First Run Commisioning
The first-run commissioning ensures your HVAC/refrigeration system is clean, charged correctly, and configured for optimal operation. This article walks through three key phases:
1. Evacuation and Refrigerant Charging
A. Deep Evacuation
- Connect a vacuum pump and micron gauge to the service port.
- Pull down to ≤ 500 microns; hold at that level for at least 10 minutes to remove moisture and non-condensables.
- Close valves, isolate the vacuum pump, and monitor for pressure rise—any rise indicates moisture ingress or leak.
B. Refrigerant Charging by Weight
- Attach refrigerant cylinder to manifold gauge set.
- Weigh in the exact charge specified by the manufacturer on the unit nameplate.
- Allow refrigerant to flow as liquid into the liquid line; switch to vapor injection on suction side if required.
C. Fine-Tuning by Superheat/Subcooling
- Measure suction-line superheat at the evaporator outlet.
- Adjust charge to achieve target superheat (e.g., 8–12 °F/4–6 °C) or subcooling (e.g., 8–12 °F/4–6 °C) per the spec sheet.
- Document readings for future performance benchmarking.
2. Startup Sequences and Control-Panel Configuration
A. Power-Up and Self-Test
- Restore power at the fused disconnect; observe initial control-board self-test flashes or codes.
- Clear any stored fault codes before proceeding.
B. Control Parameters & Setpoints
- Enter correct system type (cooling, heating, heat-pump) into the panel menu.
- Program thermostat deadbands, staging parameters, and minimum run times as per design.
- Configure safety limits—high/low pressure cut-outs, freeze-stat protections, and float switch actions.
C. Sensor Calibration
- Verify thermostat and pressure sensor readings against a calibrated handheld meter.
- Adjust offset or span settings in the controller to match actual values within ± 2 °F (± 1 °C) or ± 1 psi.
3. Verifying Performance (Temperatures, Pressures, Airflow)
A. Temperature Measurements
- Record entering and leaving air temperatures across the evaporator; target ΔT of 15–20 °F (8–11 °C) for A/C.
- Confirm condenser discharge air is within expected range (typically 20–30 °F/10–15 °C above ambient).
B. Pressure Readings
- Verify suction and head pressures on the manifold gauge; compare to manufacturer’s pressure–temperature chart.
- Ensure head pressure does not exceed design limits under current ambient conditions.
C. Airflow & Electrical Load
- Measure static pressure across filters and coils; confirm airflow (CFM) meets design (e.g., 350–450 CFM/ton).
- Check current draw on compressor and fans against FLA; ensure ≤ 110% of nameplate FLA.