Mitsubishi Electric MXZ-SM72TAM-U1 Service Manual page 72

6607 (A7): No ACK error
Abnormal points and detection methods
■ Common to all
An abnormality detected by the sending side controller
when receiving no ACK from the receiving side, though
signal was once sent. The sending side detects the abnor-
mality when that occurs 6 times in succession at 30 sec-
ond intervals.
■ The address/attribute of the outdoor unit was displayed:
An abnormality detected by the indoor unit if it received no
ACK when transmitting signal to the outdoor unit.
■ The address/attribute of the indoor unit was displayed:
An abnormality detected by the remote controller if it re-
ceived no ACK when transmitting signal to the indoor unit.
■ The address/attribute of the remote controller was displayed:
An abnormality detected by the indoor unit if it received no
ACK when transmitting signal to the remote controller.
OCH800A_72
Causes and checkpoints
• The previous address unit does not exist since the ad-
dress switch was changed while power was on.
• Decline of transmission voltage/signal because the
transmission line exceeds the following limits.
- Indoor/outdoor transmission line maximum distance:
656 ft (200 m)
- For remote controller line: 39 ft (12 m)
• Decline of transmission voltage/signal due to un-
matched transmission line types
- Types for shield line: CVVS, CPEVS, or MVVS
- Line diameter: AWG 16 (1.25 mm
• Decline of transmission voltage/signal due to excessive
number of connected units
• Malfunction due to accidental disturbance such as noise
or lightning surge
• Defect of error source controller
• Contact failure of indoor/outdoor unit transmission line.
• Disconnection of transmission connector (CN2M) on
indoor unit.
• Malfunction of sending/receiving circuit on indoor/out-
door unit.
• Disconnection of the connectors on the circuit board
• Cut off of power supply for outdoor unit caused by high
pressure protection (63H).
• While operating with the indoor units in a different refrig-
erant system, an abnormality is detected when the in-
door unit transmits signal to the remote controller during
the other refrigerant-system outdoor unit is turned OFF,
or within 2 minutes after it turned back ON.
• Contact failure of indoor unit or remote controller trans-
mission line
• Disconnection of transmission connector (CN2M) on
indoor unit
• Malfunction of sending/receiving circuit on indoor unit or
remote controller
• While operating with the indoor units in a different refrig-
erant system, an abnormality is detected when the in-
door unit transmits signal to the remote controller during
the other refrigerant-system outdoor unit is turned OFF,
or within 2 minutes after it turned back ON.
• Contact failure of indoor unit or remote controller trans-
mission line
• Disconnection of transmission connector (CN2M) on
indoor unit
• Malfunction of sending/receiving circuit on indoor unit or
remote controller
Chart 1 of 4
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