Emerson Liebert iCOM User Manual download pdf (Page 22)

Operation

3.2.2 Compressor Control

All compressorised PEX models operate two (2) stages of cooling. For single compressor models, a hot

gas bypass valve operates in conjunction with the compressor.

Compressor Proportional Bands

Two Single-Step Compressors —Two-Step

First single-step compressor, Cool 1, is started at 50% calculated output from the temperature propor-

tional band, and stopped at 0%. The second compressor, Cool 2, starts at 100% and stops at 50% (see

Figure 13).

One Compressor With Hot Gas Bypass (HGBP) —Two-Step

The compressor and HGBP valve, Cool 1, are started at 50% calculated output from the temperature

propotional band, and stopped at 0%. The HGBP valve de-energises, Cool 2, at 100% and re-energises

at 50%. (see Figure 13).

Figure 13 Two single-step compressors or one compressor with HGBP (two-step)

1/2 Proportional Band

Cool 1

Cool 2

Cool 1

Off

Cool 2

Off

+ 100%

Cooling

0% 

Cooling

Increasing Temperature

Temp Setpoint: 21

Proportional Band: 4

Deadband: 1

1/2 Deadband

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Emerson Liebert iCOM User Manual Page 22