HVACBuildingWrench repair guide

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.

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

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

In this guide

Match the symptom
Tools and prep
Step-by-step
Common mistakes
When to stop
FAQ

BuildingWrench troubleshooting rule: find the boundary of the problem before replacing parts.

Match the symptom before you touch anything

Good maintenance starts by describing what the system is actually doing. Use the pattern below to decide where to look first.

What you see	What it points toward	First move
Fan runs, air not cool	Compressor/refrigerant/loop/control issue	Check loop pattern and alarms.
One unit hot	Local issue	Check airflow, controls, safeties.
Many units hot	Loop plant/control issue	Check shared system.
Repeated lockout	Safety/equipment fault	Record code before reset.
Weak airflow	Filter/fan/coil issue	Correct basic airflow.

Tools and preparation

What to bring

Thermometer
Flashlight
Replacement filter
Camera/phone
BAS access if authorized

Before you start

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

Verify cooling call

Record room temp, setpoint, mode, schedule.

Check airflow

Inspect filter, return, supply, and fan.

Look for condensate trouble

Check pan, float switch, and pump.

Check operator-visible loop data

Use BAS/gauges if intended for operator use.

Compare nearby units

Many affected units point to shared loop conditions.

Record lockout/LED code

Take a photo before clearing anything.

Escalate sealed-system/electrical work

Compressor, refrigerant, and energized testing require qualified service.

BuildingWrench habit: Change one thing at a time, then test. That is how you learn what actually fixed the problem.

Common mistakes

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

When to stop and hand it off

Bring in qualified help when:

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

Frequently asked questions

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.

Related BuildingWrench guides

Leave the next technician better information. Record what you found, what you changed, the part number if anything was replaced, and whether the repair held through repeated testing.

BuildingWrench provides general educational information for commercial-facility maintenance. Manufacturer instructions, applicable codes, site procedures, and required trade qualifications always take priority.

← Back to HVAC