Mitsubishi Electric LAHN-1 Technical & Service Manual page 4

Circuit board
Confirm the thermistor is operating properly before troubleshooting
the circuit board.
Make sure the control board has 24 Volts AC when measured at the
24 VAC and the com terminals. If not, find the cause of voltage failure.
The circuit board is designed to convert the thermistor ohm input to
a 2 - 9.16 VDC output to control the position of the damper actuator.
Above 2 VDC output the actuator will start to move the damper toward
the closed position. At 9.16 VDC, the actuator will have moved 85
degrees and the damper will be approximately 95% closed. The
damper should never be 100% closed. The chart below includes the
various damper angles based on the different outdoor temperatures.
Measure the DC voltage output on the circuit board at com (-) and
the out (+) terminals. If the output doesn't match the thermistor input
The transformer is 208/230 – 24volt AC. For proper
ohms as shown below, replace the circuit board.
connections to the outdoor unit, the following diagram
Ambient Temp Hood Angle
and instructions should be referred to.
[ °F ]
-10
-5
0
5
10
15
20
25
30
35
40
45
The transformer is 208/230 – 24volt AC. For proper
Transformer
The low ambient kit is designed to function with both
connections to the outdoor unit, the following diagram
The transformer is 208/230 – 24 volt AC. For proper connections to
208/230 volt and also 460 volt outdoor units.
the outdoor unit, refer to the following diagram and instructions.
and instructions should be referred to.
On 208 volt units the CNAC2 connector will provide
208 volts to the control transformer.
On 230 volt units the CNAC2 connector will provide
230 volts to the control transformer.
The 460 volt units include a transformer that reduces
the outdoor unit internal voltage to 230 volts. Because
of this, on the 460 volt units the CNAC2 connector will
also provide 230 volts to the control transformer.
Once the proper connection is confirmed, measure
voltage on the primary side of the transformer. It
should be 208 or 230 +- 10% depending on the supply
voltage at the outdoor unit. If there is no voltage on the
primary side of the transformer check the fuse that is
located in the fuse holder inside the outdoor unit. See
The low ambient kit is designed to function with both
wiring diagram for fuse location. Once power has been
208/230 volt and also 460 volt outdoor units.
The low ambient kit is designed to function with both 208/230 volt
confirmed at the primary side of the transformer, check
On 208 volt units the CNAC2 connector will provide and also 460 volt outdoor units.
the secondary/low voltage side of the transformer it
On 208 volt units the CNAC2 connector will provide 208 volts to the
208 volts to the control transformer.
should be approximately 27 volts. If no voltage is
control transformer.
On 230 volt units the CNAC2 connector will provide
present, replace transformer.
On 230 volt units the CNAC2 connector will provide 230 volts to the
230 volts to the control transformer.
control transformer.
The 460 volt units include a transformer that reduces
The 460 volt units include a transformer that reduces the outdoor
Interlock Relay
the outdoor unit internal voltage to 230 volts. Because
unit internal voltage to 230 volts. Because of this, on the 460 volt
The interlock relay uses a normally closed contact to
of this, on the 460 volt units the CNAC2 connector will units the CNAC2 connector will also provide 230 volts to the control
allow power to flow to the transformer energizing the
transformer.
also provide 230 volts to the control transformer.
low ambient kit control circuitry. Any time the outdoor
Once the proper connection is confirmed, measure voltage on the
Once the proper connection is confirmed, measure
unit is in cooling mode, this contact will be in closed.
primary side of the transformer. It should be 208 or 230 +- 10%
voltage on the primary side of the transformer. It
When the outdoor unit reversing valves energizes
depending on the supply voltage at the outdoor unit. If there is no
should be 208 or 230 +- 10% depending on the supply
voltage on the primary side of the transformer, check the fuse that
(switches to heating mode) the coil of the relay is
voltage at the outdoor unit. If there is no voltage on the
is located in the fuse holder inside the outdoor unit. See the wiring
energized, opening this contact. This in-turn de-
primary side of the transformer check the fuse that is diagram for fuse location. Once power has been confirmed at the
energizes the transformer, disconnecting power to the
primary side of the transformer, check the secondary/low voltage
located in the fuse holder inside the outdoor unit. See
low ambient kit control circuitry. This allows the damper
side of the transformer. It should be approximately 27 volts. If no
wiring diagram for fuse location. Once power has been
to spring return to the full open position during heating
voltage is present, replace the transformer.
confirmed at the primary side of the transformer, check
mode.
the secondary/low voltage side of the transformer it
To check, make sure the contact is closed when the
Specifications are subject to change without notice.
should be approximately 27 volts. If no voltage is
outdoor unit is in cooling mode (coil de-energized) and
present, replace transformer.
the contact is open when the outdoor unit is in the
4
heating mode (coil energized).
Output Voltage
[ ° ] v
80 8.78
80 8.78
70 7.9
70 7.9
70 7.9
70 7.9
60 7.04
60 7.04
60 7.04
60 7.04
OPEN 2
OPEN 2
Interlock relay
The interlock relay uses a normally closed contact to allow power to
flow to the transformer energizing the low ambient kit control circuitry.
