Cooling Capacity Control; Figure 24 - Capacity Control Mechanism For Fr3100 Compressor - Daikin EWYD-BZ Series Installation, Maintenance & Operation Manual

Cooling capacity control

The compressors are factory-equipped with a stepless cooling capacity control system.
An unloading slide reduces the intake groove volume and its actual length. This slide is used to operate the compressor
at minimum and maximum load, and as in all other conditions the cooling capacity is adjusted by the inverter, which
modulates the speed of the screw (for further details on how the inverter works, please refer to the enclosed Combivert
manual).
The unloading slide is controlled by the pressure of the oil coming from the separator or by the effect of oil released to
the compressor suction; a spring provides the balancing force needed to move the slide.
The oil flow is controlled by two different solenoid valves 'A' and 'B', according to inputs from the unit controller. The
solenoids are normally-closed (NC) and they open when powered.
During the compressor operation, the valve position is controlled by the pressure inside the cylinder.
In the EWYD-BZ- heat pump, the unloading slide is only used to keep the compressor at minimum load upon start-up.
This, together with a start-up at reduced speed, prevents the compressor from taking in liquid, which could damage it,
even under extremely severe conditions such as when the operating mode is changed from chiller to heat pump or vice
versa.

Figure 24 - Capacity control mechanism for Fr3100 compressor

1 Oil supply
2 Oil vent to suction
3 Unload
4 Load
5 Slide
6 Spring
7 Discharge pressure acts on this side of piston
B
1
NC
3
7
A
2
NC
4
5 6
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