Optional Humidi- -Mizer; Dehumidification System - Carrier 48LC Series Controls, Start-Up, Operation And Troubleshooting

Low Ambient Operation
Low ambient operation will be used when either of the 2
conditions is met: 1) OAT is less than low ambient temperature
(LOW AMBIENT TEMP) – 5_F or 2) OAT is less than low
ambient temperature (LOW AMBIENT TEMP) – 2.5_F and the
Saturated Discharge Temperature (CIR.A DIS. TEMP) is less than
92_F. The low ambient ODF control will manipulate ODF speed to
keep the discharge temp above 95_F. As OAT continues to drop,
ODF speed will continue to decrease, at certain point, the low
ambient control may decide to turn off ODFs and only control the
speed of the rest of the outdoor fans. If the discharge temp keeps on
decreasing, it may reach a point that all ODF fans will be turned
off. The ODFs will be turned on starting from the highest number
first, meaning the ODF1 will be the last one to shut off. The ODFs
are protected with a 45 second run time and a 60 second off time.
See Fig. 12 for the ODF arrangement. The lowest speed allowed to
run any ODF is determined by the outdoor fan Minimum Speed
Configuration (ODF MINIMUM SPEED).
NOTE: During ODF cycling all fans that are commanded on will
be at the same speed and the ones off will be at zero speed. The
motors will not be allowed to run different speeds at the same time.
When OAT rises above low ambient temperature (LOW AMBIENT
TEMP), ODF control will transition from low ambient to normal
operation. A period (5 min) is allowed for the ODF speed to ramp
from current position to one of the 4 discrete speed settings.
IMPORTANT: The low ambient temperature (LOW AMBIENT
TEMP) is default to 66 degrees and should not be changed unless
directed by authorized Carrier Personnel.

Optional Humidi- -MiZer

Units with the factory- -installed Humidi- -MiZer system option are
capable of providing
dehumidification as a variation of the normal cooling cycle. The
Humidi- -MiZer system option includes additional valves in the
liquid line and discharge line of each refrigerant circuit, a reheat
coil downstream of the evaporator, and variable- -speed control of all
the outdoor fans. The Humidi- -MiZer system equipped configuration
is factory set to Yes for Humidi- -MiZer system equipped units
(HUMIDIMIZER OK = YES). This enables Humidi- -MiZer system
operating modes and service test.
Humidi- -MiZer system operation requires the installation and
configuration of a relative humidity switch input or a space relative
humidity sensor. The HUMIDISTAT and SPRH leads are provided
with quick connects. The Space Humidity Switch configuration,
SETTINGS  UNIT CONFIGURATIONS  SWITCH INPUTS
CONFIGS  HUMSTAT CHANNEL identifies the normally open
or normally closed status of this input at high humidity. The Space
RH Sensor configuration,
CONFIGURATIONS  ANALOG INPUTS CONFIGS  SPRH
SENS CHANNEL, identifies to the channel number the sensor is
wired into.
Dehumidification Demand
When using a humidistat or switch input, the demand for
dehumidification is seen
(INPUTSSWITCH INPUTSHUMIDISTAT) being Low or
High. A low value means humidity level is good and a high value
means that dehumidification is needed.
When using an SPRH sensor, the demand is based on the Space
Humidity Sensor (INPUTSANALOG INPUTSSPRH) value
compared to the Space RH Setpoint (SETTINGSSPACE
SETPOINTSSPRH SETPOINT). If the Space Humidity Sensor
(SPRH) value is above the Space RH Setpoint (SPRH Setpoint), then
dehumidification is needed. If the Space Humidity Sensor (SPRH)
value is below the Space RH Setpoint (SPRH Setpoint) minus the
Space RH Deadband (SETTINGSUNIT CONFIGURATIONS
COOLINGSPRH DEADBAND), then dehumidification is no
longer needed.
R

Dehumidification System

multiple modes of improved
SETTINGS

as Space Humidity
NOTE: When there is a dehumidification demand, the economizer
damper position is limited to its minimum damper position.
Humidi- - MiZer System Modes
With Humidi- -MiZer system units there are two additional HVAC
modes available for the user: Dehumidification and Dehum/Mech
Cooling. Selection of the Dehum/Mech Cooling mode is
determined by the dehumidification demand and the cooling
demand. Table 11 shows the corresponding circuit mode and
output status for the different demand combinations.
Normal Cooling
For 48/50LC07- -26 units, refrigerant flows from the outdoor
condenser through the de- -energized 3- -Way Liquid Diverter Valve
(LDV) to the expansion device bypassing the reheat condenser
coil. The Reheat Discharge Valve (RDV) is closed. (See Fig. 14.)
Table 11 – Humidi- -MiZer System Control Modes - - Sizes 07- -26
DEMAND AND MODE
Circuit
Space
Cooling
Humidity
Demand
— –
Low No
Low Yes
High Yes
High No
For 48/50LC04- -06 units, refrigerant flows from the outdoor
condenser and is diverted at the energized Reheat Liquid Valve
(RLV) and flows through the de- -energized Cooling Liquid Valve
(CLV) to the expansion device bypassing the reheat condenser coil.
The RDV is closed.
Table 12 – Humidi- -MiZer System Control Modes - - Sizes 04- -06
DEMAND AND MODE
Circuit
Space
Cooling
Humidity
Demand
— –
Low No
Low Yes
UNIT
High Yes
High No
Dehum/Mech Cooling (Subcooling Mode)
Switch
This mode increases latent heat removal and decreases sensible
cooling compared to normal cooling. For 48/50LC07- -26 units,
refrigerant flows from the outdoor condenser, through the
energized 3- -Way Liquid Diverter Valve (LDV) and through the
reheat condenser coil to the expansion device. The Reheat
Discharge Valve (RDV) is closed. (See Fig. 16.)
For 48/50LC04- -06 units, refrigerant flows from the outdoor
condenser through the de- -energized Reheat Liquid Valve (RLV)
and through the reheat condenser coil to the expansion device. The
Reheat Discharge Valve (RDV) and Cooling Liquid (CLV) are
closed. (See Fig. 15.)
19
OUTPUTS 48/50LC 07--- 26 Valves
Circuit Circuit LDV Valve
Mode Compressor 3--- way
No power Off Off
Off Off Off
Cool On Off
Dehum/Mech
On On
Cooling
Dehum On On
OUTPUTS 48/50LC 04---06 Valves
Circuit Circuit RDL
Mode Compressor Valve
No Off
Off
power (closed)
Off
Off Off
(closed)
Off
Cool On
(closed)
Dehum/
Off
Mech On
(closed)
Cooling
On
Dehum On
(open)
RDV Valve
2--- way
Off
(closed)
Off
(closed)
Off
(closed)
Off
(closed)
On
(open)
RLV CLV
Valve Valve
Off Off
(open) (open)
Off Off
(open) (open)
Off Off
(closed) (open)
Off On
(open) (closed)
Off On
(open) (closed)