The compressor room is too hot, the cooling air is being recirculated, or the installation doesn't allow enough fresh air in. The number one cause of overheating.

What you'll see

The compressor shuts down on high temperature, typically around 110-120 degrees C (230-248 degrees F). It might run fine in winter but trip constantly in summer. Or it runs fine with the doors open but overheats with doors closed. The compressor room itself feels hot -- sometimes surprisingly hot, even if outside temperature seems reasonable.
Before you assume this is the problem

Before blaming ventilation, do a quick check: is the oil level OK? Is the oil cooler clean? Is the thermostatic valve working? A compressor in a well-ventilated room can still overheat if the oil cooler is clogged or the thermostat is stuck. See: Clogged Cooler, Oil Quality Issues.

Could also be:

See all causes of overheating →

How to diagnose

  1. Measure the compressor room temperature

    Put a thermometer in the compressor room while the machine is running. Not outside the room -- inside, where the compressor actually takes in its cooling air. Most compressors are designed for a maximum ambient temperature of 35-40 degrees C (95-104 degrees F). If your room is above that, you've found the problem. In hot countries (Middle East, India, parts of Africa), ambient alone can be 45 degrees C+ before the compressor even adds its own heat.
    Result: Room temp above 35-40 degrees C = ventilation problem confirmed.

  2. Check for hot air recirculation

    This is the sneaky one. The compressor blows out hot exhaust air. If that hot air can't escape the room fast enough, it gets sucked right back into the compressor's cooling air intake. I've seen this many times -- the room doesn't even feel that hot to you standing in it, but the compressor is cooking itself in its own exhaust. Check: where does the hot air go? Is there a clear path out? Is the compressor stuck in a corner or a small enclosure?
    Result: Hot exhaust recirculating back to intake = guaranteed overheating, even in a cool building.

  3. Check inlet and outlet ducting

    If ducting is installed, check that it's not blocked, kinked, or undersized. Atlas Copco specifies a maximum pressure drop of 30 Pa in cooling air ducts -- if more, you need an outlet fan. Maximum air speed through cooling grids should not exceed 5 m/s. If there's no ducting at all and the room gets hot, that's probably what you need to install.
    Result: Blocked or missing ducting = insufficient cooling airflow.

  4. Check the cooling fan

    Is the cooling fan actually running? Is it running in the right direction? On some machines the fan is electrically driven separately from the main motor. A tripped breaker or bad fan motor means zero cooling airflow through the cooler. Also check if the fan blades are clean and undamaged.
    Result: Fan not running or running wrong direction = no cooling regardless of room temperature.

How to fix it

  1. Install proper ducting

    The best fix for hot rooms: duct fresh outside air to the compressor intake, and duct the hot exhaust air directly outside. This way the compressor always breathes cool, fresh air regardless of room temperature. Size the ducts according to the manufacturer's spec -- too small creates restriction and defeats the purpose.

  2. Add exhaust ventilation

    If ducting isn't practical, add exhaust fans to the compressor room to remove hot air. Make sure there's also a fresh air inlet on the opposite side of the room from the exhaust -- you need airflow through the room, not just a fan fighting against a sealed space.

  3. Relocate or reposition the compressor

    Don't install a compressor in a corner, a closet, or right next to a heat source (furnace, boiler, process equipment). It needs space around it for air circulation. If the current location is just wrong, moving the machine is sometimes the only real fix.

Common mistakes

Don't assume the room is cool enough just because it feels comfortable to you. You're not running at full load generating 30+ kW of heat. Measure the actual temperature at the compressor air intake. Also: opening the compressor enclosure doors is NOT a permanent fix -- it's a diagnostic trick. If it runs fine with doors open but overheats with doors closed, the problem is airflow through the enclosure, not the compressor itself.

Parts & tools

Thermometer or temperature gun for measuring room and component temperatures. Ducting materials (flexible or rigid, sized per manufacturer spec). Exhaust fan if needed. No special compressor parts required -- this is an installation fix, not a machine fix.

Review safety precautions before starting →

Safety

Let the compressor cool down before working on it. The discharge piping, separator vessel, and oil can be extremely hot -- 100 degrees C+ (212 degrees F+). Burns happen fast.

This issue can also cause

  • High Energy Use Excessive power consumption or unexpectedly high electricity bills, often caused by control problems, air leak...