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REHEAT MODE DIAGNOSTIC HELP
The status of reheat mode sensor inputs may be viewed within
the display INPUTS menu. The status of reheat mode outputs
may be viewed within the display OUTPUTS or RUN STA-
TUS MODE menu. Additional diagnostic help, including
status of circuit reheat temperature limit lockouts may be
viewed within the Humidi-MiZer sub-menu of the cooling
mode diagnostic table at RUN STATUS COOL DE-
HUM. The Service Test mode may be used to force the system
to operate Dehumidification mode (Hot Gas Reheat) and De-
hum/Mech Cooling mode (Subcooling), or to independently
operate the reheat valve control outputs.
The following forced operating states are available service test
operations for a Humidi-MiZer system equipped unit:
SERVICE TEST COOL TEST HUMIDIMIZER TEST
LEVEL
A value of “0” sets reheat control test to “Off.”
SERVICE TEST COOL TEST HUMIDIMIZER TEST
LEVEL
A value of “1” sets Humidi-MiZer control test to “Dehum/
Mech Cooling mode (Subcooling).”
SERVICE TEST COOL TEST HUMIDIMIZER TEST
LEVEL
A value of “2” sets Humidi-MiZer test to “Dehumidification
mode (Hot Gas Reheat).”
SERVICE TEST INDEPENDENTS LIQ DIVERT A
TEST
A value of “On” will turn on the 3-Way Liquid Diverter Valve
(LDV).
SERVICE TEST INDEPENDENTS REHEAT A TEST
A value of “On” will turn on the Reheat Discharge Valve
(RDV).
Indoor Fan Based Dehumidification
Belt drive units that are not factory configured for Humidi-
MiZer operation can be set for improved dehumidification op-
eration through fan based humidification (FBD), SETTINGS
UNIT CONFIGURATIONS COOLING FBD TYPE.
Units are factory defaulted to FBD TYPE = 0, which means
that any dehum demand is ignored. There are two fan based de-
humidification options: Max Comfort (FBD TYPE = 1) and
Max Dehumidification (FBD TYPE = 2). Fan based dehumidi-
fication requires the installation and configuration of either a
space relative humidity sensor or a relative humidity switch in-
put. The Space Humidity Switch configuration, SETTINGS
UNIT CONFIGURATIONS SWITCH INPUTS CON-
FIGS HUMSTAT CHANNEL, identifies the normally open
or normally closed status of this input at HIGH humidity. The
RH Sensor configuration, SETTINGS UNIT CONFIGU-
RATIONS ANALOG INPUTS CONFIGS SPRH SEN-
SOR CHANNEL, identifies the point on the MBB (Main Base
board) or the IOB (Input Output board) the sensor was wired
into.
MAX DEHUM
When the FBD Type is set to (2) Max Dehum, the control will
try to satisfy the dehumidification demand. When the unit re-
ceives a dehum demand, a PID control algorithm will modulate
the indoor fan while the compressor is running to maintain mini-
mum suction temperature (FBDH_SST). With a Y1 and dehum
demand, the unit will run the compressor unloaded (48/50LC04-
06) or will run the A1 compressor only (48/50LC07-26). With a
Y2 and dehum demand, the unit will run with the compressor at
full load (48/50LC04-06) or will run with the A2 compressor
only (48/50LC07-26). With a Y3 and dehum demand (48/
50LC07-26 only), the unit will run both compressors.
MAX COMFORT
When the FBD Type is set to (1) Max Comfort, the control will
try to satisfy the dehumidification demand and minimize cold air
dump. When the unit receives a dehum demand, a PID control
algorithm will modulate the indoor fan while the compressor is
running to maintain the minimum FBD supply air comfort set
point (FBDH_SAT) while also maintaining the minimum suc-
tion temperature (FBDH_SST). With a Y1 and dehum demand,
the unit will run the compressor unloaded (48/50LC04-06) or
will run the A1 compressor only (48/50LC07-26). With a Y2
and dehum demand, the unit will run with the compressor at full
load (48/50LC04-06) or will run with the A2 compressor only
(48/50LC07-26). With a Y3 and dehum demand (48/50LC07-26
only), the unit will run both compressors.
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
(UNIT TYPE OF HEAT) configuration will be factory set to 1
for gas units and 0 for electric heat units. 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.
HEATING MODE CONTROL
The heating HVAC mode (OPERATING MODE) has 3 differ-
ent operating sub modes (SUBMODE): HEATING, HEATING
PREVENTED, and SHUTTING HEAT OFF. These are all part
of a general heating mode and resemble the action heat mode is
taking at any given time. All types of heating are still per-
formed under the general heating function, and the expanded
text is for user reference only.
For the unit to be allowed to enter the heat mode, three things
must be true: the indoor fan must be okay to use, the mode
changeover time guard must be expired, 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 are false. The heating mode does not officially end
until all heat stages are off, the fan off delay has expired, and
the IGC fan request is dropped.
SUPPLY-AIR TEMPERATURE SENSOR (SAT) HEAT
MODE
The SAT Heat Mode Sensing (SAT DURING HEAT?) informs
the unit that the supply air sensor has been relocated down-
stream of the heat section. This configuration affects the Sup-
ply Air Temperature (SUPPLY AIR TEMP) value displayed as
listed below. SAT DURING HEAT? is enabled at the factory.
When SAT DURING HEAT? is disabled, the Supply Air Tem-
perature (SUPPLY AIR TEMP) value on the SystemVu™ dis-
play and the network will hold a zero when heat outputs come
ON and for 5 minutes after. The default SAT sensor location is
on the fan deck near the corner post.
When SAT DURING HEAT? is enabled, the Supply Air Tem-
perature (SUPPLY AIR TEMP) sensor reading is displayed at
the SystemVu controller and network during heating mode.
This setting should only be used if the original SAT sensor
wires are removed from the Main Base Board (MBB) and re-
placed by an accessory SAT sensor located in the supply duct
downstream of the heat section.
HEATING STAGING CONTROL
Once the unit is in a heating mode, it determines what the de-
mand is and how to satisfy it. Requested Heating Stages (REQ.
HEAT STAGES) will be determined, then passed to heat control
to actually add the heating stages. To request stages, the number
of heat stages (HEATING STAGE QTY) must be greater than
zero. As a gas unit this will be set in the factory; however,
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