Attention: It is only allowed to turn the handle completely in or out. No in-between position is
allowed!
The oil cooler bypass valve (BV1) starts closing the bypass line and opening the oil supply line from the main
oil cooler (Co) at the lower limit of its temperature range. At the upper limit of its temperature range, the
bypass line is completely closed and all the oil flows through the main oil cooler.
BV1 must have a higher opening temperature (set point) than BV2 in order to prevent the heat from being
dissipated in the compressor oil cooler (Co) before the warm oil is fed to the oil/water heat exchanger when
using the compression heat as source for energy recovery. Thermostat BV1 starts to open at 75 ˚C (167 ˚F)
and is completely open at 90 ˚C (194 ˚F).
Energy recovery system in use (see drawing)
The handle (V1) of BV2 (bypass valve of the HE) is totally turned in clockwise.
• Compressor start-up
When the compressor is started up from cold, the oil temperature will be low. Bypass valve (BV2) shuts off
the oil supply from the heat exchanger (HE) and bypass valve (BV1) shuts off the oil supply from the oil
cooler (Co) to prevent the compressor oil from being cooled. The oil flows from the oil separator vessel (AR)
through the oil filter(s) (OF) back to compressor element (E).
All energy input is used to rapidly warm up the compressor oil. No energy is recovered.
• Maximum energy recovery
As soon the oil temperature reaches the set point (opening temperature) of bypass valve (BV2), the valve
starts closing off the bypass over the heat exchanger (HE) oil line, while gradually allowing the oil to flow
through the heat exchanger (HE). As the oil temperature rises to approx. 15 ˚C (27 ˚F) above the set point, all
the oil passes through the heat exchanger. The exchange of heat between the compressor oil and the heat
recovery water is maximum. The oil from the heat exchanger outlet flows via oil filter (OF), oil stop valve
(Vs - if present), compressor element (E) and separator (AR) back to the inlet of heat exchanger (HE). Bypass
valve (BV1) bypasses the oil cooler (Co) as long as the oil temperature remains below its set point.
Operation principle at different loads:
• Low consumption of recovered energy
In this case, the temperature of the oil leaving heat exchanger (HE) would become too high for the oil to
be injected into compressor element (E). Oil cooler bypass valve (BV1) will open the supply line to the
compressor oil cooler to allow the hot oil to be cooled in cooler (Co).
The amount of energy supplied to the water is adapted to the need of energy.
• Recovery water flow too high/temperature too low
In this case, bypass valve (BV2) will open the bypass line of the oil separator vessel, allowing colder oil
from heat exchanger (HE) to be mixed with hot oil from separator (AR). Energy is transferred from the
compressor oil to the water, but at a relatively low temperature level.
Energy recovery system not in use
The handle (V1) is completely turned out anti-clockwise.
Except for the opening temperature (set point) of bypass valve (BV1) (see Thermostatic bypass valves), the
oil circuit is the same as without installation of the energy recovery system.
No energy is recovered.
This situation should be considered as exceptional, e.g. in case of maintenance of the energy recovery system
or when no energy is required for a long period.
Instruction book
66 2920 1634 04
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