2
Specifications are subject to change without notice.
© 2019 Mitsubishi Electric US, Inc.
Contents
1. Control box component identification
2. Operating sequence
LAHK-1 Control Box Component Identification
Operating Sequence
Outdoor Unit in Cooling Mode
The LAHK-1 low ambient hood is designed to reduce
the airflow through the outdoor units as the ambient
temperature drops. This maintains the head pressure
at a level that will allow the system to perform at 100%
capacity down to -10
o
F outdoor temperature.
A thermistor mounted on the side of the unit senses
the outdoor temperature. As the outdoor temperature
drops, the resistance of the thermistor increases. The
thermistor is connected to the specially designed circuit
board and the resistance value from the thermistor is
converted to a DC voltage output within the circuit
board. This DC voltage output drives the damper
actuator to a predetermined position based on the
outdoor temperature.
The inverter driven fan motor will adjust the discharge
pressure based on system capacity demand. The
motor will speed up and force more air through the
damper if there is a higher system capacity demand, or
slow down if system capacity demand decreases.
Outdoor Unit in Heating Mode
Heating mode requires the damper be in the fully open
position to allow full airflow and maximum heating
capacity.
Heating mode automatically deactivates the kit through
an interlock relay. The coil for this relay is tied into the
reversing valve connection on the outdoor unit. When
the unit switches to heating mode, the reversing valve
is energized. This in-turn energizes the interlock relay.
When the relay is energized, the normally closed
contact opens. By opening this contact, the power to
the transformer and control board is interrupted, this
allows the damper to spring to the full open position.
Outdoor Unit in Defrost Mode
If the outdoor unit will be running in heating mode, a
defrost period is inevitable. During defrost the low
ambient controls see this as the unit operating in
cooling mode. If the outdoor temperature is below 50 F,
the damper will close to a position equal to that
required during the cooling cycle. Once the unit comes
back out of defrost and into heating mode, the damper
will again spring wide open for full airflow.
Operation Test
Outdoor unit must be in cooling mode
December 2013
© 2013 Mitsubishi Electric US, Inc.
2
Outdoor unit in cooling mode
The LAHN-1/LAHN-3 low ambient hood is designed to reduce the
airflow through the outdoor units as the ambient temperature drops.
This maintains the head pressure at a level that will allow the system
to perform at full capacity down to -10°F outdoor temperature.
A thermistor mounted on the side of the unit senses the outdoor
temperature. As the outdoor temperature drops, the resistance of
the thermistor increases. The thermistor is connected to the specially
designed circuit board and the resistance value from the thermistor
is converted to a DC voltage output within the circuit board. This DC
voltage output drives the damper actuator to a predetermined position
based on the outdoor temperature.
The inverter driven fan motor will adjust the discharge pressure based
on system capacity demand. The motor will speed up and force more
air through the damper if there is a higher system capacity demand,
or slow down if system capacity demand decreases.
Outdoor unit in heating mode
Heating mode requires the damper be in the fully open position to
allow full airflow and maximum heating capacity.
Heating mode automatically deactivates the kit through an interlock
relay. The coil for this relay is tied into the reversing valve connection
on the outdoor unit. When the unit switches to heating mode, the
reversing valve is energized. This in turn energizes the interlock relay.
When the relay is energized, the normally closed contact opens. By
opening this contact, the power to the transformer and control board is
interrupted, this allows the damper to spring to the full open position.
Outdoor unit in defrost mode
If the outdoor unit will be running in heating mode, a defrost period
is inevitable. During defrost the low ambient controls see this as the
unit operating in cooling mode. If the outdoor temperature is below
40°F, the damper will close to a position equal to that required during
the cooling cycle. Once the unit comes back out of defrost and into
heating mode, the damper will again spring wide open for full airflow.
Operation test
Outdoor unit must be in cooling mode.
All hoods and damper controls are tested at the factory before shipping.
To perform an operational test once the installation is complete, follow
the steps below. Please refer to the chart and table below for detailed
control logic.
Operation testing when the outdoor ambient is ABOVE 40°F
1. Turn on power to the outdoor unit.
1. Control box component identification .....................................
2
2. Operating sequence ...............................................................
2
3. Damper blade adjustment ......................................................
5
4. Damper actuator manual override .........................................
8
5. Parts list ..................................................................................
9
6. Wiring diagram .....................................................................10
