Mitsubishi Electric PUZ-HA24NHA1 Service Manual page 40

Abnormal point and detection method
Check Code
NO ACK signal
1. Transmitting side controller detects
abnormal if a message was transmitted
but there is no reply (ACK) that a mes-
sage was received. Transmitting side
detects abnormality every 30 seconds, 6
times continuously.
Note: The address and attribute displayed
at remote controller is indicate the
controller that did not reply (ACK).
2. If displayed address or attribute is out-
door unit, indoor unit detects abnormality
when indoor unit transmitted to outdoor
unit and there was no reply (ACK).
A7
(6607)
3. If displayed address or attribute is indoor
unit, remote controller detects abnormal-
ity when remote controller transmitted to
indoor unit and there was no reply (ACK).
OCH750A
Cause
Common factor that has no rela-
tion with abnormality source.
1 The unit of former address
does not exist as address
switch has changed while the
unit was energized.
2 Voltage drop and weak signal
which lead communication
error are caused by over-range
transmission wire.
• Maximum distance··· 656 ft [200 m]
• Remote controller line (39 ft [12m])
3 Voltage drop and weak signal
which lead communication
error are 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 [AWG16]
2
or more
4 Voltage drop and weak signal
which lead communication
error are caused by over-
numbered units.
5 Accidental malfunction of
abnormality-detected controller
(noise, thunder surge)
6 Defective of abnormality-
detected controller
1 Contact failure of transmission
wire of outdoor unit or indoor unit
2 Disconnection of transmission
connector (CN2M) of outdoor
unit
3 Defective transmitting receiving
circuit of outdoor unit or indoor
unit
1 During group operation with
indoor unit of multi- refrigerant
system, if remote controller
transmit to indoor unit while
outdoor unit power supply
of one refrigerant system is
turned off or within 2 min-
utes of restart, abnormality is
detected.
2 Contact failure of transmission
wire of remote controller or
indoor unit
3 Disconnection of transmission
connector (CN2M) of indoor unit
4 Defective transmitting receiving
circuit of indoor unit or remote
controller
40
Judgment and action
Always try the following when the error
"A7" occurs.
1 Turn off the power supply of outdoor unit
and indoor unit and FRESH MASTER or
LOSSNAY at the same time for 2 minutes or
more, and turn the power on again. If mal-
function was accidental, the unit returns to
normal.
2 Check address switch of abnormality-detect-
ed address.
3 Check disconnection or looseness of abnor-
mality-detected transmission wire (terminal
block and connector)
4 Check if tolerance range of transmission wire
is not exceeded.
5 Check if type of transmission wire is correct
or not.
If there were some troubles of 1–5 above,
repair the defective, then turn off the power
supply of outdoor unit and indoor unit and
FRESH MASTER or LOSSNAY at the same
time for 2 minutes or more, and turn the power
on again.
• If there was no trouble with 1–5 above in
single refrigerant system (one outdoor unit),
controller of displayed address or attribute is
defective.
• If there was no trouble with 1–5 above in dif-
ferent refrigerant system (2 or more outdoor
units), judge with 6.
6 If address of abnormality source is the
address that should not exist, there is the
unit that memorizes nonexistent address
information. Delete unused address informa-
tion 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 differ-
ent refrigerant system.
If there was no trouble with 1–6 above,
replace the controller board of displayed
address or attribute.
If the unit does not return to normal, multi-con-
troller board of outdoor unit may be defective
(repeater circuit).
Replace multi-controller board one by one to
check if the unit returns to normal.
Continued to the next page.