Dehumidification - Commercial - Honeywell Home THX9321 Prestige 2.0 Manual

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THX9321 PRESTIGE 2.0 AND THX9421 PRESTIGE
Fig. 238.

Dehumidification - Commercial

The thermostat reads the indoor humidity level and allows
the user to set a dehumidification setting. The thermostat
controls the humidity level using the cooling system or a
dehumidifier.
If humidification and dehumidification are setup to operate
in the same system mode (Heat, Cool, Off) and you are
sensing humidity from one location, the thermostat will
automatically enforce a 15% deadband between the
humidification and dehumidification settings. The
thermostat will automatically switch between
humidification and dehumidification to maintain the
desired humidity level.
If humidification and dehumidification are setup to operate
in the same system mode (Heat, Cool, Off) and you are
sensing humidity from two different locations using a
remote wireless indoor sensor (for example, main level and
crawl space), the thermostat will allow humidification and
dehumidification to operate at the same time, and there is
no deadband between humidification and
dehumidification settings.
Dehumidification Equipment Options: (ISU 9000)
• A/C with Low Speed Fan
• A/C with High Speed Fan
• Hot Gas Bypass
• Dehumidifier
NOTE: Hot Gas Bypass - During a call for dehumidifica-
tion, the cooling capacity will be used to remove
more latent heat than sensible heat. The operation
of Hot Gas Bypass varies by equipment. For more
details, contact the equipment manufacturer.
68-0311—08
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IAQ WITH EIM
Dehumidification Using the Cooling
System
Dehumidification using A/C with Low Speed Fan, A/C with
High Speed Fan or Hot Gas Bypass, has the following
methods of dehumidification control (ISU 9080):
Basic: This option uses the cooling system to reach the
desired humidity level. Minimum On Time, High Humidity
Comfort Reset and Reheat are not used with this method.
This setting is commonly used if your dehumidification
equipment is Hot Gas Bypass.
Minimum On Time (ISU 9090): This option ensures that the
compressor runs long enough to effectively reduce
humidity when the cooling equipment is cycled on. The
compressor will run for the minimum "on time" you set until
the desired humidity level is reached.
High Humidity Comfort Reset (ISU 9100): This option uses
the cooling system to lower the temperature up to 5° F
below the current cool setpoint until the desired humidity
is reached. The high humidity comfort range is from 1° to
5° F.
High Humidity Comfort Reset with Minimum On Time (ISU
9090 and 9100): This method uses both options above to
reduce humidity while maintaining a comfortable
temperature.
Reheat (ISU 9080): This option allows heating to run during
dehumidification to help maintain a comfortable
temperature. If only cooling stage 1 is used, during the "off"
cycle, both cooling and heating run at the same time as
needed to dehumidify without overcooling. This option
cannot be used in the Heat mode. This option is effective
only if using a system with the A-Coil located before the
heating coil (heat exchanger). This feature requires a
conventional forced air heating system (gas, oil, or electric)
in the application.
NOTE: Reheat can be used on heat pump applications
that have a forced air backup heat source (gas, oil,
or electric). The thermostat will turn on the first
stage of forced air backup heat during Reheat.
NOTE: Reheat can be used on systems where the A-Coil is
located after the heating coil (heat exchanger), but
it is not effective at removing humidity.
Reheat with Minimum On Time (ISU 9080 and 9090): This
method uses both Reheat and Minimum On Time options
above to reach the desired humidity level.
108
Fig. 239.