Reznor SC Duct Furnace Unit Installation Manual - Manual (Page 8)

Form I-SC, P/N 207696 R11, Page 8
6.2 Gas Piping and
Pressures
Gas Connection
Sizing Gas Supply
Lines
WARNING
This appliance is equipped for a maximum gas supply pressure of 1/2 psi, 3.5 kPa,
or 14 inches water column. NOTE: Supply pressures higher than 1/2 psi require
installation of an additional service regulator external to the unit.
Pressure Testing Supply Piping
Test Pressure Above 1/2 PSI: Disconnect the heater and manual valve from the gas
supply which is to be pressure tested. Cap or plug the supply line.
Test Pressure Below 1/2 PSI: Before testing, close the manual valve on the heater.
WARNING
Manifold gas pressure must never exceed 3.5" w.c. for natural gas or
10" w.c. for propane gas.
All piping must be in accordance with requirements outlined in the National Fuel
Gas Code ANSI/Z223.1 (latest edition) or CSA B149.1 and B149.2 (See Paragraph
1.4.) Gas supply piping installation should conform with good practice and with local
codes.
These separated-combustion units for natural gas are orificed for gas having a heating
value of 1000 (±50) BTU per cubic ft. If the gas at the installation does not meet this
specification, consult the factory for proper orificing.
Seal the opening for the gas supply pipe with the grommet provided.
Pipe joint compounds (pipe dope) shall be resistant to the action of liquefied petroleum
gas or any other chemical constituents of the gas being supplied.
Install a ground joint union and manual shutoff valve upstream of the unit control sys-
tem. The 1/8" plugged tapping in the shutoff valve provides connection for supply line
pressure test gauge. The National Fuel Gas Code requires the installation of a trap
with a minimum 3" drip leg. Local codes may require a longer drip leg, typically 6".
WARNING
All components of a gas supply system must be leak tested prior to
placing the equipment in service. NEVER TEST FOR LEAKS WITH AN
OPEN FLAME. See Hazard Levels, page 2.
Model SC Sizes 100-250 300-400
Natural Gas 1/2" 3/4"
Propane 1/2" 1/2"
NOTE: The above are gas connection
sizes; not supply line sizes.
After all connections are made, discon-
nect the pilot supply at the control valve
and bleed the system of all air. Reconnect
the pilot line and leak test all connections
by brushing on a soap solution.
Capacity of Piping
Cubic Feet per Hour based on 0.3" w.c. Pressure Drop
Specific Gravity for Natural Gas -- 0.6 (Natural Gas -- 1000 BTU/Cubic Ft)
Specific Gravity for Propane Gas -- 1.6 (Propane Gas -- 2550 BTU/Cubic Ft)
Length
of Pipe
Diameter of Pipe
1/2" 3/4" 1" 1-1/4" 1-1/2" 2"
Natural Propane Natural Propane Natural Propane Natural Propane Natural Propane Natural Propane
20' 92 56 190 116 350 214 730 445 1100 671 2100 1281
30' 73 45 152 93 285 174 590 360 890 543 1650 1007
40' 63 38 130 79 245 149 500 305 760 464 1450 885
50' 56 34 115 70 215 131 440 268 670 409 1270 775
60' 50 31 105 64 195 119 400 244 610 372 1105 674
70' 46 28 96 59 180 110 370 226 560 342 1050 641
80' 43 26 90 55 170 104 350 214 530 323 990 604
90' 40 24 84 51 160 98 320 195 490 299 930 567
100' 38 23 79 48 150 92 305 186 460 281 870 531
125' 34 21 72 44 130 79 275 168 410 250 780 476
150' 31 19 64 39 120 73 250 153 380 232 710 433
175' 28 17 59 36 110 67 225 137 350 214 650 397
200' 26 16 55 34 100 61 210 128 320 195 610 372
Note: When sizing supply lines, consider possibilities of future expansion and increased requirements.
Refer to National Fuel Gas Code for additional information on line sizing.
Manifold or Orifice
(Valve Outlet) Pressure
Settings
Measuring manifold gas pressure cannot be done until the heater is in operation. It
is included in the steps of the "Check-Test-Start" procedure in Paragraph 9.0. The
following warnings and instructions apply.
6.0 Mechanical
(cont'd)