Dehumidification (T7350D,H,M); Control Through Cooling; Options Utilizing Auxiliary Output; Hot Gas Bypass Dehumidification Logic - Honeywell T7350 Installation Instructions Manual

T7350 COMMERCIAL PROGRAMMABLE THERMOSTAT

DEHUMIDIFICATION (T7350D,H,M)

There are five methods through which the T7350 can
control for dehumidification. Three of them modify the
control algorithm, thus providing limited dehumidification
through cooling. The other two use the auxiliary output to
control another device.
IMPORTANT
Configurable only with a PDA.
NOTE: The dehumidification high limit can be set within
the range of 10 to 90 percent relative humidity.

Control Through Cooling

Configure using some combination of the following:
— Minimum On.
— Reheat.
— Reset.
NOTES:
— These methods operate only during cooling.
— Selecting both Reheat and Reset options can
cause frequent setpoint adjustments. This
selection is not recommended.
Min. ON Time
Dehumidifies by increasing the compressor minimum on
time (normally 3 minutes) by a programmable amount.
This is useful with oversized systems in that it forces the
coils to cool to a point where dehumidification can occur.
NOTES:
— Can force wider temperature swings by cool-
ing when setpoint control does not require it.
— The minimum on time can be set within the
range of 5 to 15 minutes.
— Hysteresis and a minimum timer are used to
ensure this behavior does not change with
every equipment cycle.
Reheat
Dehumidifies by operating cooling during typical off time.
The T7350 maintains the proper setpoint by running the
heat at the same time.
IMPORTANT
At times during Reheat dehumidification, the
T7350 operates heating and the cooling simulta-
neously. This is normal.
NOTES:
— The heat stage never energizes during
Reheat if more than one cool stage is on.
— Reheat mode cannot occur during heating.
— The T7350M does not support the Reheat
method.
62-0195—04
Reset Temp SetPt
The room temperature set point resets to a specified
number of degrees below the actual set point when room
relative humidity (RH) rises above humidity high limit set
point.
Though this may not technically reduce relative humidity
in the room, it reduces the dew point to provide the
customer with a sense of comfort due to a lower
temperature setting in the room.
As long as RH stays above humidity high limit set point,
this set point is maintained.
NOTE: Hysteresis and a minimum timer prevent the set
point from short interval alternation (between
standard and reset set points).

Options Utilizing Auxiliary Output

There are two dehumidification options that utilize the
auxiliary output. They are:
— Simple Dehumidification.
— Hot Gas Bypass Dehumidification.
Simple Dehumid(ification)
The auxiliary output:
— Energizes when RH rises above humidity high limit.
— De-energizes when RH drops below humidity high
limit.
NOTES:
— Hysteresis and a minimum timer prevent
short cycling of this output.
— Unlike Dehumid Hot Gas BP the relay
remains energized during calls for multiple
cooling stages.
Dehumid Hot Gas BP
The auxiliary output operates as shown in Table 5.
Table 5. Hot Gas Bypass Dehumidification Logic.
Humidity Cooling Stages Active Auxiliary Output
High more than one
High one or less
Low more than one
Low one or less
Auxiliary output during call for multiple cooling stages for
two reasons:
1. This method assumes that the cooling provides
dehumidification.
2. Multiple cooling stages probably provide necessary
dehumidification.
NOTE: Hysteresis and a minimum timer prevent short
cycling of this output.
14
De-energized
Energized
De-energized
De-energized