Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 912

FDC-HKX
(2) Reference Effect of noise
¡ When noises inturude into remote controller.
Abnormal or irregular display such as the flashing of irrelevant display (lamp) (for example, LEDs of cooling and heating illumi-
nated simultaneously or the like) is observed even if the remote controller is not operated or the remote or the remote controller
and, as the result, the operation of units may be disabled or similar abnormal phenomenons are observed.
¡ When noises intruded into the microcomputer of printed circuit board; State of operation becomes abnormal such as the units
perform irregular operation while the remote controller is not operated, the operation cannot be stopped with the remote controller,
etc.
Electro magnetic noise prevention (example)
• Cover the entire surface of control box or the
inside of unit cover with the cover foil or cover
the entire unit with a wire net.
Remote controller wire
Use the shield or
twist pair wires
Remote controller
Put in a steel case
Separate from cutting machine as far
as possible. This is very effective
because the effect of noise is inverse
proportion to 1.5 times of distance.
Beware of noises
transmitted via air.
(b) Error diagnosis procedures at the indoor unit side
To diagnose the error, measure the voltage (AC,DC), resistance, etc. at each connector around the printed circuit board of indoor
unit PCB on the inspection display or the operation state of unit (no operation of comressor or blower, no switching of 4-way valve,
etc.). If any defective parts are discovered, replace with the assembly of parts as shown below.
(i) Unit of replacement parts releated to indoor unit printed circuit board ( Electric components on and around the
microcomputer)
Indoor unit printed circuit board, thermistor (Return air, heat exchanger), remote controller switch, limit switch, transformer,
fuse
Note (1) Judges the troubles on the parts of driving power circuit or cooling cycle with the ordinary check method.
910
Interisified shielding
of control section
l
2
Shut off electrically
the noise source or put
it in a shield room.
Signal wire
Outdoor
(indoor unit)
unit
l
1
Power
cable Unless it has a sufficient current capacity,
mini split current drops momentarily at the
Distribution
start/stop of cutting machine.
board
A void supply from the same distribution
board to prevent troubles by the power
source propagation. Install the line filter at
the power supply of cuting machine of mini
split (Positive grounding is necessary.)
• Insert in a steel pipe shield.
Make a positive
ground