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HVAC

Water-Source Heat Pump Not Cooling: Facilities Troubleshooting Checklist

For a water-source heat pump that runs but does not cool, verify thermostat demand, airflow, filter condition, loop-water availability, condensate safeties, and whether neighboring units are affected. Refrigerant and internal electrical diagnosis should be escalated.

Last reviewed 2026-09-12 · General facility-maintenance information, not a substitute for site procedures, manufacturer instructions, codes, or qualified professional judgment.

Diagnose then escalateSkill: Beginner–IntermediateTypical time: 15–30 min
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Safety boundary

Do not bypass safeties, open refrigerant circuits, or perform energized electrical diagnosis unless trained, authorized, and equipped.

Symptom → cause → first move

Fan runs, air not cool

Check: Compressor/refrigerant/loop/control issue

First move: Check loop pattern and alarms.

One unit hot

Check: Local issue

First move: Check airflow, controls, safeties.

Many units hot

Check: Loop plant/control issue

First move: Check shared system.

Repeated lockout

Check: Safety/equipment fault

First move: Record code before reset.

Weak airflow

Check: Filter/fan/coil issue

First move: Correct basic airflow.

What to check first

Bring these

  • Thermometer
  • Flashlight
  • Replacement filter
  • Camera/phone
  • BAS access if authorized

Before touching anything

  • Confirm the exact location and complaint.
  • Photograph labels, settings, and error codes before changing anything.
  • Know how to isolate water, power, or the affected area if needed.
  • Follow site-specific PPE, lockout/tagout, ladder, roof, and access procedures.

Step-by-step procedure

  1. 1Verify cooling callRecord room temp, setpoint, mode, schedule.
  2. 2Check airflowInspect filter, return, supply, and fan.
  3. 3Look for condensate troubleCheck pan, float switch, and pump.
  4. 4Check operator-visible loop dataUse BAS/gauges if intended for operator use.
  5. 5Compare nearby unitsMany affected units point to shared loop conditions.
  6. 6Record lockout/LED codeTake a photo before clearing anything.
  7. 7Escalate sealed-system/electrical workCompressor, refrigerant, and energized testing require qualified service.

Stop and call a licensed professional when

  • Refrigerant diagnosis is required
  • Electrical panel work is required
  • Repeated high/low pressure lockouts
  • Loop water unavailable building-wide
  • Water leak inside cabinet

Common mistakes

  • Condemning compressor too early
  • Resetting before recording codes
  • Treating shared loop issue as many local failures
  • Opening water/refrigerant circuits
  • Ignoring airflow

FAQ

How is WSHP different from split system?

It exchanges heat with a building water loop rather than its own outdoor condenser.

Can one loop problem affect many units?

Yes; shared loop conditions can affect many heat pumps.

Should I reset lockout?

Record the code first and follow site procedure.

Can dirty filter stop cooling?

Yes; airflow problems reduce capacity and can trigger safeties.

Tools for this work

Full kit
HVAC service wrench set20×20×1 air filter12×12×1 air filterAluminum foil HVAC tapeThermal cameraInfrared temperature gun

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