If your unit is equipped with a compressor crankcase heater, the heater should be energized for several hours prior to starting the compressor. On some units the heater is energized when the control power circuit breaker is made. If the unit has been off for an extended period, energizing the heater overnight is good practice.
Before starting the unit, check oil level in the sight glass located on compressor base. You should be able to see an oil level. If you can't see a level it is sometimes difficult to tell if the crankcase oil level is low or is overfilled. Closer inspection with a focused-beam flashlight will help. Keep in mind that refrigeration oil is highly refined and under normal operation conditions is very pale yellow. If oil is not visible in the compressor sight glass, don't start the compressor until you can add more. Also check pressure gauges, paying particular attention to the suction pressure gauge. Some residual refrigerant pressure should read on the gauges. If they all read zero, the system refrigerant charge has leaked out. If the suction gauge reads zero, even though there is pressure reading on the discharge gauge, there might be a leak in the chiller. If in addition the indicator in the liquid line sight glass shows “wet”, it is time to call the serviceman. Running the system in this situation could compound a relatively simple repair job into a major one.
Make sure all refrigerant hand valves are open, including valves to control lines. Assure that the water in the tank is circulating through the chiller only (on bypass valves left open) and that the condenser pump is running raw seawater through the condenser. Switch the compressor on. If the compressor comes on, allow it to pump down the residual refrigerant left in the chiller before energizing the liquid line solenoid.
As soon as the compressor comes on, immediately check the oil pressure gauge. It should read significantly higher that the suction pressure gauge. If the oil pressure reading matches the suction pressure, there is no net oil pressure, and unit should be shut down immediately. Don't wait for the oil failure switch to do this, as it operates on a time delay.
Once the compressor has pumped down the system, it should shut itself off on the low pressure switch setting. This setting should never allow the compressor to pump into a vacuum; the suction gauge pressure at cutout should always be above zero.
Now, switch on the liquid line solenoid. The compressor should start when refrigerant pressure reaches the cut-in setting on the low pressure switch. After you have started the unit, you may see foaming in the compressor oil sight glass. This is normal as the suction pressure drops on startup. Once suction pressure stabilizes and temperature pull down begins, the oil level in the sight glass should be about half full. Note: on some compressor models the oil pump directs a stream of oil at the compressor sight glass. [top of page]