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Operation

51 Liebert

iCOM

Figure 46 Dehumidification and reheat control bands

Low Limit 1 and Low Limit 2 are used to avoid overcooling a room during dehumidification. When a

low limit is reached, a compressor or the liquid cooling source that is used for dehumidification is

disabled. It is re-enabled when the return air temperature rises. The Low Limit 1 and 2 settings are

in the Service menu under Setpoints.

Low Limit 1: Low Limit 1 will disable one of two compressors for dehumidification. If only one

compressor is set for dehumidification, or if the dehumidification source is chilled water, this limit

will not be visible and will be inactive.

Low Limit 2: Low Limit 2 will disable both compressors for dehumidification. This limit will also

stop dehumidification in single compressor units and in chilled water units.

The limits become active when the return air temperature drops below a temperature value equal to

the sum of the temperature setpoint plus the value set on Low Limit 1 and 2 (the Low Limit settings

are negative values).

A dehumidification source is deactivated if the return air temperature drops below the Deactivation

Temperature, as in this example:

Temperature Setpoint: 70°F (21.1°C)

Low Limit Value: -7°F (-3.8°C)

Deactivation Temperature: 63°F (17.2°C)

NOTE

If a cooling unit is equipped with SCR reheat and the SCR Control Type parameter is set to

Tight mode, then Low Limit 2 will be ignored, see 3.5 - Temperature Control—Reheat.

Dehum Reheat Prop Band

-100%

-Temp

33% 33% 33%

Step 3 Step 2

Step 3 on

Step 3 off

Step 2 on

Step 2 off

Step 1 on

Step 1 off

Dehum/ Reheat

Setpoint

Heater

Deadband

Step 1