Why cold is harder than hot
Compressor oil thickens as temperature falls. On a cold start the pump has to move oil that is far more viscous than at operating temperature, which means higher starting torque and a short period where lubrication is not reaching every surface at design flow. Simultaneously, any water left in the system from the previous run may be frozen in drains, traps or low points.
Before the first start
- Check the oil - level, and condition. Cold weather exposes oil that was already degraded.
- Confirm the heater - crankcase and control panel heaters, where fitted, should be working before the machine is asked to run.
- Free the drains - frozen condensate in a drain bowl or separator will either block or crack it.
- Check the room - an unheated room may be below the machine's stated minimum; ventilation that was adequate in summer may now dump heat you need.
- Look at the dryer - a refrigerated dryer has its own low-temperature limits, and a condenser coil packed with dust behaves worse in a cold room with poor airflow.
The first run
Run unloaded for a short period to bring oil temperature up before loading, then bring demand on gradually. Watch discharge temperature and oil pressure rather than assuming the machine will settle. If the machine is on a load / unload control, a cold start with heavy demand can cycle faster than usual.
Water is the real winter risk
The most common cold-weather failure is not the compressor but the water: condensate freezing in a low point, a drain line or an exposed trap, then either blocking the line or splitting it. Insulating or heat-tracing exposed drain runs, and verifying automatic drains actually cycle, prevents most of it.
Ambient limits both ways
Screw packages are typically rated to a maximum ambient of around 45 C, and the low end matters too. Reading both ends of the specification, rather than only the maximum, is what keeps a machine inside the conditions it was designed for.
Send us your working pressure, required flow and site conditions and we will propose a configuration. Contact OPPAIR.