User manual

Operation
21
An automatic flush cycle occurs whenever the humidifier current draw equals or exceeds the current
set value. The make-up valve is energised for the bottle flush time duration. Refer Table 5. The
humidifier output is de-energised during the flush cycle and re-energised 5 seconds afterwards.
Should the humidifier current draw exceed the current set value by 50%, an alarm will be activated
(Humidifier High Amps) and the humidifier will be latched out.
In the event of a water under floor alarm, the humidifier operation will be latched out until 5 minutes
after the alarm is reset.
3.3.4 Dehumidification
The Dehumidification Enable parameter (Service Menu, Options Setup) allows for enabling/disabling
the dehumidification function.
A call for dehumidification is calculated in the same way as a cooling request. The components
(valves, compressors) will follow this dehumidification request as soon as it is higher than the request
for cooling.
Dehumidification Low Limit
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 dis-
abled. 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 com-
pressor 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:
Dehumidification Compressor Quantity
Under Factory Settings in the Advanced menu there is an item called Dehumidification With Comp.
For Liebert PEX units this item is set to 1. This setting determines which compressors are used for
dehumidification. It also determines if Low Limit 1 will be available and impacts how the reheats will
operate during dehumidification. The Dehumidification With Comp field is set when the cooling unit
is built and should not be adjusted without consulting the factory first. Table 6 outlines which Low
Limit settings will be available, based on the Dehumidification With Comp selection.
Temperature Setpoint: 22°C
Dehum Low Limit Value: -3°C
Deactivation Temperature: 19°C
NOTE
Dehumidification will be allowed to restart when the return temperature exceeds setpoint.
Table 6 Dehumidification With Comp settings
Available to Set Value Dehumidification With Comp Setting Default Setting On
Low Limit 2 only
[blank] (units without compressors) Chilled Water Liebert PEX
™
models
1 (Compressor 1 dehumidifies only) Compressorised Liebert PEX
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models