Haier 2U18MS2VHB Service Manual page 72

Ductless multi-split heat pump, outdoor/indoor, wall mount - highwall, 2'x2' compact cassette, 3'x3' large cassette, slim duct, mid-static ducted, medium static ducted, console
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The Indoor Unit Circuit Board communicates with the outdoor unit ECU
via a connection at Terminal Block screw 3. The data pulse that sends the
communication information can be measured with a voltmeter placed to DCV
range. From the ground connection at the Terminal Block to the Number 3
screw connection, the voltage should pulse up and down when data is being
Line voltage to power the indoor unit comes in on Terminal Block connections 1
and 2. Power connects from these terminal connections to CH- 1 and CH-2 on
the circuit board. If the board does not respond to commands and has no display,
check for line voltage at these connections. When power is present at the indoor
board, the wired controller will be energized.
The connections on the indoor board are shown here in the schematic drawing.
This control board has control over the fan louver movement, manual fan blower control, indoor coil temperature and indoor air
temperature sensing functions. All operational decisions are controlled by the OUTDOOR UNIT ECU.
The control board has a replaceable 5A 250V fuse that protects against excessive current. If power is present at the board but the
board does not work, check for continuity through the fuse. Replace if the fuse is open.
The indoor unit temperature sensors are connected at Plug CN-13. When testing the calibration of these sensors, the wires can
be released from the plug by pressing on the tension tab on the side of the plug.
There 3 motors that control the directional movement of the accessory louver. The motor connects to the circuit board at Plug
CN-14, CN-15 and CN-16. The motors are located in the louver assembly.
The blower motor is connected to the circuit board at plug CN-6.
SW1 DIP Switches
There are two sets of DIP switches on the Circuit Board. SW3 is for factory
use only. SW1 is used to set the configuration of the indoor unit operation.
The first three switches SW1-1, SW1-2 and SW1-3 select the indoor unit
Air Delivery Power is set with DIP Switches SW1-4 and SW1-5. The settings
are shown in Hydrostatic Selection of 0Pa, up to 30Pa. SW1-7 and SW1-8
define the unit type. The conversions are as follows:
10Pa= .04"w.c.
• Recommended settings are for motorized Louver set to 10Pa.
• Ducting limited to a total of .12"w.c. External Static set to 30Pa.
Indoor uni t
3wire 1 4AWG
Control Wiring
Indoor uni t
3wire 1 4AWG
Control Wiring
Outdoor unit
Outdoor unit

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