Unit installation

18
value is below the Space RH Setpoint (RH.SP) minus the Space
RH Deadband (Setpoints →RH.DB), then dehumidification is no
longer needed. If the unit is configured for space sensor control
(Configuration →UNIT →U.CTL = 3), then the setpoint Dehum
Heat SP Deadband (Setpoints →RH.HB) applies. This
configuration sets the offset above the heating set point at which a
unit in dehum mode will turn off. This is a protection against over
cooling the space and causing a heat demand. There are three types
of dehum control set by the configuration Dehum Control Type
(Configuration →COOL →DHUM). Dehum Control is factory
defaulted to 0 which is No Control meaning that any dehum
demand is ignored.
NOTE: When there is a dehumidification demand, the economizer
damper position is limited to its minimum damper position
(Operating Mode →ECON →EC.MP).
Max Dehum (DHUM = 1)
When the Dehum Control Type (DHUM) is set to (1) Max dehum,
the control will try to satisfy the dehum demand. The Fan
Transition Time (FTT) will not be utilized nor the Supply Air
Upper Level (SAT.U). The Supply Air Lower Level (SAT.L) limit
will be honored while running the cooling stages. Fan Low
Suction (FLSU) will be handled per below.
With only a dehum demand, the control will start with 1
st
stage of
cooling at the Supply Fan Speed 1 (F.SP1). When stage 2 is
available it too will be requested leaving the fan at F.SP1. If the
Sat. Suction Temp A (SST.A) falls below the Fan Low Suction
Temp (FLSU) for one minute the fan will step up to Supply Fan
Speed 2 (F.SP2) for one minute. If SST.A still falls below FLSU
for one minute the fan will run at Supply Fan Speed 3 (F.SP3). If
the low suction still occurs, the second cooling stage will be
removed and the fan set back to F.SP1. If the low suction still
persists, then the fan will run at F.SP2 until the low suction alarm
trips out the circuit or the dehum call is satisfied.
With a dehum call and 1 stage of cooling being requested, the
control will run 1 stage of cooling at Supply Fan Speed 1 (F.SP1).
If the Sat. Suction Temp A (SST.A) falls below the Fan Low
Suction Temp (FLSU) for one minute the fan will step the fan to
F.SP2, if it continues, the fan will ramp to Supply Fan Maximum
Speed (FS.MX).
If dehum and max cooling is being requested, the control will run
both cooling stages at Supply Fan Speed 2 (F.SP2). Fan Low
Suction Temp (FLSU) will follow normal cooling operation.
Max Comfort (DHUM = 2)
When the Dehum Control Type is set to (2) Max Comfort, the
control will try to satisfy the demand while minimizing the cold air
dump. The Fan Transition Time (FTT) will not be utilized nor the
Supply Air Upper Level (SAT.U). The Supply Air Lower Level
(SAT.L) limit will be honored while running the cooling stages.
Fan Low Suction (FLSU) will be handled per below.
With only a dehum demand, the control will run 1 stage of cooling
at Supply Fan Speed 1 (F.SP1). If Supply Air Temperature (SAT)
falls below the Comfort SAT Setpoint (Setpoints →CCSP),thefan
speed will be raised to Supply Fan Speed 2 (F.SP2) for one minute
and so on up until Supply Fan Maximum Speed (FS.MX) is
reached or the SAT raises above the Comfort SAT Setpoint
(CCSP). If running FS.MX for one minute and the SAT is still
lower than the comfort setting, the cooling stage will be removed
for 10 min before trying again. Fan Low Suction Temp (FLSU)
will not be honored however the circuit will be allowed to trip on
low suction alarm.
With a dehum call and 1 stage of cooling being requested, the
control will run 1 stage of cooling at Supply Fan Speed 1 (F.SP1).
