Mitsubishi Electric PUZ-SM100VKA2 Service Manual page 39

Check code Abnormal points and detection method
NO ACK signal
1. Transmitting side controller detects
abnormal if a message was transmitted
but there is no reply (ACK) that a
message was received. Transmitting
side detects abnormality every 30
seconds, 6 times continuously.
Note:
The address and attribute displayed at
remote controller indicate the controller
that did not reply (ACK).
2. If displayed address or attribute is
outdoor unit, indoor unit detects
abnormality when indoor unit transmits
signal to outdoor unit and there was no
reply (ACK).
A7
(6607)
3. If displayed address or attribute is
indoor unit, remote controller detects
abnormality when remote controller
transmits signal to indoor unit and there
was no reply (ACK).
OCH774A
Cause
Common factor that has no
relation with abnormality source
The unit of former address
does not exist as address
switch has changed while the
unit was energized.
Extinction of transmission wire
voltage and signal is caused
by over-range transmission
wire.
• Maximum distance ....... 200m
• Remote controller line .. (12m)
Extinction of transmission wire
voltage and signal is caused by
type-unmatched transmission
wire.
Type ......
With shield wire-
CVVS, CPEVS
With normal wire (no shield)-
VCTF, VCTFK, CVV
CVS, VVR, VVF, VCT
Diameter ..... 1.25mm
or more
2
Extinction of transmission wire
voltage and signal is caused
by over-numbered units.
Accidental malfunction of
abnormality-detected controller
(noise, thunder surge)
Defective of abnormality-
generated controller
Contact failure of transmission
wire of outdoor unit or indoor
unit
Disconnection of transmission
connector (CN2M) of outdoor
unit
Defective transmitting receiving
circuit of outdoor unit or indoor
unit
During group operation with
indoor unit of multi- refrigerant
system, if remote controller
transmits signal to indoor
unit while outdoor unit power
supply of one refrigerant
system is turned off or within 2
minutes of restart, abnormality
is detected.
Contact failure of transmission
wire of remote controller or
indoor unit
Disconnection of transmission
connector (CN2M) of indoor
unit
Defective transmitting receiving
circuit of indoor unit or remote
controller
39
Judgment and action
Always try the following when the error
"A7" occurs.
Turn off the power supply of outdoor
unit, indoor unit and FRESH MASTER or
LOSSNAY at the same time for 2 minutes
or more, and turn the power on again. If
malfunction was accidental, the unit returns
to normal.
Check address switch of abnormality-
generated address.
Check disconnection or looseness of
abnormality-generated or abnormality-
detected transmission wire (terminal block
and connector)
Check if tolerance range of transmission
wire is not exceeded.
Check if type of transmission wire is correct
or not.
If the cause of trouble is not any of
above, repair the defect, then turn off the
power supply of outdoor unit, indoor unit and
FRESH MASTER or LOSSNAY at the same
time for 2 minutes or more, and turn the power
on again.
• If the cause of trouble is not any of
above in single refrigerant system (one
outdoor unit), controller of displayed address
or attribute is defective.
• If the cause of trouble is not any of
above in different refrigerant system (2 or
more outdoor units), judge with
If address of abnormality source is the
address that should not exist, there is the
unit that memorizes nonexistent address
information. Delete useless address
information with manual setting function of
remote controller.
Only the system FRESH MASTER or
LOSSNAY are connected to, or the system
that is equipped with group setting of
different refrigerant system.
If the cause of trouble is not any of
– above, replace the controller board of
displayed address or attribute.
If the unit does not return normally, multi-
controller board of outdoor unit may be
defective (repeater circuit).
Replace multi-controller board one by one to
check if the unit returns normally.
Continued to the next page.
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