Mitsubishi Electric HP120TNU-A Service Handbook page 229

[7-8 Error Code Definitions and Solutions: Codes [6000 - 6999] ]
7-8-25 Error Code [6846]
1. Error code definition
Start-up time over
2. Error definition and error detection method
Start-up time over The unit cannot finish start-up process within 4 minutes after power on.
3. Cause, check method and remedy
(1) Contact failure of indoor/outdoor unit connecting wire
(2) Diameter or length of indoor/outdoor unit connecting wire is out
of specified capacity.
(3) 2 or more outdoor units have refrigerant address "0". (In case of
group control)
(4) Noise has entered into power supply or indoor/outdoor unit con-
necting wire.
Note: Refer also to the Service Handbook for the indoor units.
66
- chapter 7
Cause Check method and remedy
Check disconnection or looseness or polarity
of indoor/outdoor unit connecting wire of in-
door and outdoor units.
Check the following: Diameter of the cables
used for indoor-outdoor lines; maximum line
distance between indoor and outdoor units
(max. 50 m); maximum line distance be-
tween indoor units (daisy-changed cables)
(max. 30 m); and if flat cables such as VVF is
used, make sure they are connected in the
order of S1, S2, and S3.
When units are controlled as groups, check
the refrigerant address (SW1 (3-6) on the
outdoor unit control board settings) for dupli-
cates.
Check the transmission lines for problems.
HWE18220_GB