Mitsubishi Electric PUHY-M200YNW-A1 Service Handbook page 34

[1-5 Precautions for Wiring ]
2) Check the wires are securely fastened to the screw terminals.
Screw the screws straight down so as not to damage the screw threads.
Hold the two round terminals back to back to ensure that the screw will screw down straight.
After tightening the screw, mark a line through the screw head, washer, and terminals with a permanent marker.
Example
Mark a line.
Poor contact caused by loose screws may result in overheating and fire.
Continued use of the damaged circuit board may cause overheating and fire.
BS_01_G
Daisy-chain
Power wires, transmission lines, centralized transmission lines
Place the round terminals back to back.
Power supply terminal block, indoor-outdoor transmission line terminal block,
and centralized controller transmission line
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