Daikin EWWQ-AJYNN Service Manual page 120

Maintenance
1
Lubrificating oils
3
Crankcase and oil
separator heaters
5 5
5–8
Besides lubrificating the bearing and other moving parts, the oil has the equally important task of
sealing the clearances between the rotors and other potential leakage paths thereby improving
pumping efficiency; the oil also assists in dissipating the heat of compression. The amount of oil
injected is therefore well in excess of that required for lubrification only.
Lubricating oil approved for use with the Screw compressor in this type of unit is POE Emkarate
RL220H. The oil differential pressure switch monitors the pressure differential between oil injection
pressure and compressor suction pressure.
After the compressor has started and been in operation for a short time, allowing sufficient time for the
system pressure differential to become established, the oil differential pressure switch is brought into
the safety trip circuit. Oil is now being supplied to the compressor under the action of the system
pressure differential, monitored by the switch. If the pressure differential falls below the switch contacts
'break' setting and the oil differential pressure switch trips and stops the compressor.
Because the oil pressure is generated by discharge pressure, a minimum discharge pressure must be
maintained; this minimum pressure increases as the suction pressure increases in order to maintain
the pressure difference required.
The function of the heaters is to prevent oil diluition with refrigerant during compressor shutdown,
which would cause foaming and consequent reduction in lubricating oil flow to the moving parts.
Electric heaters are energized every time the compressor shuts-down.
Warning: Verify the heaters have operated for at least 12 hours prior to start-up.
ESIE07-05
Part 5 – Maintenance