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High Compressor Discharge Temperature (>107°C scroll, >120°C recip)

Likely causes

Low refrigerant — suction gas can't cool the motor windings

Check: Low-side gauge below normal (R-22 normal 4.5–5 bar, below 3 bar = low), bubbles in liquid sight glass, superheat >15°C. Point IR thermometer at discharge line directly — scroll near 100°C = caution, >110°C = stop now

What to do: Leak check first (electronic + spray) → repair leak → full recovery → evacuate 500 micron, 30 min → weigh-in charge. No top-offs. After charging, verify discharge temp below 100°C and superheat 5–10°C

Excessive superheat — TXV/EEV starving or sensing bulb issue

Check: SH = suction line surface temp − low-side saturation temp. >15°C = excessive. Check sensing bulb location (12 o'clock, fully insulated), capillary for oil traces (leak), and TXV adjustment screw position

What to do: Adjust TXV superheat: turn adjustment screw 1/4 turn counterclockwise to lower SH, wait 15 min to stabilize, remeasure. Target: 5–10°C for scroll, 8–15°C for reciprocating. If capillary damaged or bulb leaks, replace TXV assembly. For EEV, verify controller SH setpoint

Poor suction line insulation — heated by hot surroundings

Check: Visually inspect entire suction line — missing, torn, or UV-degraded insulation. Focus on sections passing near boiler/machine rooms. Temp rise >3°C along the line indicates severely insufficient insulation

What to do: Reinstall closed-cell elastomeric insulation (e.g., ArmaFlex) 13–19mm thick over the full length. Glue/tape all seams tightly; add UV jacket where exposed outdoors

Excessive compression ratio — elevated condensing pressure

Check: Calculate absolute high/low pressure ratio — scroll normal 3–5, recip 3–8. Ratio >10 is dangerous. Check simultaneously for condenser fouling, fan failure, rising cooling water temp

What to do: Fix the condensing side — clean condenser, restore fan/cooling water flow, check tower water temp. Consider condenser upsize if undersized. Discharge temp drops automatically once condensing pressure is back to normal

Oil degradation/carbonization — lubrication failure

Check: Inspect oil via sight glass — clear amber = normal; black or cloudy = degraded. Test acidity with test kit — normal green; acidic = yellow. If system ran hot for a long time, oil change mandatory

What to do: Change oil — use manufacturer-specified type and viscosity (never mix POE/PAG/mineral). Drain old oil via drain plug, replace filter drier at same time, run 30 min and recheck. If oil degrades repeatedly, find the root cause (overheating, leak, oil cooler failure)

Field tip

Measure discharge temp on the pipe surface within 15 cm of the discharge service port using an IR thermometer — the port body itself reads inaccurately. Scroll max 127°C, reciprocating 135°C — always check manufacturer spec, and chase the cause even if it's below max but consistently hot.

All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.

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