Insufficient Cooling Performance When A Long Piping Is Applied - Hitachi RAS-2-HVNP Service Manual

12. Maintenance notes
12.1.3 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.
If the location of an outdoor unit is 20 meters lower than the location of the indoor units resetting of the DIP switch DSW3
is required.
However no setting was performed. Therefore the largest discharge pressure was not increased. This resulted in an in-
sufficient cooling performance for the indoor unit.
Cause
Countermeasure The setting of the DSW2 was changed.
Remarks Pay special attention to the size of liquid pipe. Refer to
12.1.4 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.
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.
Cause
Countermeasure In order to reduce the airflow rate a plate that is used as a damper at the discharge gas side was added.
Note that the running current is increased when no external pressure is given to the indoor unit. This results in an over-
Remarks
heating.
457
SMGB0079 rev.0 - 01/2013
Indoor units
Insu cient cooling
Piping work and refrigerant charge
Damper
Indoor unit
Outdoor unit
chapter for details.
A. Filter
12