13
During Unoccupied period with demand, the control will
energize the fan contactor when demand is sensed. After fan
status is confirmed, operating routines will commence. When
demand is removed, routines will end and fan will shut off.
Sequence of Operation (CV, Automatic Fan)
— The fan will
be turned OFF during an Occupied period when there is no de-
mand for heating or cooling operation. When demand is
sensed, the control will energize fan contactor and fan status
will be confirmed. When demand is removed, routines will ter-
minate and fan will be shut off.
Configuration
— To configure the Fan Operation Type, enter
the Service function. Log on, if required. Press to enter
the User Configuration subfunction. Scroll down to Fan Mode
(FANM). Select the desired mode (Continuous = 1, Auto = 0),
by pressing or and . Log off when completed. See
Table 9.
COOLING — The cooling control loop is used to calculate
the desired supply-air temperature needed to satisfy the space
temperature (CV) or the supply air set point (VAV). The calcu-
lated CCSR is then used by the capacity algorithm (cooling
submaster loop) to control the required number of cooling stag-
es. See Table 10 for cooling control operation definitions.
Occupied/Unoccupied Cooling Modes
NOTE: Occupied Cooling Mode is 31. Unoccupied Cooling
Mode is 24.
The Cooling Control routine determines the staging of the
available compressors and unloaders to maintain space comfort
conditions. Cooling cycle is available during the Occupied pe-
riod, during Optimal Start routine, and during the Unoccupied
period. Cooling Control may be overridden by Dehumidifica-
tion mode (if enabled) when conditions warrant.
For full VAV operation, a T-55 space Temperature sensor is
required (factory-supplied, field-installed). For CV operation, a
Space Sensor (T-55 [factory-supplied, field-installed] or T-56
[field-supplied, field-installed]) is required.
Sequence of Operation, Occupied Cooling (VAV) — The econ-
omizer cycle must not be permitted or, if permitted, the out-
door air damper position must be open to 90% or higher. For
VAV operation the supply fan must be ON for cooling control
to operate and the unit must not be in Heating mode. The Mas-
ter Loop will survey occupancy status, SASP and any SAT
Reset command, then issue CCSR to Cooling Submaster Loop
(CSL). The CSL surveys actual SAT, then calculates number
of capacity stages required to produce the CCSR leaving
the unit. Stages of cooling capacity are initiated. The time
delay between stages in increasing demand is 90 seconds. As
actual SAT approaches CCSR value, stages are released. Mini-
mum time delay between stages on decreasing demand is
90 seconds.
NOTE: Demand for heating has priority when the control
senses a demand for heating, and Master Loop will either ter-
minate existing or prevent initiation of Cooling Cycle by issu-
ing a CCSR at the maximum limit. This will cause CSL to
select zero stages of cooling capacity.
Sequence of Operation, Occupied Cooling (CV) — The econo-
mizer cycle must not be permitted or, if permitted, the out-
door air damper position must be open to 90% or higher. The
supply fan must be ON for cooling control to operate. The
Master Loop will survey Space Temp and Space Temp Offset
inputs, then calculate CCSR value. The CSL surveys actual
SAT, then calculates number of capacity stages required to sat-
isfy space load. Stages of cooling capacity are initiated. (From
zero stages, there will be a 1.5 to 3 minute delay before first
stage is initiated.)
Unoccupied Cooling —The Unoccupied Cooling function is
similar to Occupied Cooling except for the following: the sup-
ply fan will be OFF as demand is initiated, the Master Loop
will start Supply Fan and fan status must be proved as ON, the
control set point will be the Unoccupied Cooling set point
(UCSP), and at the end of the cooling cycle, the supply fan will
be turned OFF.
Configure Cooling Set Points
— To configure cooling set
points, enter the Set Point function and the Set Point subfunc-
tion by pressing and . To select the Occupied Cooling
set point, scroll down to OCSP. The current set point value will
be displayed. The default is 78 F. The range of acceptable val-
ues is 55 to 80 F. To change the set point, press the numbers of
the new set point (example: ) and then press .
To select the Unoccupied Cooling set point, scroll down to
UCSP. The current set point value will be displayed. The de-
fault is 90 F. The range of acceptable values is 75 to 95 F. To
change the set point, press the numbers of the new set point
(example: ) and then press .
To select the Supply Air Temperature set point, scroll down
to SASP. The current set point value will be displayed. The de-
fault is 55 F. The range of acceptable values is 45 to 70 F. To
change the set point, press the numbers of the new set point
(example: ) and then press . See Table 11.
Cooling Algorithms
VAV: CCSR = MSAS = SASP + RESET
CV: CCSR = PID function on (Demand term)
where (Demand term) = OCSP + STO - SPT
Overrides
First Stage and Slow Change Override — The first stage over-
ride reduces cycling on the first stage of capacity. The slow
change override prevents the addition or subtraction of another
stage of capacity if the SAT is close to the set point and gradu-
ally moving towards the set point.
Low Temperature Override — The low temperature override
function protects against rapid load decreases by removing a
stage every 30 seconds when required, based on temperature
and the temperature rate of change.
High Temperature Override — The high temperature override
function protects against rapid load increases by adding a stage
once every 60 seconds as required, based on temperature and
temperature rate of change.
Table 8 — Configuring STANDBY OFF (“Run”)/STANDBY ON
ENTER
ENTER
ENTER
ENTER
DESCRIPTION HOW TO CONFIGURE SET POINT RANGE
Exit STANDBY (Place in ‘‘Run’’)
STBY
Select or ,
Display: STBY NO
Enter STANDBY
STBY
Select ,
Display: STBY YES
CLEAR
ENTER
ENTER
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