Hitachi RAS-(4-12)HNP(1)(E) - Insufficient Cooling Performance When a Long Piping Is Applied; Abnormally High Operation Sound (in the Ceiling Type Indoor Unit)

12 Maintenance notes
473
SMGB0087 rev.0 - 12/2013
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 DSW2 is required.
However no setting was performed. Therefore the largest discharge pressure was not increased. This resulted
in an insufcient cooling performance for the indoor unit.
Insufcient
cooling
Indoor units
Outdoor
unit
Countermeasure The setting of the DSW2 was changed.
Remarks
Pay special attention to the size of liquid pipe. Refer to “3. 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 was any external static pressure a big air volu-
me was supplied. This resulted in a higher air speed through the heat exchanger.
Damper
Indoor unit
Air lter
Countermeasure In order to reduce the airow set the indoor unit at “Low static pressure” setting.