Rack — One Circuit Down (Case Group Warm)
Supermarket rack: one case group is running warm while the other five circuits hold temperature. The night manager wants gas added to the rack; someone on shift has suggested shutting the whole rack down to see if it is that one. Unit: Medium-temp rack, R-448A, three parallel compressors, six display-case circuits with EPRs and liquid-line solenoids. This is a graded decision lab from Commercial Refrigeration / RAC — you choose each next check, readings fill in as you work, wrong turns are coached, and you are scored on cause, efficiency, safety and verification. It runs inside HVAC Technical Training — Paths A–D, about 15 minutes.
- Interactive decision labs
- Built by working technicians
- Path-based verifiable certificate
- Exam preparation only
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Where this lab sits
This is one module lab from Commercial Refrigeration / RAC. The full path builds the rest of the diagnostic sequence around it, each module ending in a graded lab like this one.
Studying for an exam too?
Free practice questions with explained answers, then come back to the labs. Exam preparation only — we do not issue EPA, NATE or other official credentials.
All diagnostic labs
- Residential No-Cool — Split System Not Cooling
- Residential No-Heat — Gas Furnace Short Cycling on Ignition
- Frozen Coil / Airflow Restriction
- Residential Over- and Undercharge — Poor Cooling Call
- Superheat / Subcooling Decision
- TXV Hunting — Temperature Swings
- Condenser / High Head — Walk-in Cutting Out on High Pressure
- A2L Safe-Handling Decision (R-454B)
- Walk-in Cooler Not Holding Temperature
- Ice Machine Not Making Ice
- Reach-in / Prep Table Not Holding Temperature
- Walk-in Freezer Defrost Fault
- Natural Refrigerant Safe-Handling Decision
- Rooftop Unit Not Cooling
- RTU Economizer Stuck — No Free Cooling
- RTU High Static — Low Airflow and Poor Cooling
- RTU Gas Heat — No Heat / Ignition Fault
- RTU First Start-up Sequence