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Installer’s Guide
18-CD21D1-5 21
▲
CAUTION
!
Replace and/ or tighten all plugs removed or loosened
when adjusting gas pressure. Leak check the fittings
before placing the furnace into regular service.
Failure to follow this warning could result in fire, ex-
plosion, or property damage.
For LP gases, the final manifold pressure setting shall
be 10.5" W.C. with an input of no more than the name-
plate rating and no less than 93% of the nameplate rat-
ing, unless the unit is derated for altitude.
Table 10 lists the main burner orifices shipped with the
furnace. If a change of orifices is required to correct the
input rate, refer to Table 11.
TABLE 9
NATURAL GAS ONLY
TABLE OF CUBIC FEET PER HOUR OF GAS
FOR VARIOUS PIPE SIZES AND LENGTHS
PIPE
SIZE
LENGTH OF PIPE
10 20 30 40 50 60 70
1/2 132 92 73 63 56 50 46
3/4 278 190 152 130 115 105 96
1 520 350 285 245 215 195 180
1-1/4 1050 730 590 520 440 400 370
This table is based on pressure drop of 0.3 inch W.C. and 0.6 SP.GR. gas
TABLE 10
ORIFICE SIZES
INPUT
RATING
BTUH
NUMBER
OF
BURNERS
MAIN BURNER ORIFICE
DRILL SIZE
NAT. GAS LP GAS
40,000
60,000
80,000
100,000
120,000
140,000
2
3
4
5
6
7
45
45
45
45
45
45
56
56
56
56
56
56
TABLE 11
PART NUMBERS FOR REPLACEMENT ORIFICES
DRILL
SIZE
PART
NUMBER
DRILL
SIZE
PART
NUMBER
44
45
46
47
48
49
50
ORF00501
ORF00644
ORF00909
ORF00910
ORF01099
ORF00503
ORF00493
54
55
56
57
58
59
ORF00555
ORF00693
ORF00907
ORF00908
ORF01338
ORF01339
HIGH ALTITUDE DERATE
Input ratings (BTUH) of these furnaces are based on
sea level operation and should not be changed at eleva-
tions up to 2,000 ft.
If the installation is 2,000 ft. or above, the furnace input
rate (BTUH) shall be reduced 4% for each 1,000 ft.
above sea level. The furnace input rate shall be checked
by clocking the gas flow rate (CFH) and multiplying by
the heating value obtained from the local utility sup-
plier for the gas being delivered at the installed altitude.
Input rate changes can be made by adjusting the mani-
fold pressure (min 3.0 - max 3.7 in. W.C. - Natural Gas)
or changing orifices (orifice change may not always be
required). If the desired input rate cannot be achieved
with a change in manifold pressure, then the orifices
must be changed. LP installations will require an orifice
change.
Installation of this furnace at altitudes above 2,000 ft.
(610m) shall be in accordance with local codes, the Na-
tional Fuel Gas Code, ANSI Z223.1/ NFPA 54 or Na-
tional Standard of Canada, Natural Gas and Propane
Installation Code, CSA B149.1. Installation of this fur-
nace at altitudes above 2,000 ft. (610m) shall be made in
accordance with the listed high Altitude Conversion Kit
available with this furnace.
IMPORTANT:
Re-install the propane orifices to the same depth as the
orifices supplied with the equipment.
See Table 13 for help in selecting orifices if orifice
change is required. Furnace input rate and tempera-
ture rise should be checked again after changing ori-
fices to confirm the proper rate for the altitude.
Installations above 4,000 feet may require a pressure
switch change. If required, use the BAYHALT*** Kit
(High Altitude Accessory Kit) listed in PRODUCT DATA.
▲
WARNING
!
EXPLOSION HAZARD!
PROPANE GAS IS HEAVIER THAN AIR AND MAY
COLLECT IN ANY LOW AREAS OR CONFINED
SPACES. IN ADDITION, ODORANT FADE MAY MAKE
THE GAS UNDETECTABLE EXCEPT WITH A WARN-
ING DEVICE. IF THE GAS FURNACE IS INSTALLED
IN A BASEMENT, AN EXCAVATED AREA OR A
CONFINED SPACE, IT IS STRONGLY RECOM-
MENDED TO CONTACT A GAS SUPPLIER TO IN-
STALL A GAS DETECTING WARNING DEVICE IN
CASE OF A GAS LEAK.
NOTE: The manufacturer of your furnace does NOT test
any detectors and makes no representations regarding
any brand or type of detector.