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Fig. 56 —
Outdoor Fan Speed Select Switch
Fig. 57 —
Schematic of SPDT Low Ambient Switch
Table 9 shows the operation of the outdoor fan for size 08, 09 and
12 units.
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 con
-
trolled through a room thermostat set for fan auto, the indoor 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 ig
-
nite within 5 seconds. If the burners do not light, there is a 22-sec
-
ond delay before another 5-second attempt. This sequence is re
-
peated for 15 minutes or until the burners light. If, after the 15
minutes, the burners still have not lit, heating is locked out. To re
-
set the control, break 24 vac power to the thermostat.
When gas ignition occurs, the IGC board will continue to monitor
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 45 seconds
then stop. If the over temperature limit opens after the indoor mo
-
tor is stopped, but within 10 minutes of W1 becoming inactive, on
the next cycle the time will be extended by 15 seconds. The maxi
-
mum 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 power to
the second stage of the main gas valve. When the thermostat is sat
-
isfied, the gas valve closes, interrupting the flow of gas to the main
burners.
EconoMi$er
®
X (Factory Option)
The EconoMi$er X system is an expandable economizer control
system, which includes a W7220 economizer module (controller)
with an LCD and keypad (see Fig. 58). The W7220 can be config
-
ured with optional sensors.
Fig. 58 —
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$er X system includes an economizer module, 20k
mixed air sensor, damper actuator, and either a 20k outdoor air
temperature sensor or S-Bus enthalpy sensors.
Economizer Module
The module is the core of the EconoMi$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.
CO
2
Sensor (optional)
The CO
2
sensor can be added for Demand Controlled Ventilation
(DCV).
Table 9 —
Low Ambient Temperature Outdoor Fan
Control
48LC
SIZE
NO. OF
FANS ON
NO. OF
FANS OFF SWITCH
OUTDOOR FAN
SELECT
SWITCH
RPM
08
2
1
(1) SPDT
Down
160
09
2
1
(1) SPDT
Down
160
12
2
1
(1) SPDT
Down
160
OF SPEED
SELECT
ON
FCS
MIN
OFF
LAS
SPDT
PS
PS
OF
REMOVE JUMPER
ODF RELAY
24VAC
TB-4
Summary of Contents for 48LC Series
Page 5: ...5 Fig 2 Unit Dimensional Drawing Size 08 Unit ...
Page 6: ...6 Fig 2 Unit Dimensional Drawing Size 08 Unit cont ...
Page 7: ...7 Fig 3 Unit Dimensional Drawing Size 09 and 12 Units ...
Page 8: ...8 Fig 3 Unit Dimensional Drawing Size 09 and 12 Units cont ...
Page 11: ...11 Fig 6 Roof Curb Details Size 08 12 Units ...
Page 21: ...21 Fig 34 48LC 08 12 Electro mechanical Control Wiring Diagram ...
Page 22: ...22 Fig 35 48LC 08 12 RTU Open Control Wiring Diagram ...
Page 23: ...23 Fig 36 48LC 08 12 SystemVu Control Wiring Diagram ...
Page 25: ...25 Fig 38 48LC 08 12 Typical Power Wiring Diagram SystemVu Control 208 230 v Unit Shown ...
Page 61: ......