Electric Reheat Dehumidification Operation; Unit Disable Option; Figure 64 Dehumidification Control (°F); Table 12 Cooling Capacity Limitation - Bard MEGA-TEC W180B Service Instructions Manual

Electric Reheat Dehumidification Operation

The unit will utilize electric reheat dehumidification
when it receives an active dehumidification call from
the LC6000 supervisory controller. During the active
dehumidification call, the unit status message will show
"Active Dehum". An LC6000 equipped with and indoor
humidity sensor is required to utilize dehumidification.
On a call for electric reheat dehumidification, the
unit return air sensor will control the compressor and
heating element operation based on the supervisory
control setpoints. If the space temperature, based on
the sensor attached to the supervisory control, reaches
the cooling or heating setpoint, the dehumidification
call is overridden until the cooling or heating call is
satisfied. If communication is lost with the supervisory
controller during a dehumidification call, the electric
reheat function at the unit is lost and the unit will
operate in orphan mode.
During a call for electric reheat, the wall unit will
energize the compressor and the electric reheat coil
will be energized to extend the run time of the cooling
cycle, mitigating the cooling done by the compressor.
If/when the temperature falls to 2° above heating
setpoint, the compressor will be disabled until the
temperature is increased 2° below the cooling setpoint
and then the compressor will be re-energized (see
Figure 64). If/when the temperature reaches 4° below
the cooling setpoint, the electric heating elements will
be energized. The electric heating elements will be
disabled 2° below the cooling setpoint. The system will
continue the dehumidification process until either the
heating or cooling setpoint are reached again or the
requirement for dehumidification is no longer present.
A call for electric dehumidification is ignored if
there is a call for emergency vent, emergency cool or
emergency off.
For more information on dehumidification staging, see
latest version of LC6000 Service Instructions manual
2100-669.
Cool
Reheat
58
FIGURE 64
Dehumidification Control (°F)
59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79

Unit Disable Option

The wall-mount unit can be disabled by opening a dry
set of contacts connected to Input DI1 on the PLC
board. This feature can be used in addition to the
emergency off feature provided by the LC6000 to ensure
that the unit does not operate even when in orphan
mode. This feature is disabled by default and must be
enabled before the input will affect unit operation. When
the input detects open contacts, all unit operation will
stop and the dampers will close. This is an automatic
reset feature that will resume operation as soon as the
unit detects the contacts are closed again.
For applications that require the dampers to close
rapidly, the 24VAC power supplied to each actuator
should be removed so the actuator spring returns.
In normal operation, the dampers can take up to 2
minutes to close from fully open. When the 24VAC
power is removed from the actuator, the dampers will
close in under 30 seconds using the spring return on
the actuator.
Beginning with software version MGS1000.1.3.0,
output NO9 can be wired in series with the actuators
to utilize the spring return when unit disable or
emergency off are active on the controller.
NOTE: Alarm logging and trend logging will not be
available if power is removed from the controller
and unit offline alarms will be recorded on the
LC6000.
The unit disable input can be verified and adjusted by:
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 Digital Inputs;
press ENTER key.
5. Press UP or DOWN keys to scroll to Digital Ins C1-1.
6. Reference Disable row and En column (see Figure
65 on page 40).
7. Press ENTER key to scroll to Disable En value.
8. Press UP or DOWN key to change value.
9. Press ENTER key to scroll to Dir.
Manual 2100-749
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