SC360 System Controller
18-HD95D1-1C-EN 9
Thermostat
(UX360)
System Controller
(SC360)
Distribution Board
Air Handler
Outdoor Unit
7. CAN Low Voltage Troubleshooting
• 24 VAC is required to power up the SC360 and UX360
• 24 VAC is required at the outdoor unit for Smart Charge
automatic charging
• 24 VAC is required at the outdoor unit if Load Shed is desired
TROUBLESHOOTING STEPS
DESCRIPTION
Bus Idle
Expected Measurement
2 - 4 VDC between DH and GND
2 - 4 VDC between DL and GND
Voltage measured from DH to DL will vary depending on bus
traffic
Resistance Between DH and DL
1
Appropriate range can vary depending on the communicating equipment installed on the system
Expected Measurement
60 +/- 10 ohms can be expected when the SC360,
communicating indoor unit and communicating variable speed
outdoor unit are installed.
90 +/- 10 ohms can be expected with no communicating outdoor
unit installed
Lower than appropriate range
Possible short on the bus between DH and DL
Higher than appropriate range
Possible open circuit on the bus
Resistance Between DH and GND
2
Expected Measurement
1 Mohms or greater
1
All power to the system must be turned OFF.
2
Device must be powered OFF and disconnected from the CAN bus.
