Unit installation

July 2009 Application Note 1014
©2012 Mitsubishi Electric US, Inc.
P a g e | 2
Mitsubishi Electric/HVAC Division offers air conditioning equipment specifically for
thermal comfort conditioning. While the units are designed for cooling and in the case of
Heat Pumps for heating and not for humidity control there is a function to reduce the
latent content in the air. Dry Mode is the operating mode for Mr. Slim and CITY MULTI
indoor units used to reduce the moisture content of the air in the conditioned space
served by the indoor unit – without significantly reducing the room temperature.
The reduction is accomplished by reducing the airflow across the indoor coil and
controlling the temperature of the coil surface so that the surface remains slightly below
the dew point of the return air. The coil temperature is maintained by a combination of
time based compressor or LEV – Linear Expansion Valve – operation, temperature
output information from the smart coil and room temperature sensor input.
Dry Mode is available on all of the Mitsubishi/HVAC indoor units and is selectable on Mr.
Slim M or P Series via the unit’s Remote Controller (Wired or Wireless) or in the case of
CITY MULTI by the local controller, central controller (G-50A/GB-50) or the TG-2000
software.
Dry Mode is selected by pressing the MODE button until the display reads “Dry”. Then
from the SET TEMP buttons the desired space temperature is selected to control room
comfort. To use Dry Mode the room temperature must be greater than 65°F.
In Dry Mode, the indoor fan runs on very LOW speed during compressor operation (Mr.
Slim 1:1 Systems) or when the LEV is open (Mr. Slim Multi Zone or CITY MULTI
Systems.) The fan speed cannot be changed using the remote controller while in Dry
Mode. Operation is a combination of time based cooling related to setpoint and space
temperature. An example of the operating sequence is shown in Table 1.
Table 1. An example of the operating sequence
CITY MULTI
Indoor LEV
THERMOSTAT
ROOM TEMP
ON
OFF
CALLING
82° or more
9 Minutes
3 Minutes
CALLING
79° - 82°
7 Minutes
3 Minutes
CALLING
75° - 79°
5 Minutes
3 Minutes
CALLING
64° - 75°
3 Minutes
3 Minutes
CALLING
less than 64°
--
Always
SATISFIED
64° or more
3 Minutes
10
Minutes
less than 64°
--
Always
Dry mode establishes the refrigerant flow such that the coil temperature is low enough to
condense the water vapor in the air but minimize reduction of the air temperature. This is
a cumulative action so the air becomes dryer with each pass of the air through the coil.
Due to continuing improvement, above specification may be subject to change without notice.
2013 P-Series and M-Series - Application Notes (June 2013)
APP-32