Carrier 50TCA04-A07 - Manual (Page 47)

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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 and 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) -- energize HS1.
HEAT STAGES = 2 (100% capacity) -- energize 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) -- energize 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 = Reversing
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.
There is also a SAT tempering routine that will act as SAT
low limit safety to prevent the SAT from becoming too
cold should the economizer fail to close. One stage of
heating will be energized if it is not in the Cooling or Free
Cooling mode and the OAT is below 55_F and the SAT is
below 40_F. It will deenergize when the SAT > (SPT +
10_F).
Indoor Air Quality — If the optional indoor air quality
(IAQI) sensor is installed, the PremierLink controller will
maintain indoor air quality within the space at the user
configured differential setpoint (IAQD) in the CONFIG
configuration table. The setpoint is the difference between
the IAQI and an optional outdoor air quality sensor
(OAQ). If the OAQ is not present then a fixed value of
400 ppm is used. The actual space IAQ setpoint (IAQS) is
calculated as follows:
IAQS = IAQD + OAQ (OAQ = 400 ppm if not present)
As air quality within the space changes, the minimum
position of the economizer damper will be changed also
thus allowing more or less outdoor air into the space
depending on the relationship of the IAQI to the IAQS.
The IAQ algorithm runs every 30 seconds and calculates
IAQ minimum position value using a PID loop on the
IAQI deviation from the IAQS. The IAQ minimum
position is then compared against the user configured
minimum position (MDP) and the greatest value becomes
the final minimum damper position (IQMP). If the
calculated IAQ minimum position is greater than the IAQ
maximum damper position (IAQMAXP) decision in the
SERVICE configuration table, then it will be clamped to
IAQMAXP value.
If IAQ is configured for low priority, the positioning of
the economizer damper can be overridden by comfort
requirements. If the SPT > OCSP + 2.5 or the SPT <
OHSP -- 2.5 then IAQ minimum position becomes 0 and
the IQMP = MDP. The IAQ mode will resume when the
SPT ≤ OCSP + 1.0 and SPT ≥ OHSP -- 1.0.
If IAQ is configured for high priority and the OAT < 55_F
and the SAT < (SPT -- 10_F), the algorithm will enable the
heat stages to maintain the SAT between the SPT and the
SPT + 10_F.
IAQ Pre--Occupancy Purge — This function is designed to
purge the space of airborne contaminants that may have
accumulated 2 hours prior to the beginning of the next
occupied period. The maximum damper position that will
be used is temperature compensated for cold whether
conditions and can be pre--empted by Temperature
Compensated Start function. For pre--occupancy to occur,
the following conditions must be met:
S IAQ Pre--Occupancy Purge option is enabled in the
CONFIG configuration table
S Unit is in the unoccupied state
S Current Time is valid
S Next Occupied Time is valid
S Time is within 2 hours of next Occupied period
S Time is within Purge Duration (user--defined 5 to 60
minutes in the CONFIG configuration table)
S OAT Reading is available
If all of the above conditions are met, the economizer
damper IQMP is temporarily overridden by the
pre--occupancy damper position (PURGEMP). The
PURGEMP will be set to one of the following conditions
based on atmospheric conditions and the space
temperature:
S If the OAT ≥ NTLO (Unoccupied OAT Lockout
Temperature) and OAT < 65_F and OAT is less than or
50TC