Mitsubishi Electric CITY MULTI PUMY-P112VKM6 Service Manual page 69

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.
■ The address/attribute of Fresh Master was displayed:
An abnormality detected by the indoor unit if it received no
ACK when transmitting signal to the Fresh Master.
OCH790 _69
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:
200 m [656 ft]
- For remote controller line: 12 m [39 ft]
• Decline of transmission voltage/signal due to un-
matched transmission line types
- Types for shield line: CVVS, CPEVS, or MVVS
- Line diameter: 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
• While the indoor unit is operating with the remote con-
troller in a different refrigerant system, an abnormality is
detected when the indoor unit transmits signal to the
remote controller while the outdoor unit in the same
refrigerant system as the Fresh Master is turned OFF,
or within 2 minutes after it turned back ON.
• Contact failure of indoor unit or Fresh Master transmis-
sion line
• Disconnection of transmission connector (CN2M) on
indoor unit or Fresh Master
• Malfunction of sending/receiving circuit on indoor unit or
Fresh Master
Chart 1 of 4
2 [AWG 16] or more