Heating Operation - Carrier 48LC 04 Controls, Start-Up, Operation And Troubleshooting

(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
nd
will be allowed to run 2 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
→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,
(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,
(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
(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.
Sensing (Configuration
the Supply Air Temperature
the Supply Air Temperature
Maximum SAT Lower Level
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).
Thermostat Control
For the unit to enter heating mode, three additional things must be
true: the indoor fan must be ok to use, the mode changeover time
guard must be expired, and there must be a heating demand (W1,
W2). The unit will remain in heating until the heating demand is
dropped or if any of the above conditions turn false. The heating
mode can not officially end until all heat stages are off and the IGC
fan request (IGC.F) is dropped.
Space Sensor Control
For the unit to enter heating mode, five things must be true: the
indoor fan must be ok to use, the mode changeover time guard
must be expired, the unit must have a valid space temperature, the
W1 jumper must be installed, and there must be a heating demand.
The unit will remain in heating for at least one minute and until the
demand is dropped or if any of the above conditions turn false. The
heating mode can not officially end until all heat stages are off and
the IGC fan request (IGC.F) is dropped.
Staging Control
Once the unit is in a heating mode, it must decide what the demand
is and how to satisfy. Based on the unit control configuration,
requested heating stages (Run Status →HEAT →REQ.H) will be
determined then passed to heat control to actually add the heating
stages.
Thermostat Control
There are two ways of requesting stages when thermostat control is
enabled, Traditional Thermostat control or Adaptive control.
Traditional Thermostat control is used if the Thermostat Control
Type (T.CTL) is set to 1, 2, or 3. Adaptive control is used if
Thermostat Control (T.CTL) is set for 0.
T.CTL = 0 (Adaptive Control)
Stage timers and supply air temperature limits apply when
determining the request for stages. The first request (REQ.C=1)
comes immediately when the W1 input is active. The Heat Stage
Increase Time (Configuration →HEAT →H.INC) or the Heat
Stage Decrease Time (Configuration →HEAT →H.DEC) has to
expire before another stage can be added or a stage can be
subtracted. If at any time the Supply-Air Temperature (SAT) falls
below the Maximum Supply Air Temperature Lower Level
(Configuration →HEAT →SAT →SAM.L), the requested stages
will not be allowed to increase. If at any time the SAT falls below
the Maximum Supply Air
(Configuration →HEAT →SAT →SAM.U), the requested stages
will be reduced by one without honoring H.DEC.
T.CTL = 1, 2 or 3 (Traditional thermostat control)
Stage timers and supply air temperature limits do not apply when
determining the request for stages. Request staging will follow the
thermostat inputs directly. W1 will request one stage. W2 will
request all stages.
Space Sensor Control
Space sensor staging control is an adaptive anticipation control that
weighs the actual space demand against the trend of that demand. It
also honors stage time guards and supply air limits. The demand
for heating in the space is displayed as the Heating Demand (Run
18
Temperature Upper Level