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T7351 COMMERCIAL PROGRAMMABLE THERMOSTAT
17 63-2666—03
Table 9. Default Auxiliary Relay Operations.
a
Simple dehumidification uses a normally closed contact. The relay is closed when humidity is below the high limit. When the
humidity is above the high limit, the contact is open.
Dehumidification
There are five methods through which the T7351 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.
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 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 cooling
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
T7351 maintains the proper setpoint by running the heat at the
same time.
IMPORTANT
At times during Reheat dehumidification, the T7351
operates heating and the cooling simultaneously. 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.
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. The default value is 2
degrees.
Though this may not technically reduce RH, 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, 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:
— 5% 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 10.
Heat Pump or
Conventional
Contact Not Used as
Heat or Cool Stage Contact Configuration of Contact Not Used as Stage
Heat Pump Y3 Simple
Dehumidification
a
Simple
Dehumidification
a
Time of Day Time of Day
W2 not aux heat Economizer Time of Day Economizer Economizer
Conventional W3 not Simple
Dehumidification
a
Simple
Dehumidification
a
Simple
Dehumidification
a
Time of Day
Y3 not (W3 not) Economizer Time of Day Time of Day Economizer
Y3 not (W3 used) Simple
Dehumidification
a
Simple
Dehumidification
a
Simple
Dehumidification
a
Time of Day
Auxiliary Contact Configuration Time of Day Economizer Hot Gas Bypass
Dehumidification
Simple
Dehumidification
a