Service manual

Operation Section
20
6.2 Basic Operation of The Office Pro 36 Electrical Circuit
• There are two basic components used to control the operation of the Office Pro 36 electrical
system:
- Control panel assembly
- Control box
• The control panel assembly contains the control panel, control board (with inputs for the freeze
and room temperature thermistors), drain switch, high pressure switch and a microprocessor.
(1) Fan mode
High Fan Mode
• When the FAN MODE button on the control panel is pressed, the microprocessor turns on “FAN
HI” “COOL OFF” indication of LCD and activates both the fan on relay and fan mode relay. This
sends line voltage (208/230 VAC) from the fan on relay to the N.O. (normally open) contacts of
the fan mode relay. This output is connected to the J8 terminal (relay board) where the high
speed wire of the fan motor is connected.
• When this button is pressed again, fan turns to low mode (see below). Press again, fan stops.
Low Fan Mode
• When the FAN MODE button on the control panel is pressed again, the microprocessor turns on
“FAN LO” “COOL OFF” indication of LCD and activates both the fan on relay and fan mode relay.
This sends line voltage (208/230 VAC) from the fan on relay to the N.C. (normally closed)
contacts of the fan mode relay. This output is connected to the J7 terminal (relay board) where
the low speed wire of the fan motor is connected.
• When this button is pressed again, fan stops.
(2) Cool mode
• In addition to fan mode (as described above), when the COOL ON/OFF button on the control
panel is pressed, the microprocessor turns on “COOL ON” indication of LCD and if the
temperature set point is less than the current room temperature, activates the compressor relay
(relay board) after 120 sec delay. This sends line voltage (208/230 VAC) to the J4 terminal (relay
board) where compressor wire is connected. Then compressor turns on for Cooling Operation.
• Condenser fan mode is automatically switched
depending on room temperature. When room
temperature is approximately. 79 °F (26 °C) or
greater, fan mode is switched LO to HIGH.
When room temperature is approximately.
75 °F (24 °C), fan mode is switched HI to LO.
I001770
75 °F
(24 °C)
Room Temperature
(LO)
(High)
Condenser Fan
79 °F
(26 °C)