Air Conditioning The Computer Room; Main Features Of The Floor-Duct Air Conditioners; Features Of Air-Conditioner For Computer Room - Mitsubishi Electric PFD-P250VM-E Service Manual

8. Air Conditioning the Computer Room

8-1 Main Features of the Floor-Duct Air Conditioners

This system is installed by building a floor over an existing floor and
using the space between these two floors as an air-conditioning duct.
This system has the following characteristics:
1 The temperature and humidity can efficiently and reliably be controlled, since the air-conditioned air is
sent directly to the machine.
2 It provides a comfortable environment for the operator, since the air can be conditioned to best suit the
needs of the operator and machines.
3 It is favorable in terms of appearance because the air-conditioning duct is out of sight.
4 The location of the duct is irrelevant when considering adding new machines or rearranging the existing
machines, since the entire floor serves as the air duct.
Free-access top floor
Caution
(1) Unlike plenum ventilation and overhead-duct type conditioners, since the conditioned air is not mixed
with the air in the room, the air that comes out of the unit has to meet the predetermined conditions
(constant temperature/constant humidity) at the time the air exits the unit.
Close attention must be paid to the auto-controlling system.
(2) Dust in the duct space (between the free-access top floor and the existing floor) must be thoroughly
removed before installing the unit.
(3) Since the existing floor is cooled by the unit, it may produce dews on the ceiling of the room down
below.

8-2 Features of air-conditioner for computer room

Air-conditioner for computer room is designed to maintain a constant room temperature and humidity. For
underfloor air supply systems, providing air that meets predetermined requirements is a must. The com-
pressor installed in this unit runs year around. The capacity controlled compressor regulates the outlet air
temperature (or inlet air temperature) depending on the load change. The humidifier (Configure to Order)
installed in this unit humidifies a room to a target humidity, and regulates the humidity. With priority dehu-
midification control (a dehumidifier must be installed on site), a room is dehumidified to a target humidity.
Since the reheat function is not equipped, the room temperature may drop below the predetermined tem-
perature due to a load inside the room. Therefore, the absolute humidity drops whereas the relative
humidity may not drop to a target humidity.
Ceiling
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