Service Manual

GSM-204-323
Thermal management system (TMS)
31st Oct 01
Tech. 3–4
Technical Description: Horizon macro outdoor
CONTROLLED INTRODUCTION
68P02902W02-A
Heat exchanger
components
The heat exchanger consists of the following items:
Recuperators
The recuperators are manufactured from a series of epoxy resin coated
aluminium sheets, sealed at alternate edges to form two sets of narrow air
passages, one set for the ambient air and one set for the recirculated air, but the
air streams do not mix.
Ambient air fans (external fans)
The two ambient air fans are located one on each side of the unit. The fans are
of the radial type with backward curved blades for maximum efficiency. The fan
impeller is direct driven by a –48 V dc motor with a solid state commutator. The
fan contains its own pulse width modulation (PWM) speed control circuitry.
Recirculation air fans (internal fans)
The recirculation air fans are located at the rear of the unit. The fans are of the
same type and operate the same way as the ambient air fans.
AC heater elements
The ac heater elements are located in the recirculation air inlet to the cabinet
enclosures, at the top of the unit. There are two individual heaters, each with its
own high limit thermostat attached.
TMS control board
The control board is located in the top right side of the TMS unit behind the
cable well. The control board has the following functions:
 Interpretation of thermal data from the TMS temperature sensors.
 Control of the speed of ambient and recirculation fans.
 Control of the operation of ac heater elements.
 Generation of TMS alarm signals.
 Configuration of heater elements for 230 V ac or 110 V ac input voltages.
Temperature sensors
The temperature sensors are located at the top of the TMS unit in the
recirculation air return aperture. The functions of the TMS temperature sensors
are described in Horizon
macro outdoor temperature control in this chapter.