Solar Heating System Commissioning and Troubleshooting
Solar Heating System Commissioning and Troubleshooting
Commissioning proves the loop moves heat safely; troubleshooting finds why it does not. The exam covers flush/purge, flow balance, differential-controller setpoints, expansion-tank behavior, pressure relief, sensor verification, and a logical diagnostic sequence.
Flush and purge
Fill the loop with the correct glycol mix, then purge air at the highest point and at the pump suction until no bubbles return. Bring the loop to cold static pressure, usually 1–2 psi per foot of height plus 10–15 psi, and check the expansion tank precharge against the same static pressure. Run the pump and confirm flow before enabling solar control.
ΔT and controls
A typical controller turns the pump on at ΔT 15–20°F (8–11°C) and off at 4–5°F (2–3°C), with a minimum on time. If ΔT is high but the pump is off, check controller mode, sensor placement, relay output, and pump power-not the collector first. If ΔT is low at full sun, suspect low flow, air, a fouled heat exchanger, or a sensor reading the wrong location.
Worked example
Collector sensor reads 230°F, tank sensor 130°F, but the pump is off. ΔT = 100°F, so the controller should call for heat. Check the controller display for “manual off” or a high-limit lockout; then verify the pump relay is energized and the pump is not air-locked. After restart, confirm the collector sensor falls and tank temperature rises within 10–15 minutes.
Traps
Commissioning on a cloudy day and declaring success; using an IR thermometer on a shiny pipe; ignoring expansion-tank precharge; leaving the relief valve piped to a closed drain; and adjusting setpoints before removing air. Always record flow, cold and hot pressures, ΔT, and controller settings.