System Components - Carrier WeatherExpert 48LC 07 Series Installation Instructions Manual

OF SPEED
Fig. 48 — Outdoor Fan Speed Select Switch
JUMPER ON
PS
TS
Fig. 49 — Schematic of SPST Low Ambient Switch
Table 8 shows the operation of the outdoor fan for size 07
units.
Table 8 — Low Ambient Temperature Outdoor Fan
Controls
48LC NO. OF NO. OF
SIZE FANS ON FANS OFF
2 0
07
Heating
In the Heating Mode (W1 and G on the thermostat), the ISC
board sends power to W on the IGC board. Assuming the unit
is controlled through a room thermostat set for fan auto, the in-
door-fan motor will energize and the outdoor-air dampers will
open to their minimum position. The ISC board upon seeing
W1 and G ON will turn the indoor fan to high speed.
The IGC board starts its gas ignition process. A check is made
to ensure that the rollout switch and limit switch are closed. If
the check was successful, the induced draft motor is energized,
and when its speed is satisfactory, as proven by the flue gas
pressure switch, the ignition activation period begins. The
burners will ignite within 5 seconds. If the burners do not light,
there is a 22-second delay before another 5-second attempt.
This sequence is repeated for 15 minutes or until the burners
light. If, after the 15 minutes, the burners still have not lit, heat-
ing is locked out. To reset the control, break 24 vac power to
the thermostat.
When gas ignition occurs, the IGC board will continue to mon-
itor the condition of the rollout switch, the limit switches, the
flue gas pressure switch, as well as the flame sensor.
When W1 is turned OFF, the IGC board turns off the gas valve.
The IGC board has a delay time before it turns IFO=OFF. At
this time, the ISC board sees W1=OFF and IFO=ON. The ISC
will keep the indoor fan ON high speed. Once the IGC board
delay times out, the ISC board will see W1=OFF and
IFO=OFF, which then turns the indoor fan OFF.
If the call for W1 lasted less than 1 minute, the heating cycle
will not terminate until 1 minute after W1 became active. If the
unit is controlled through a room thermostat set for fan auto,
the indoor fan motor will continue to operate for an additional
SELECT
ON
FCS
MIN
OFF
PS
OF
LAS
SPST
OUTDOOR
FAN
SWITCH
SELECT
SWITCH
SPST Up
45 seconds, then stop. If the over temperature limit opens after
the indoor motor is stopped, but within 10 minutes of W1 be-
coming inactive, on the next cycle the time will be extended by
15 seconds. The maximum delay is 3 minutes. Once modified,
the fan OFF delay will not change back to 45 seconds unless
power is reset to the control. A LED indicator is provided on
the IGC to monitor operation.
When additional heat is required, W2 closes and initiates pow-
er to the second stage of the main gas valve. When the thermo-
stat is satisfied, the gas valve closes, interrupting the flow of
gas to the main burners.
EconoMi$er ®
The EconoMi$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. 50). The W7220 can
be configured with optional sensors.
RPM
Fig. 50 — W7220 Economizer Module
The W7220 economizer module can be used as a stand-alone
250
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
module is mounted in the unit's control box, and includes the
user interface for the system. The W7220 economizer module
provides the basic inputs and outputs to provide simple
economizer control. When used with the optional sensors, the
economizer 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.
31
X (Factory Option)