Filter
Top Products
80
If the OAT is between DXLOCK and 68_F (DXLOCK <
OAT < 68_F) and additional cooling is required, the
economizer will close the to minimum position for three
minutes, the economizer integrator will then be reset to 0
and begin modulating to maintain the SASP after the stage
has been energized for about 90 seconds. This will allow
the economizer to calculate a new ECONSR that takes
into account the cooling effect that has just been turned on
and not return to the value require before the cooling was
added. This will pre vent the economizer from causing
premature off cycles of compressors while maintaining the
low SAT temperature setpoint for the number of sta ges
active. In addition to preventing compressor short cycling,
by using return air acr oss the evaporator coil just after the
compressor has started allows for increased refrigerant
flow rates providing for better oil return of any oil washed
out during compressor start--up.
If the OAT > 68_F and OAT < SPT and the number of DX
stages requested is > 0 by the staging algorithm, then
ECONSR is set to its minimum value 48_F and the
dampe r will go to 100% open.
If the Auxiliary Relay is configured for exhaust fan
(AUXOUT = 1) i n the CONFIG configuration table and
Continuous Power Exhaust (MODPE) is Enable in the
SERVICE configuration table, then the AUXO output
(HS3) will be energized whenever the PremierLink
controller is in the occupied mode. If the MODPE is
disabled then AUXO output will be energized based on
the Power Exhaust Setpoint (PES) in the SETPOINT
table.
Heating — The heat stages are controlled by the Heating
Control Loop, which is used to calculate the desired SAT
needed to satisfy the space. It will compare the SPT to the
Occupie d Heat Setpoint (OHSP) + the T56 sl ider offset
(STO) when occupied and the Unoc cupied Heat Setpoint
(UHSP -- Unoccupied Heating Deadband) if unoccupie d to
calculate a Staged Heat Submaster Reference (SHSR).
The heat staging algorithm compares the SHSR to the
actual SAT to calculate the required number of heating
stages to satisfy the load. This loop runs every 40 seconds.
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 Cool mode is not active and the time guard between
modes equals zero.
S Mode is occupied or the Temperature Compensated Start
or Heat mode is active.
S SPT reading is available and < (OHSP + STO).
S If it is unoccupied and the SPT < (UHSP -- Unoccupied
Heating Deadband). The indoor fan will be turn on by the
staging algorithm.
When all of the above conditions are met, the SHSR is
calculated and up to 3 stages of heat will turned on and off
to satisfy to maintain the SAT = SHSR. If any of the
above conditions are not met, the SHSR i s set to its
minimum value of 35_F.
The Staged Heat Submaster Reference (SHSR) is
calculated as follows:
SHSR = Heat ing PID function on (error) where error =
(OHSP + STO) -- Space Temperature
The Maximum SHSR is determined by the SATHI
configuration. If the supply-- a ir temperature exceeds the
SATHI configuration value, then the heat stages will turn
off. Heat staging will resume after a delay to allow the
supply--air temperature to drop below the SATHI value.
The maximum number of stages available is dependent on
the type of heat a nd the number of stages programmed in
the CONFIG and SERVICE configuration tables. Staging
will occur as follows for gas electric units, Carrier heat
pumps with a defrost board, or cooling units with electric
heat:
For Heating PID STAGES = 2
HEAT STAGES = 1 (50% capacity) -- e nergize HS1.
HEAT STAGES = 2 (100% capacity) -- e nergize HS2.
For Heating PID STAGES = 3 and AUXOUT = HS3
HEAT STAGES = 1 (33% capacity if) -- energize HS1
HEAT STAGES = 2 (66% capacity) -- energize HS2
HEAT STAGES = 3 (100% capacity) -- e nergize HS3
Staging will occur as follows For heat pump units with
AUXOUT configured as reversing valve:
For Heating PID STAGES = 2 and AUXOUT = Reversing
Valve Heat (the H3_EX_RV output will stay energized
until there is a cool demand) HEAT STAGES = 1 (50%
capacity) shall energize CMP1, CMP2, RVS.
HEAT STAGES = 2 (100% capacity) shall energize HS1
and HS2.
Heating PID STAGES = 3 and AUXOUT = R eversing
Valve Heat (the H3_EX_RV output will stay energized
until there is a cool demand)
HEAT STAGES = 1 (33% capacity if) shall energize
CMP1, CMP2, RVS
HEAT STAGES = 2 (66% capacity) shall energize HS1
HEAT STAGES = 3 (100% capacity) shall energize HS2
If AUXOUT is configured for Reversing Valve Cool, then
the H3_EX_RV contact will be deenergized when there is
a demand for heating. The heat stages will be cycled to
temper the SAT so that it will be between the SPT and the
SPT + 10_F (SPT < SAT < (SPT + 10_F)) if:
S the number of heat stages calculated is zero
S the OAT < 55_F
S an IAQ sensor is installed
S the IAQ Minimum Damper Position > minimum damper
position
S and the SAT < SPT --10_F.
48TC