Instruction book
1904 0504 83 
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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.
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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  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: 
Ì
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. 
Ì
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. 
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The handle (V1) is completely turned out anti-clockwise. 
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. 
On fixed speed compressors, run the unit unloaded for a few minutes before  isolating the energy 
recovery system from the compressor. 
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In case of an open water system and/or if freezing temperatures can be expected, isolate the 
compressor water system and blow it through with compressed air.