Hitachi RAS-24MH1 User manual

NO. 0559E
SPECIFICATIONS AND PARTS ARE SUBJECT TO CHANGE FOR IMPROVEMENT
ROOM AIR CONDITIONER
INDOOR UNIT + OUTDOOR UNIT
JANUARY 2014 Refrigeration & Air-Conditioning Division
SERVICE MANUAL
PM
REFER TO THE FOUNDATION MANUAL
TECHNICAL INFORMATION
FOR SERVICE PERSONNEL ONLY
SPECIFICATIONS
RAS-24MH1
CONTENTS
SPECIFICATIONS------------------------------------------------------ 4
HOW TO USE ---------------------------------------------------------- 6
CONSTRUCTION AND DIMENSIONAL DIAGRAM---------28
MAIN PARTS COMPONENT --------------------------------------30
WIRING DIAGRAM ---------------------------------------------------32
CIRCUIT DIAGRAM --------------------------------------------------33
PRINTED WIRING BOARD LOCATION DIAGRAM --------39
BLOCK DIAGRAM ----------------------------------------------------42
BASIC MODE ----------------------------------------------------------43
REFRIGERATING CYCLE DIAGRAM---------------------------57
AUTO SWING FUNCTION -----------------------------------------58
DESCRIPTION OF MAIN CIRCUIT OPERATION-----------59
SERVICE CALL Q & A----------------------------------------------72
TROUBLE SHOOTING ----------------------------------------------76
PARTS LIST AND DIAGRAM--------------------------------------96
RAS-24MH1/RAC-24MH1
After installation
RAC-24MH1
(W)
(A)
(kW)
(B.T.U./h)
(W)
(A)
(kW)
(B.T.U./h)
W
H
D
(kg)
(WALL TYPE)
TYPE
MODEL
POWER SOURCE
TOTAL INPUT
TOTAL AMPERES
CAPACITY
TOTAL INPUT
TOTAL AMPERES
CAPACITY
DIMENSIONS
(mm)
NET WEIGHT
COOLING
HEATING
OUTDOOR UNIT
RAC-24MH1
INDOOR UNIT
RAS-24MH1
1030
295
207
12
1 PHASE, 50 Hz, 220-230V
1,850 (155 – 2,300)
8.50 ~ 8.10
6.00 (0.9 – 6.5)
20,480 (3,072 – 22,190)
1,880 (115 – 2,550)
8.60 ~ 8.25
6.80 (0.9 ~ 8.50)
23,210 (3,072 – 29,000)
850
650
298
45

– i –
SAFETY DURING REPAIR WORK
1. In order to disassemble and repair
the unit in question, be sure to
disconnect the power cord plug
from the power outlet before starting
the work.
2. If it is necessary to replace any parts, they should be replaced with respective genuine parts for the unit,
and the replacement must be effected in correct manner according to the instructions in the Service Manual
of the unit.
If the contacts of electrical
parts are defective, replace the
electrical parts without trying to
repair them.
3. After completion of repairs, the initial state
should be restored.
4. Lead wires should be connected and laid as
in the initial state.
5. Modification of the unit by user himself should
absolutely be prohibited.
6. Tools and measuring instruments for use in repairs or inspection should be accurately calibrated in advance.
7. In installing the unit having been repaired, be careful to prevent the occurence of any accident such as
electrical shock, leak of current, or bodily injury due to the drop of any part.
8. To check the insulation of the unit, measure the insulation resistance between the power cord plug and
grounding terminal of the unit. The insulation resistance should be 1M or more as measured by a 500V
DC megger.
9. The initial location of installation such as window, floor or the other should be checked for being and safe
enough to support the repaired unit again.
If it is found not so strong and safe, the unit should be installed at the initial location reinforced or at a new
location.
10. Any inflammable thing should never
be placed about the location of
installation.
11. Check the grounding to see whether
it is proper or not, and if it is found
improper, connect the grounding
terminal to the earth.

– 1 –
WORKING STANDARDS FOR PREVENTING BREAKAGE OF SEMICONDUCTORS
1. Scope
The standards provide for items to be generally observed in carrying and handling semiconductors in relative
manufacturers during maintenance and handling thereof. (They apply the same to handling of abnormal
goods such as rejected goods being returned).
2. Object parts
(1) Micro computer
(2) Integrated circuits (IC)
(3) Field-effect transistors (FET)
(4) P.C. boards or the like on which the parts mentioned in (1) and (2) of this paragraph are equipped.
3. Items to be observed in handling
(1) Use a conductive container for carrying and storing of parts. (Even rejected goods should be handled
in the same way).
Fig. 1. Conductive Container
(2) When any part is handled uncovered (in counting, packing and the like), the handling person must always
use himself as a body earth. (Make yourself a body earth by passing 1M (earth resistance through a
ring or bracelet).
(3) Be careful not to touch the parts with your clothing when you hold a part even if a body earth is being
taken.
(4) Be sure to place a part on a metal plate with grounding.
(5) Be careful not to fail to turn off power when you repair the printed circuit board. At the same time, try
to repair the printed circuit board on a grounded metal plate.
1M
Fig. 2. Body Earth
Body earth
(Elimik conductive band)
Clip for connection with a
grounding wire
IC
A conductive polyvinyl bag IC
Conductive sponge

– 2 –
(6) Use a three wire type soldering iron including a grounding wire.
Bare copper wire (for body earth)
Working table
Resistor of 1 M (1/2W)
Earth wire
Fig. 3. Grounding of the working table
Screw stop at the screwed
part using a rag plate
Soldering iron
Grounding
wire
Fig. 4. Grounding a soldering iron
Use a high insulation mode (100V, 10M or higher) when ordinary iron is to be used.
(7) In checking circuits for maintenance, inspection or some others, be careful not to have the test probes of
the measuring instrument shortcircuit a load circuit or the like.
Metal plate (of aluminium, stainless steel, etc.)
Staple

– 3 –
1. In quiet or stop operation, slight flowing noise of refrigerant in the refrigerating cycle is heard occasionally,
but this noise is not abnormal for the operation.
2. When it thunders near by, it is recommend to stop the operation and to disconnect the power cord plug
from the power outlet for safety.
3. In the event of power failure, the air conditioner will restart automatically in the previously selected mode
once the power is restored. In the event of power failure during TIMER operation, the air conditioner will
not start automatically. Re-press ON/OFF button after 3 minutes from when the unit off or power recovery.
4. If the room air conditioner is stopped by adjusting thermostat, or missoperation, and re-start in a moment,
there is occasion that the cooling and heating operation does not start for 3 minutes, it is not abnormal
and this is the result of the operation of IC delay circuit. This IC delay circuit ensures that there is no
danger of blowing fuse or damaging parts even if operation is restarted accidentally.
5. This room air conditioner should not be used at the cooling operation when the outside temperature is
below –10°C (14°F).
6. This room air conditioner (the reverse cycle) should not be used when the outside temperature is below
–15°C (5°F).
If the reverse cycle is used under this condition, the outside heat exchanger is frosted and efficiency falls.
7. When the outside heat exchanger is frosted, the frost is melted by operating the hot gas system, it is not
trouble that at this time fan stops and the vapour may rise from the outside heat exchanger.
CAUTION