Hitachi RAS-4-HNCE - Insufficient Cooling Performance When a Long Piping Is Applied

12. Maintenance notes
457
SMGB0079 rev.0 - 01/2013
12
12.1.3 Insufcient cooling performance when a long piping is applied
Question and answer for the eld work
Example 2: Insufcient cooling performance when a long piping is applied
Phenomenon Sufcient cooling was not available for an indoor unit that was located at the farthest position.
Cause
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-
sufcient cooling performance for the indoor unit.
Outdoor unit
Indoor units
Insucient cooling
Countermeasure The setting of the DSW2 was changed.
Remarks Pay special attention to the size of liquid pipe. Refer to Piping work and refrigerant charge chapter for details.
12.1.4 Abnormally high operation sound (in the ceiling type indoor unit).
Question and answer for the eld 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
A. Filter
Countermeasure In order to reduce the airow 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 over-
heating.