45
S Whenever the Supply Fan Relay point is forced On in the
STATUS01 points display table
The fan will also continue to run as long as compressors
are on when transitioning from occupied to unoccupied
with the exception of Fire Shutdown mode. If the Fire
Shutdown input point is cl ose d or forced in the
STATUS01 points di splay table, the fan will be shutdown
immediately regardless of the occupancy state or demand.
The PremierLink controller has an optional Supply Fan
Status input to provide proof of airflow. If this is enabled,
the point will look for a contact closure whene ver the
Supply Fan Relay is on. If the input is not enabled, then it
will always be the same state as the Supply Fan Relay.
The cooling, economizer and heating routines will use t his
input point for fan status.
Cooling — The c ompressors are controlled by the Cooling
Control Loop that is used to calculate the desired SAT
needed to satisfy the space. It will compare the SPT to the
Occupie d Cool Setpoint (OCSP) + the T56 slider offset
(STO) when occupied and the Unoccupied Cool Setpoint
(UCSP + Unoccupied Cooling Deadband) if unoccupie d
to calculate a Cooling Submaster Reference (CCSR) that
is then used by the staging algorithm (Cooling submaster
loop) to calculate the required number of cooling stages.
The economizer, if available, will be used as the first
stage of cooling in addition to the compressors. This loop
runs every minute. The following conditions must be met
in order for this algorithm to run:
S indoor fan has been ON for at least 30 seconds
S heat mode is not active and the time guard between
modes equals zero.
S mode is occupied or the Temperature Compensated Start
or Cool mode is active
S SPT reading is available and > (OCSP + STO)
S If m ode i s unocc upied and the SPT > (UCSP +
Unoccupie d Cooling Deadband). The indoor fan will be
turned on by the staging algorithm.
S OAT > DXLOCK or OAT DX Lockout is disabled
If all of the above conditions are met, the CCSR will be
calculated, otherwise it is set to its maximum value and
DX stages is set to 0. If only the last condition is not true
and an economizer is available, it will be used to cool the
space.
The submaster loop uses the CCSR compared to the actual
SAT to determine the required number of capacity stages
to satisfy the load. There is a programmable minimum
internal time delay of 3 to 5 minutes on and 2 to 5 minutes
off for the compressors t o prevent short cycling. The r e is
also a 3--minute time delay before bringing on the second
stage compressor. If the PremierLink controller is
configured for Heat Pump and AUXOUT is configured for
Reversing Valve Cool, the H3_EX_RV output will
energize 2 sec onds after the first compressor is energized
and stay energized until there is a demand for heat. If
AUXOUT is configured for Reversing Valve Heat, then
the H3_EX_RV contact will be deenergized when there is
a demand for cooling. An internal 5 to 10--minute
user--programmable time guard between modes prevents
rapid cycling between modes when used in a single zone
application. The Time Guard is lowered to 3 minutes
when Linkage is active to allow the 3Vt linkage
coordina tor to have better c ontrol of the Premier--Link
controller when used as the air source for the 3V control
system.
Table 13 indicates the number of stages available. The
staging algorithm looks at the number of stages available
based the number of cool stages configured in the
SERVICE configuration table. The algorithm will skip the
economizer if it is not availa ble and turn on a compressor.
Table 13 – Available Cooling Stages
NUMBER OF
STAGES
0
1
(ECONOMIZER*)
2 3
Compressor 1 Off Off On On
Compressor 2 Off Off Off On
* If conditions are suitable for economizer operation.
Any time the compressors are running, the PremierLink
controller will lockout the compressors if the SAT
becomes too low. These user configurable settings are
found in the SERVICE configuration table:
Compressor 1 Lockout at SAT < SATLO1 (50 to 65_F)
(default is 55_F)
Compressor 2 Lockout at SAT < SATLO2 (45 to 55_F)
(default is 50_F)
After a c ompressor is locked out, it may be started again
after a normal time--guard period and the supply air
temperature has increased at least 8_F above the lockout
setpoint.
Dehumidification — The PremierLink controller will
provide occupied and unoccupied dehumidification
control when AUXOUT = 5 in the CONFIG table and is
installed on HVAC units that are equipped with additional
controls and accessories to accomplish this function. This
function also requires a space relative humidity sensor be
installed on the OAQ/ IRH input.
When in the occupied mode and the indoor relative
humidity is greater then the Occupied High Humidity
setpoint, then the H3_EX_RV output point will be
energized. When in the unoccupied mode and indoor
relative humidity is greater then the Unoccupied High
Humidity setpoint, then the H3_EX_RV output point and
supply fan output will be energized. There is a fixed 5%
hysteresis that the indoor re lative humidity must drop
below the active setpoint to end the dehumidification
mode and deenergize the H3_EX_RV output. If the
PremierLink controller is in the unoccupied mode, then
the fan relay will deenergize if there is no other mode
requiring to the fan to be on. This function will not
energize mec hanical cooling as a result of the indoor
relative humidity exceeding either setpoint.
A high humidity alarm will be generated if the indoor
relative humidity exceeds the high humidity setpoint by
the amount configured in the Control Humidity Hysteresis
in the ALARMS table for 20 minutes. The alarm will
50TC
