Manual 2100-695C
Page
17 of 56
units. The supervisory controller will then calculate the
dehumidification demand based on how far above the
setpoint and how long the RH level has been above the
setpoint. The controller will then utilize all of the units
with active dehumidification capabilities to reduce
the indoor humidity level. The units will be staged on
based on the existing cooling rotation for the units in
the zone up to the maximum number of units allowed to
run. When in demand minimum compressor run time is
applicable, examples of demand are as follows:
With two units with dehumidification capabilities, Unit
1 in rotation will come on at 50% demand and Unit 2 in
rotation will come on at 100% demand. They will rotate
off in a reverse; Unit 2 will be off at 50% demand and
Unit 1 will be off at the dehumidification off setpoint.
With three units with dehumidification capabilities,
Unit 1 in rotation will come on at 33% demand, Unit 2
in rotation will come on at 67% demand and Unit 3 in
rotation will come on at 100% demand. They will rotate
off in reverse; Unit 3 will be off at 67% demand, Unit
2 will be off at 33% demand and Unit 1 will be off at
dehumidification off setpoint.
An active dehumidification sequence will run until
the space temperature falls to the heating setpoint or
increases to the cooling setpoint, or the dehumidification
off setpoint is reached. Refer to the specific unit
manual for active dehumidification sequence and space
temperature control.
The passive dehumidification setpoint must be lower
than the active dehumidification setpoint to ensure the
economizer is disabled during active dehumidification.
Availability for active dehumidification will be
determined by model number. Units with electric reheat,
mechanical dehumidification or cycling reheat will be
considered. The active dehumidification default setpoint
is 80% RH.
Cycling Dehumidification Operation
On a call for active dehumidification from the
supervisory control, the wall unit will enter cycling
dehumidification mode and economizer free cooling
operation will be discontinued during cycling reheat.
If at any time the unit receives a heat or cooling call
while in cycling dehumidification mode, the unit will
exit cycling dehumidification until the heating or
cooling call is satisfied.
During cycling dehumidification, the return air
sensor is used to determine operation of the cycling
dehumidification. When the unit enters cycling
dehumidification mode and the return temperature
is above 55°F, the unit compressor will come on
with a reduced blower speed. The blower speeds are
referenced in tables 5A, 5B, and 5C on page 21 as
Dehumidification Mode; these speeds are unit specific.
The unit will continue to operate in this fashion until
the return air temperature falls to 55°F at which time
the compressor will be deactivated. After a 5-10
second delay, the electric heat will energize and the
blower will go to rated speed for electric heat. The unit
will continue to utilize electric heat until the return
air temp rises to 2°F below the cooling setpoint and
then return to compressor operation with the blower at
dehumidification mode speed. If the unit enters cycling
dehumidification mode and the return air is below
55°F, the unit will begin the sequence with the heating
mode as described.
A call for cycling dehumidification is ignored if there
is a call for emergency vent, emergency cool or
emergency off.
NOTE:
This feature is dependent upon the LC6000
indoor humidity sensors and a command
from the LC to enter dehumidification mode.
See the latest revision of LC6000 Service
Instructions 2100-669 for adjustment of the
dehumidification setpoint and differentials.
Electronic Expansion Valve (EEV)
EEV Components
Electronic Expansion Valve
The electronic expansion valve is a stepper motor that
is controlled with a step output from the controller. The
valve is capable of 480 steps represented by a 0-100%
signal on the controller. The motor drives a needle valve
that regulates the flow of refrigerant.
EEV Instructions for Vacuum, Reclaim, Charge Unit
The electronic expansion valve moves to the 20% open
position when the unit is not actively cooling. The
valve may need to be manually positioned for service or
troubleshooting. The valve can be positioned by using a
menu override.
To manually override the valve:
NOTE:
The unit must be off to perform this override.
1. Press MENU key to go to the Main Menu screen.
2. Press UP or DOWN keys and ENTER key to enter
TECHNICIAN password 1313.
3. Press UP or DOWN keys to scroll to
I/O Config
;
press ENTER key.
4. Press UP or DOWN keys to scroll to
EEV Service
C15
.
5. Press ENTER key to scroll to
Enable
(see Figure 25
on page 18)
.
6. Press UP or DOWN key to change
Disable
to
Enable
.
7. Press ENTER key to scroll to
Position
.
8. Press UP or DOWN keys to adjust to the desired
value.
9. Press ENTER key to save.