Any time the outdoor unit is in cooling mode, this contact will be in
closed. When the outdoor unit reversing valves energizes (switches to
heating mode) the coil of the relay is energized, opening this contact.
This in turn de-energizes the transformer, disconnecting power to
the low ambient kit control circuitry. This allows the damper to spring
return to the full open position during heating mode.
To check, make sure the contact is closed when the outdoor unit is in
cooling mode (coil de-energized) and the contact is open when the
outdoor unit is in the heating mode (coil energized).
Damper Actuator
Damper actuator
Before trouble shooting the damper motor, verify the two factory
Before trouble shooting the damper motor, verify the
switches are in the position shown below.
Resistance
two factory switches are in the position shown below.
Ω
117960
100184
85340
72906
62460
53658
46220
39917
34562
30000
26104
22767
Damper Actuator
Before trouble shooting the damper motor, verify the
Make sure the motor has 24 volts on the (1) Common and (2) +Hot
Make sure the motor has 24 volts on the (1) Common
two factory switches are in the position shown below.
connections. If not, find the cause of the voltage failure and correct.
and (2) +Hot connections. If not, find the cause of the
The damper actuator receives a DC voltage signal from the circuit
voltage failure and correct.
board. This voltage can be measured between (1) Common and (3)
The damper actuator receives a DC voltage signal
2-10VDC connections.
from the circuit board. This voltage can be measured
The damper actuator has an angle indicator where it clamps onto the
damper shaft linkage.
between (1) Common and (3) 2-10VDC connections.
Compare the DC voltage supply to the damper angle indicator position
The damper actuator has an angle indicator where it
in the chart below. The angle should be within 2% of the chart shown
clamps onto the damper shaft linkage.
below. If not, check to make sure the damper started off in the correct
Compare the DC voltage supply to the damper angle
position, 0 Degrees.
indicator position in the chart below. The angle should
be within 2% of the chart shown below. If not, check to
IMPORTANT!
It's possible that during shipping, the damper shaft may have
make sure the damper started off in the correct
moved in the actuator shaft clamp assembly. See Section 3.
position. 0 Degrees
Damper Blade Adjustment.
IMPORTANT!
If the damper actuator angle doesn't match within 2%, with the
It's possible that during shipping, the damper shaft
corresponding control board voltage supplied as shown below, the
Make sure the motor has 24 volts on the (1) Common
may have moved in the actuator shaft clamp
damper actuator should be replaced.
and (2) +Hot connections. If not, find the cause of the
assembly. With power off, make sure the damper is
voltage failure and correct.
in the full open position. 0 degrees If necessary, Ambient Temp
The damper actuator receives a DC voltage signal
[ °F ]
loosen the shaft clamp on the actuator, move the
from the circuit board. This voltage can be measured
-10
damper to the 100% open position, and re-clamp
between (1) Common and (3) 2-10VDC connections.
-5
tightly.
The damper actuator has an angle indicator where it
0
clamps onto the damper shaft linkage.
5
If the damper actuator angle doesn't match within 2%,
Compare the DC voltage supply to the damper angle
10
with the corresponding control board voltage supplied
indicator position in the chart below. The angle should
15
as shown below, the damper actuator should be
be within 2% of the chart shown below. If not, check to
20
replaced.
make sure the damper started off in the correct
25
position. 0 Degrees 30
Outdoor
35
Temperature
40
IMPORTANT!
Above 52
45
It's possible that during shipping, the damper shaft
52
may have moved in the actuator shaft clamp
50
assembly. With power off, make sure the damper is
45
in the full open position. 0 degrees If necessary,
40
35
loosen the shaft clamp on the actuator, move the
30
damper to the 100% open position, and re-clamp
25
Damper Actuator
black
Black
(1)
red
Red
(2)
white
White
(3)
Orange (5)
Y=0 Y=0
Factory switch positions
Damper Actuator
black
Black
red
Red
white
White
Orange
Y=0 Y=0
Factory switch positions
Hood Angle Output Voltage
[ ° ]
80
80
70
70
70
70
60
60
60
Thermistor Control board
60
Ohms DC volts output
OPEN
o
N/A
F
OPEN
18,873
19,903
22,767
26,104
30,000
34,562
39,917
Common
+ Hot
2-10VDC
(1) Common
(2) + Hot
(3) 2-10VDC
(5)
Resistance
v Ω
8.78 117960
8.78 100184
7.9 85340
7.9 72906
7.9 62460
7.9 53658
7.04 46220
7.04 39917
7.04 34562
Damper
7.04 30000
Angle
2 26104
o
2.00
0 full open
2 22767
o
2.00
0
3.25 o
15
4.50 o
30
© 2019 Mitsubishi Electric US, Inc.
o
5.80
45
o
7.04
60
o
7.90
70
o
8.75
80