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5. Once flame is established the integrated gas unit controller
(IGC) will look for 24- -v power to W1 and W2. If there is
24- -v power to W1 only, the IGC will switch the induced- -
draft motor down to low speed and maintain low stage on
the gas valve. If there is 24- -v power to both W1 and W2,
the IGC will maintain the induced- -draft motor on high
speed and switch the gas valve to high stage.
6. With the desired temperature set several degrees higher than
the room temperature, most thermostats will energize low
and high stage. Verify that the gas valve is energized on
high stage and the induced- -draft motor is on high speed.
7. Verify proper operation of low stage (induced- -draft motor
on low speed and gas valve on high stage) by turning the
heating temperature control setting down until the desired
temperature is 1 degree above room temperature. Most ther-
mostats will energize low stage only with a 1 degree differ-
ential.
8. The evaporator fan will turn on 30 sec after the flame has
been established. If there is 24- -v power to W1 only, the fan
will run on low heat speed. If there is 24- -v power to W1
and W2, the fan will run on high heat speed. Once the heat-
ing coll is satisfied, the IGC will turn the fan off after a
field- -selectable fan delay of 90, 120, 150, or 180 sec is
completed.
For 460 VAC Models:
1. Place room thermostat SYSTEM switch in the HEAT
position and the fan switch is placed in AUTO position.
2. Set the heating temperature control of the thermostat above
room temperature.
3. The induced- -draft motor will start.
4. On a call for heating, the main burner should light within 5
sec of the spark being energized. If the burners do not light,
there is a 22- -sec delay before another 5- -sec try. If the
burners still do not light, this sequence is repeated. If the
burners do not light within 15 minutes from the initial call
for heat, there is a lockout. To reset the control, break the
24- -v power to W.
5. The evaporator fan will turn on 45 sec after the flame has
been established. The evaporator fan will turn off 45 sec
after the thermostat has been satisfied. Please note that the
integrated gas unit controller (IGC) has the capability to
automatically reduce the evaporator "ON" delay and in-
crease the evaporator "OFF" delay in the event of high duct
static and/or partially- -clogged filter.
Check Gas Input
Check gas input and manifold pressure after unit start- -up (See
Table 6 or 7). If adjustment is required proceed as follows:
S The rated gas inputs shown in Table 6 or 7 are for altitudes from
sea level to 2000 ft (610 m) above sea level. These inputs are
based on natural gas with a heating value of 1025 Btu/ft
specific gravity, or propane gas with a heating value of 2500
3
Btu/ft
at 1.5 specific gravity.
IN THE U.S.A.:
The input rating for altitudes above 2,000 ft (610 m) must be
reduced by 4% for each 1,000 ft (305 m) above see level.
For installations below 2,000 ft (610 m), refer to the unit rating
plate.
For installations above 2,000 ft (610 m). multiply the input on the
rating plate by the derate multiplier in Table 3 for correct input rate.
If the natural gas is not derated by the gas utility company, refer to
Table 4 (208/230 VAC models) or Table 5 (460 VAC models) for
correct orifice sizes and manifold pressures.
Table 3 – Altitude Derate Multiplier for U.S.A.*
ALTITUDE FT (M)
0--- 2000
(0--- 610)
2001--- 3000*
(610--- 914)
3001--- 4000
(915--- 1219)
4001--- 5000
(1220--- 1524)
5001--- 6000
(1524 --- 1829)
6001--- 7000
(1829--- 2134)
7001--- 8000
(2134--- 2438)
8001--- 9000
(2439--- 2743)
9001--- 10,000
(2744--- 3048)
*In Canada see Canadian Altitude Adjustment.
{Derate multiplier factors are based on midpoint altitude for altitude range.
IN CANADA:
The input rating for altitudes from 2,000 (610 m) to 4,500 ft (1372
m) above sea level must be derated 10% by an authorized Gas
Conversion Station or Dealer.
EXAMPLE:
90,000 Btu/hr Input Furnace Installed at 4300 ft.
Furnace Input Rate at
Sea Level
90,000
When the gas supply being used has a different heating value or
specific gravity, refer to national and local codes, or contact your
distributor to determine the required orifice size.
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in reduced unit
and/or component life.
Do Not redrill an orifice. Improper drilling (burrs,
out- -of- -round holes, etc.) can cause excessive burner noise
and misdirection of burner flame. If orifice hole appears
damaged or it is suspected to have been redrilled, check
orifice hole with a numbered drill bit of correct size.
Adjust Gas Input
The gas input to the unit is determined by measuring the gas flow
at the meter or by measuring the manifold pressure. Measuring the
gas flow at the meter is recommended for natural gas units. The
manifold pressure must be measured to determine the input of
propane gas units.
3
at 0.60
Measure Gas Flow (Natural Gas Units)
Minor adjustment to the gas flow can be made by changing the
manifold pressure(s). The manifold pressure(s) must be maintained
between 3.2 and 3.8 IN. W.C. for high stage and between 1.4 and
2.0 IN. W.C. for low stage (208/230 VAC models). For 460 VAC
models, manifold pressure must be maintained between 3.2 and 3.8
IN. W.C.
17
DERATE MULTIPLIER
PERCENT OF DERATE
FACTOR{
0
1.00
8--- 12
0.90
12--- 16
0.86
16--- 20
0.82
20--- 24
0.78
24--- 28
0.74
28--- 32
0.70
32--- 36
0.66
36--- 40
0.62
X Derate Multiplier
= Furnace Input Rate at
Factor
Installation Altitude
X
0.90
=
CAUTION
81,000
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