
11 Maintenance notes
General notes
SMGB0091 rev.2 - 11/2015
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11
11.1.3
Insufficient cooling performance when a long piping is applied
Question and answer for the field work:
Example 2: Insufficient cooling performance when a long piping is applied
Phenomenon
Sufficient cooling was not available for an indoor unit that was located at the farthest position.
Cause
If the location of a RASC unit is 20 meters lower than the location of the indoor units, resetting of the DIP
switch DSW2 is required.
However, no setting was performed. Therefore, the largest discharge pressure was not increased.
This resulted in an insufficient cooling performance for the indoor unit.
Insufficient
cooling
Indoor units
RASC unit
Countermeasure
The setting of the DSW2 was changed.
Remarks
Pay special attention to the size of liquid pipe. Refer to
“3.3 Refrigerant piping range”
11.1.4 Abnormally high operation sound (in-the-ceiling type indoor unit)
Question and answer for the field work
Example 3: Abnormally high operation sound (in-the-ceiling type indoor unit)
Phenomenon
The operation sound at the "HIGH" speed was abnormally high.
Cause
The indoor units were installed without the ducts. Since there scarcely was any external static pressure, an
abnormally big air volume was supplied. This resulted in a higher air speed through the heat exchanger
Damper
Indoor unit
Filter
Countermeasure
In order to reduce the airflow rate, a plate that is used as a damper at the discharge gas side was added.
Remarks
Note that the running current is increased when no external pressure is given to the indoor unit.
This results in an overheating.