Installation Manual

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MULTI Air Conditioner
Publication No: PWE09050
Publication Date: June 2009
Technical Information
Title: Handling the return air temperature sensor (TH1) according to the return duct structure
1. Symptom
When a bend in the return duct is very close to the unit connected to the duct, actual return air
temperature is different from the return air temperature detected by the sensor on the unit (TH1).
2. Reason
Since a bend in the return duct causes an uneven airflow distribution, the temperature difference
occurs between actual return air temperature and the return air temperature detected by the sensor
when the return air temperature is measured at a single point.
When the unit has a straight return duct or no return duct, there is no temperature difference between
actual return air temperature and the return air temperature detected by the sensor.
3. Remedy
If there is a problem with room temperature control, apply the following remedies.
1) When using a remote controller with a temperature sensor, AND installing the controller in a
location where an average room temperature can be detected,
Use the sensor on the remote controller to control the room temperature.
2) Other than section 1) above
Use a Remote Sensor (sold separately) (PAC-SE41TS-E). (Refer to the attached document.)
1. Install this sensor inside the room.
2. Install this sensor in a location where an actual return air temperature can be detected inside
the duct.
4. Additional notes
When using a standard unit that takes in outside air through a return duct, apply the remedies shown
in section 3.
<Reference>
Mitsubishi Electric Co.
AC & R System Works
THA
THA
THA
TH1
THX
TH1
TH1
High airflow velocity
Outside air intake
Detected
temperature
(reference for
section 3)
A
ctual return air temperature < TH1
(THA)
A
ctual return air temperature > TH1
(THA)
A
ctual return air temperature < TH1=THX
(THA)