Abnormally High Operation Sound (In The Ceiling Type Indoor Unit) - Hitachi RAS-5HVRNM1E Service Manual

12 Maintenace notes

12.4 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.
Remarks Note that the running current is increased when no external pressure is given to the indoor unit. This results in an overheating.
461
SMGB0060 rev. 1- 12/2010
Damper
Indoor unit
A. Filter
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