Liebert iCOM Microprocessor TM-10098 Manuel d'utilisateur télécharger pdf (Page 20)

iCOM

Control Training and Service Manual

temperature is at least 8°F below the return air temperature, or 3°F lower than the

return air temperature for two consecutive hours.

When the microprocessor decides that the return glycol fluid temperature is cold

enough the first cooling band is the modulating valve control method, and the

second band, added to the first band, is for the compressors as in the normal

2-Stage or 4-Stage control method. If the chilled glycol fluid temperature is not

cold enough the valve control band is replaced by the compressor band. If the

chilled glycol cooling capacity is reduced by a rise in the glycol fluid temperature,

the control band shrinks proportionally. This allows the compressor band to move

down as well. The following shows the Glycool operation at 100% capacity and

the Glycool at 50% capacity.

Glycool at 100% Capacity – No Dead Band

Temp Set Point: 70°

Proportional Band: 8°

70 71 72 73 74 75 76 77 78 79

Increasin

Temperature

Band 1 Gl

cool Valve Band 2 Compressors

Valve

Closed

100%

Open

Cool 1 On

Cool 2 On

Temp Set Point + (1/2 Proportional Band + 1/2 Proportional Band)

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 169 170

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Liebert iCOM Microprocessor TM-10098 Manuel d'utilisateur Page 20