPM, clean filters, and verify valve positions.
  • Ensure proper airflow by clearing debris and preventing discharge air recirculation.
  • Do not repeatedly restart the unit if the HP code returns.
  • The heat pump may restart automatically once pressure returns to normal.
  • If the HP code persists, correct the underlying issue before continued operation.