If the SAT falls below CCSP then the fan will raise one speed
every minute until Supply Fan Speed 3 (F.SP3) or SAT rises above
the CCSP. If SAT stays above CCSP plus 5 degrees the control
will be allowed to run 2
nd
stage of cooling. If the Sat. Suction
Temp A (SST.A) falls below the Fan Low Suction Temp (FLSU)
for one minute the control will drop the request for the second
stage cooling. If SST.A then falls below FLSU for one minute, the
fan will ramp to Supply Fan Maximum Speed (FS.MX).
If dehum and max cooling is being requested, the control will run
both cooling stages at Supply Fan Speed 2 (F.SP2). If the SAT
falls below CCSP then the fan will raise one speed every minute
until Supply Fan Maximum Speed (FS.MX) or SAT raises above
the CCSP. Fan Low Suction Temp (FLSU) will follow normal
cooling operation.
Heating Operation
The 48/50LC unit’s heating operation consists of: demand and
mode determination, staging request to satisfy the demand, and
handling a request with the unit’s resources. These resources can be
gas heat or electric heat. This section covers both gas heat units and
electric heat units. The Type of Heat Installed (Configuration
→HEAT →HT.TY) configuration will be factory set to 1 for gas
units, 2 for electric heat units with heaters installed, and 0 for
electric heat units without heat installed. In general, the unit enters
a heating mode based on a demand, decides how to satisfy the
demand, executes its plan, and then leaves the heating mode.
Supply-Air Temperature Sensor (SAT)
The SAT Heat Mode Sensing (Configuration
→HEAT→SAT→SAT.H) informs the unit that the supply air
sensor has been relocated downstream of the heat section. This
configuration affects the Supply Air Temperature (Temperatures
→AIR.T →SAT) value displayed as listed below.
When SAT.H = DSBL, the Supply Air Temperature
(Temperatures →AIR.T →SAT) value on the Scrolling Marquee
and the CCN tables will be forced to zero when heat outputs come
ON and for 5 minutes after. The default Supply Air Temperature
location is at the fan inlet, upstream of the heat section.
When SAT.H = ENBL, the Supply Air Temperature
(Temperatures →AIR.T →SAT) sensor reading is displayed at the
Scrolling Marquee and the CCN tables during heating mode. This
setting should only be used if the original SAT sensor wires are
removed from the field connection terminal board and replaced by
an accessory SAT sensor located in the supply duct downstream of
the heat section. There are then two supply air temperature limits
that become active, the Maximum SAT Lower Level
(Configuration →HEAT →SAT →SAM.L) the Maximum SAT
Upper Level (Configuration →HEAT →SAT →SAM.U).Any
time the supply air temperature rises above SAM.L the heat staging
will be limited to what is currently on and no additional stages can
be added until the supply air temperature falls back below SAM.L.
If the supply air temperature rises above SAM.U, then heating will
be reduced by removing a heat stage. That stage cannot be added
again until the Supply Air Temperature falls below SAM.L. If the
supply air temperature stays above SAM.U, then another stage will
be removed after the Heat Stage Decrease Time (Configuration
→HEAT →H.DEC). If SAM.L and SAM.U are configured so that
they are close together, the last stage of heat might cycle rapidly,
slowed only by its minimum on and off-time requirements.
Indoor Fan Control
On direct drive fan units the fan will follow simple control. With
any heating stages gas or electric, the fan will run high fan speed.
On belt drive VFD fan units the fan will always run at Supply Fan
Maximum Speed (FS.MX) during heat mode.
Heating Mode Control
The heating HVAC mode (Run Status →MODE →HVAC=4)
represents both types of heating (gas or electric) under all types of
control. For the unit to be allowed to enter the heat mode, heat
must be enabled (HT.TY = 1 or 2), and the Outdoor Air
Temperature (Temperatures →AIR.T →OAT) must be less than
the Heating Lockout Temp (Configuration →HEAT →HT.LO).
Heat OAT Lockout (Run Status →MODE →H.LOC) displays
when heat is locked out on outdoor temperature and therefore
cannot allow heat mode. The control will display if it is ok to select
the heating mode (Operating Modes →HEAT →OK.HT= Yes).
48/50LC