In the oil reservoir, any refrigerant trapped within the oil is boiled-off and the oil is cooled and kept available. ESK oil reservoirs are normally equipped with sight glasses with float ball level indicators, for upper and lower level indication, and with two shut off valves.

The size of oil reservoir required is determined by the number of compressors connected, compressor oil charge, system refrigeration charge and operating conditions. In the following selection charts, you will find a guideline based on our experience with parallel systems.

Installation and start up
The oil reservoir should be installed at the same level or higher as the oil level regulat
ors. Every oil reservoir has to be equipped with a heater element.
During compressor stand still period the heat er should be switched on to prevent refrigerant migration into oil reservoir.
During start up of the system the oil reservoir should be charged with the compressor refrigeration oil up to the upper (or middle) sight glass. If the oil level in the reservoir will fall under the lower sight glass level, oil has to be added.

FL1 – Operation with R717 (ammonia) and R290 (propane)
ESK oil reservoirs types OSA can be approved for all hazardous fluids on request and are to be ordered with suffix -FL1. OSA units for R290, R600a, R717, R723 and R1270 applications will be fitted with welding adapters instead of the rotalock valve.


Max. allowable operating pressure (PS max) according to the temp. range

[1] Allow. operating temperature: 100 … –10°C → PS1: 31 bar
[2] Allow. operating temperature: –10 … – 40°C → PS2: 10 bar
Max. allowable temperature: 90 °C (green sight glass float ball)