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Low Ambient Cooling Operation Down to 40°F (4°C)
In low ambient RTU conditions when the temperature is be-
tween 55°F (13°C) and 40°F (4°C), the low ambient switch
(LAS) will be active and the outdoor-fans will run to the pre-
set factory outdoor-fan speed. When the temperature is greater
than 65°F (18°C), the low ambient switch will deactivate and
the outdoor-fans will run in the standard cooling mode. If the
Outdoor Fan Select Switch (see Fig. 46) is in the up position,
the outdoor fans will run in the fan cycle speed mode (FCS) set
to 250 rpm. If the outdoor fan select switch is in the down posi-
tion, the outdoor fans will run in the minimum fan speed mode
(MIN) set to 160 rpm regardless of the cooling demand.
The 50LC size 14-26 units have a SPST normally open low
ambient switch wired across the TS and OF terminal and a
jumper placed across the PS terminal (see Fig. 47). When the
LAS is active, the switch will close, making contact to the OF
terminal. This is done for units that require all outdoor fans to
run at the same pre-set factory Low Ambient Speed.
Table 6 shows the operation of the outdoor fan for each unit.
Fig. 46 — Outdoor Fan Speed Select Switch
Fig. 47 — Schematic of SPST Low Ambient Switch
Heating
In the Heating Mode (W1 on the thermostat), power is applied
to the G and W1 terminal at the ISC board and energizes the
first state of electric heat. Upon more call for heat (W2 at the
thermostat), power is applied to the G and W2 terminal at the
ISC board and energizes the second state of electric heat. The
VFD-controlled indoor fan will operate at high speed regard-
less of the heating demand.
EconoMi$er
®
X (Factory Option)
The EconoMi$er X system is an expandable economizer con-
trol system, which includes a W7220 economizer module (con-
troller) with an LCD and keypad (see Fig. 48). The W7220 can
be configured with optional sensors.
Fig. 48 — W7220 Economizer Module
The W7220 economizer module can be used as a stand-alone
economizer module wired directly to a commercial set-back
space thermostat and sensors to provide outside air dry-bulb
economizer control.
The W7220 economizer module can be connected to optional
sensors for single or differential enthalpy control. The W7220
economizer module provides power and communications for
the sensors.
The W7220 economizer module automatically detects sensors
by polling to determine which sensors are present. If a sensor
loses communications after it has been detected, the W7220
economizer controller indicates a device fail error on its LCD.
SYSTEM COMPONENTS
The EconoMi$er X system includes an economizer module,
20k mixed air sensor, damper actuator, and either a 20k out-
door air temperature sensor or S-Bus enthalpy sensors.
Economizer Module
The module is the core of the EconoMi$er X system. The mod-
ule is mounted in the unit’s control box, and includes the user
interface for the system. The W7220 economizer module pro-
vides the basic inputs and outputs to provide simple economiz-
er control. When used with the optional sensors, the economiz-
er module provides more advanced economizer functionality.
S-Bus Enthalpy Control Sensors
The sensor is a combination temperature and humidity sensor
which is powered by and communicates on the S-Bus. Up to
three sensors may be configured with the W7220 economizer
module.
CO
2
Sensor (optional)
The CO
2
sensor can be added for Demand Controlled Ventila-
tion (DCV).
SPECIFICATIONS
W7220 Economizer Module
The module is designed for use with 2 to 10 vdc or bus com-
municating actuator. The module includes terminals for CO
2
sensor, mixed air sensor, and an outdoor dry bulb sensor. En-
thalpy and other options are available with bus sensors.
Table 6 — Low Ambient Temperature Outdoor Fan
Control
50LC
SIZE
NO. OF
FANS ON
NO. OF
FANS
OFF
SWITCH
OUTDOOR
FAN
SELECT
SWITCH
RPM
14
3 0
SPST
Up
250
17
4 0
SPST
Up
250
20
4 0
SPST
Up
250
24
6 0
SPST
Up
250
26
6 0
SPST
Up
250
OF SPEED
SELECT
ON
FCS
MIN
OFF
JUMPER ON
LAS
SPST
PS
PS
TS
OF
Summary of Contents for 50LC 14
Page 26: ...26 Fig 34 50LC 14 26 Control Wiring Diagram...
Page 27: ...27 Fig 35 50LC 14 26 RTU Open Control Wiring Diagram...
Page 28: ...28 Fig 36 50LC 14 20 208 230V 3 Phase Power Wiring Diagram...
Page 29: ...29 Fig 37 50LC 24 26 208 230V 3 Phase Power Wiring Diagram...
Page 30: ...30 Fig 38 50LC 14 26 460V 575V 3 Phase Power Wiring Diagram...