Mitsubishi Electric PU(H)Y-P250YGM-A Service Handbook page 154

(3) Check method and remedy
1) Measures against noise
Check the followings when noise exists on the wave or the errors described in (1) occur.
Check 1. The transmission line and the power
that the 220~240 V line are not wired too
wiring closely.
work is
2. The transmission line is not bundled
per-
with that for another systems.
formed
accord-
ing to wir-
3. The specified wire is used for the
ing
transmission line.
specifica-
tions.
4. When the transmission line is daisy-
chained on the indoor unit terminals,
are the shields daisy-chained on the
terminals, too?
Check 5. Is the grounding of the shield of the
that the transmission line (for indoor unit con-
ground- trol) provided on the indoor unit?
ing work
6. Check the treatment method of the
is per-
shield of the transmission line (for cen-
formed
tralized control).
accord-
ing to
ground-
ing speci-
fications.
2) Check the followings when the error "6607" occurs, or "HO" appears on the display on the remote controller.
Error code definition
7. The farthest distance of transmission line is 200m
or longer.
8. The types of transmission lines are different.
9. Check the state of the choke coil on the transmis-
sion power supply circuit.
10.Indoor unit or remote controller failure
Error code definition
- 145 -
Remedy
Isolate the transmission line from the power line (5cm or
more). Do not insert them in the same Do not insert them in
the same conduit.
The transmission line must be isolated from another transmis-
sion line.
When they are bundled, erroneous operation may be caused.
Use the specified transmission line.
Type: Shielded wire CVVS/CPEVS/MVVS (For M-NET re-
mote controller)
2
Diameter: 1.25mm or more
(Remote controller wire: 0.5 - 1.25mm
The transmission is two-wire daisy-chained. The shielded
wire must be also daisy-chained.
When the shielded cable is not daisy-chained, the noise can-
not be reduced enough.
One point grounding must be provided on the outdoor unit.
If no grounding is provided, the noise on the transmission line
cannot escape leading to change of the transmission signal.
When group operation of indoor units connected to different
outdoor units is performed, provide grounding of the shield of
the transmission line for centralized control at the point of out-
door unit, and when the system controller is used, provide
grounding at the point of the system controller, so that the ef-
fect of noise can be minimized.
The environment against noise varies depending on the dis-
tance of the transmission lines, the number of the connected
units, the type of the controllers to be connected, or the envi-
ronment of the installation site. Therefore, the transmission
line work for centralized control must be performed as follows.
(1) When no grounding is provided
Group operation of indoor units connected to different
outdoor units: One point grounding on one outdoor unit
(power supply unit)
Use of MELANS: Grounding on the main controller
(power supply device)
(2) When an error occurs even though one point grounding
is provided: Ground the shield on all outdoor units.
Remedy
Check that the farthest distance from the outdoor unit to the
indoor unit and to the remote controller is within 200m.
Use the specified transmission line.
Type: Shielded wire CVVS/CPEVS/MVVS (For M-NET re-
mote controller)
2
Diameter: 1.25mm or more
(Remote controller wire: 0.5 - 1.25mm
When resistance of the choke coil (L2) is between 0.5 and 2.6
ohm, the choke coil is normal.
When resistance (R3) on the outdoor unit MAIN board is
1kohm 5%, it is normal. Connectors CNS1 and CNS2 must
be removed when resistance is measured.
Replace the indoor unit controller board or the remote control-
ler.
[ IX Troubleshooting ]
2
)
2
)