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5. Gas Supply and Piping
!
CARBON MONOXIDE POISONING, FIRE AND EX-
PLOSION HAZARD.
Failure to follow these instructions can result in
death, personal injury and/or property damage.
Models designated for Natural Gas are to be used
with Natural Gas ONLY, unless properly converted to
use with LP gas.
NOTE: The rating plate is stamped with the model number, gas
type and gas input rating. In addition, models manufactured for
sale in Canada have orifice size information stamped on the rating
plate.
Alternate BTUH Input Ratings (USA Only)
The input rating of these furnaces can be changed from the stan-
dard input rating to the alternate input rating shown in Table 5, by
changing the main burner orifices. NOTE: The input rating ot
80,000 BTUH models cannot be changed from the standard input.
Changing of burner orifices MUST be done by a qualified service
technician. See section on changing orifices or following page.
Table 5
Alternate Input Ratings, USA ONLY.
BTUH
BTUH
Standard
Alternate
Rating
Rating
50,000
40,000
75,000
60,000
100,000
80,000
125,000
100,000
Supply Pressure
!
FIRE HAZARD
Failure to properly set input pressure can result in death,
personal injury and/or property damage.
Do NOT set input rating above that shown on rating plate.
1.
Supply pressure can be checked using the
the supply side of the gas valve.
2.
Gas input to burners MUST NOT exceed the rated input
shown on rating plate.
3.
Do NOT allow minimum gas supply pressure to vary down-
ward. Doing so will decrease input to furnace. Refer to
Table 6 for normal gas supply and manifold pressures.
26
Natural
LP
Gas
Gas
Orifice
Orifice
#44
#55
#44
#55
#44
#55
#44
#55
1
/
² NPT port on
8
Table 6
Gas Pressures Below 2000¢ ¢ ¢ ¢
Gas
Supply Pressure
T
Type
Recommended
Natural
7²
LP
11²
Important Note:
· With Propane gas, the rated input is obtained when the
BTU content is 2,500 BTU per cubic foot and manifold
pressure set at 10² ² ² ² W.C.
· If Propane gas has a different BTU content, orifices
MUST be changed by licensed Propane installer.
· Measured input can NOT exceed rated input.
· Any major change in gas flow requires changing burner
orifice size.
Gas Supply Pressure
Gas supply pressure should be within minimum and maximum val-
ues listed on rating plate. Pressures are usually set by gas suppli-
ers.
Manifold Gas Pressure Adjustment
NOTE: Make adjustment to manifold pressure with burners operat-
ing.
!
ELECTRICAL SHOCK HAZARD.
Failure to do so can result in death, personal injury
and/or property damage.
Turn OFF power to furnace before changing speed
taps.
1.
Remove the burner compartment door.
2.
With gas OFF, connect manometer to tapped opening on
gas valve. Use manometer with a 0 to 15² water column
range.
3.
Turn gas ON and remove adjustment screw cover on gas
valve. Turn counterclockwise to decrease pressure and
clockwise to increase.
4.
For altitudes up to 2000¢, set pressure to value shown in
Table 6, ± 0.3² water column.
5.
Connect manometer to the tapped opening on the outlet
side of gas valve. Use manometer with a 0--15² min. water
column range.
6.
Turn gas ON, fire the furnace and remove adjustment screw
cover on gas valve.
7.
Turn counterclockwise to decrease pressure and clockwise
to increase.
8.
Set pressure to value shown in Table 6. Refer to Important
Notes in Table 6. Pressure is also listed on furnace rating
plate.
9.
When pressure is set, replace adjustment screw cover on
gas valve.
10. Replace the burner compartment door.
Manifold
P
Pressure
Max.
Min.
14²
4.5²
14²
11²
440 01 1020 02
3.5²
10²
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