Emerson 2 - Manual (Page 9)

Introduction
3
1.3.1 Refrigeration System Options
Low Pressure Switch and Low Pressure Bypass Timer
Low Pressure Switch: Used to protect the InteleCool2 if the evaporator blower fails, the air filter
becomes clogged, the refrigeration circuit malfunctions or if there is loss of refrigerant. The low pres-
sure switch is activated when the suction pressure drops below its cutout setting. When activated, the
low pressure switch inhibits operation of the compressor and condenser fan. The switch will automat-
ically reset once the system pressure rises above its cut-in setting.
Low Pressure Bypass Timer: Also known as the Condenser Low Ambient Control or Winter Start
Option), the low pressure switch is used when starting the system when the outdoor temperature is
low. A few minutes after start-up, the low pressure switch resumes normal operation. This option can
be used for applications down to 50°F (10°C). For control down to -20°F (-28.9°C), use the T-pack1 or
T-pack2.
T-pack1
This option provides a Low Pressure Switch, a Low Pressure Bypass Timer (described above), and a
Fan Cycle Control. This option package is one of the preferred control packages for telecommunica-
tion industry applications.
The Fan Cycle Control, also known as the Condenser Fan Cycling Control, consists of a reverse-acting
pressure switch. When the outdoor temperature is low, the pressure switch cycles the condenser fan
to maintain discharge pressures that will allow the systems to function. It is to be used when the out-
door ambient temperature is lower than 50°F (10°C) down to -20°F (-28.9°C).
T-pack2
This option includes a Low Pressure Switch, a Low Pressure Bypass Timer (described above), and an
adjustable Fan Cycle Control, which acts as described in the preceding paragraph, except that it is
adjustable. This option package is one of the preferred control packages for telecommunication indus-
try applications.
1.4 Ancillary Components
Wall-Mounted Thermostat
The thermostat provides for heating/cooling application with separate fan control. Supplied with a
thermostat sub-base.
Indoor Supply/Return Grilles
The supply grille is an aluminum louvered, double deflection type grille allowing user adjustment of
direction of air distribution. The return grille is an aluminum louvered, fixed, single-deflection style
grille.
Additional Spare Filters
Additional sets of the 20% efficiency rated filters (efficiency based on ASHRAE standard 52-1) may be
selected.
1.5 Accessories
Dual Unit Control
The hinged cover dual unit control (DUC) has a two-stage heat/cool thermostat with individual heat-
ing and cooling setpoints, adjustable interstage differentials, and bimetallic elements. The control
features a solid state timer with 1-2-4-8 day sequence. Unit lead selector, unit 1 & 2 power-on LEDs,
unit 1 or 2 lead unit LEDs, 48 hour program save on loss of power, industry standard connections and
24V power from each unit. The DUC provides auto sequencing and displays on-status and operating-
status parameters.
Tele2 Control
This microprocessor-based controller controls two InteleCool2 units. The unit has a 10-key keypad,
four-row by 20-column LCD, an RS-232 modem port, and an RS-232 terminal port. It allows up to
eight customer-selectable, isolated normally open, dry contact alarm inputs. The Tele2 control
requires either a THS28-30 or a THS28-60 sensor assembly. Models are available for
120/50-60/1 VAC, 230/50-60/1 VAC or 48 VDC power.