44
Table 30B — Altitude Compensation* —
Low NOx Units
*As the height above sea level increases, there is less oxygen per
cubic foot of air. Therefore, the input rate should be reduced at
higher altitudes.
†Orifices are available through your local Carrier distributor.
Heating
1. Purge gas supply line of air by opening union ahead of
gas valve. If gas odor is detected, tighten union and wait
5 minutes before proceeding.
2. Turn on electrical supply and manual gas valve.
3. Set system switch selector at HEAT position and fan
switch at AUTO. or ON position. Set heating temperature
lever above room temperature.
4. The induced-draft motor will start.
5. After a call for heating, the main burners should light
within 5 seconds. If the burner does not light, then there is
a 22-second delay before another 5-second try. If the
burner still does not light, the time delay is repeated. If the
burner does not light within 15 minutes, there is a lock-
out. To reset the control, break the 24-v power to W1.
6. The evaporator-fan motor will turn on 45 seconds after
the burners are ignited.
7. The evaporator-fan motor will turn off 45 seconds after
thermostat temperature is satisfied.
8. Adjust airflow to obtain a temperature rise within the
range specified on the unit nameplate.
NOTE: The default value for the evaporator-fan motor ON/
OFF delay is 45 seconds. The Integrated Gas Unit Controller
(IGC) modifies this value when abnormal limit switch cycles
occur. Based upon unit operating conditions, the ON delay can
be reduced to 0 seconds and the OFF delay can be extended to
180 seconds. When one flash of the LED is observed, the
evaporator-fan ON/OFF delay has been modified.
If the limit switch trips at the start of the heating cycle dur-
ing the evaporator ON delay, the time period of the ON delay
for the next cycle will be 5 seconds less than the time at which
the switch tripped. (Example: If the limit switch trips at 30 sec-
onds, the evaporator-fan ON delay for the next cycle will occur
at 25 seconds.) To prevent short-cycling, a 5-second reduction
will only occur if a minimum of 10 minutes has elapsed since
the last call for heating.
The evaporator-fan OFF delay can also be modified. Once
the call for heating has ended, there is a 10-minute period dur-
ing which the modification can occur. If the limit switch trips
during this period, the evaporator-fan OFF delay will increase
by 15 seconds. A maximum of 9 trips can occur, extending the
evaporator-fan OFF delay to 180 seconds.
To restore the original default value, reset the power to the
unit.
TO SHUT OFF UNIT — Set system selector switch at OFF
position. Resetting heating selector lever below room tempera-
ture will temporarily shut unit off until space temperature falls
below thermostat setting.
Safety Relief —
A soft solder joint at the suction service
Schrader port provides pressure relief under abnormal tempera-
ture and pressure conditions (i.e., fire in building).
Ventilation (Continuous Fan) —
Set fan and system
selector switches at ON and OFF positions, respectively. Evap-
orator fan operates continuously to provide constant air circula-
tion. When the evaporator-fan selector switch is turned to
the OFF position, there is a 30-second delay before the fan
turns off.
Operating Sequence
COOLING, UNITS WITHOUT ECONOMI$ER2 — When
thermostat calls for cooling, terminals G and Y1 are energized,
and the indoor (evaporator) fan motor (IFM), compressor, and
outdoor (condenser) fan motor (OFM) start. The OFM runs con-
tinuously while the unit is in cooling. When the thermostat is sat-
isfied, compressor contactor (C) is deenergized and the com-
pressor and OFM shut off. After a 30-second delay, the IFM
shuts off. If the thermostat fan selector switch is in the ON posi-
tion, the evaporator motor will run continuously.
HEATING, UNITS WITHOUT ECONOMI$ER2 — When
the thermostat calls for heating, terminal W1 is energized. To
prevent thermostat short-cycling, the unit is locked into the
Heating mode for at least 1 minute when W1 is energized. The
induced-draft motor is energized and the burner ignition
sequence begins. The indoor (evaporator) fan motor (IFM) is
energized 45 seconds after a flame is ignited. On units
equipped for two stages of heat, when additional heat is
needed, W2 is energized and the high-fire solenoid on the main
gas valve (MGV) is energized. When the thermostat is satisfied
and W1 is deenergized, the IFM stops after a 45-second time-
off delay.
COOLING, UNITS WITH ECONOMI$ER2 — When free
cooling is not available, the compressors will be controlled by
the zone thermostat. When free cooling is available,
the outdoor-air damper is positioned through the use of a
Proportional-Integral (PI) control process to provide a 55 F
supply-air temperature into the zone. As the supply-air temper-
ature fluctuates above or below 55 F, the dampers will be mod-
ulated (open or close) to bring the supply-air temperature back
within control.
If mechanical cooling is utilized with free cooling, the
outdoor-air damper will be locked into its current position at
the time the compressor is started. If the increase in cooling ca-
pacity causes the supply-air temperature to drop below 45 F,
then the outdoor air damper position will be decreased to the
minimum position. If the supply-air temperature continues to
fall, the outdoor-air damper will close. See Fig. 41 for
EconoMi$er2 outdoor-air damper operation.
If optional power exhaust is installed, as the outdoor air
damper opens and closes, the power exhaust fans will be ener-
gized and deenergized.
If field-installed accessory CO
2
sensors are connected to the
EconoMi$er2 control, a PI-controlled demand ventilation strat-
egy will begin to operate. As the CO
2
level in the zone increas-
es above the CO
2
set point, the minimum position of the damp-
er will be increased proportionally. As the CO
2
level decreases
because of the increase in fresh air, the outdoor-air damper will
be proportionally closed.
ELEVATION
(ft)
60,000 AND
90,000 BTUH
NOMINAL INPUT
120,000 BTUH
NOMINAL INPUT
Natural
Gas
Orifice
Size†
Liquid
Propane
Orifice
Size†
Natural
Gas
Orifice
Size
Liquid
Propane
Orifice
Size†
0-2,000
38
45
32
42
2,000
40
47
33
43
3,000
41
48
35
43
4,000
42
49
36
44
5,000
43
49
37
45
6,000
43
50
38
45
7,000
44
50
39
46
8,000
45
51
41
47
9,000
46
52
42
48
10,000
47
52
43
49
11,000
48
53
44
50
12,000
49
53
44
51
13,000
50
54
46
52
14,000
51
54
47
52
Summary of Contents for 48TF004-007
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