Reznor RPBL Unit Installation Manual - Manual (Page 14)

Form I-SSCBL/RPBL, Page 14
Sizing Gas Supply Lines
Manifold or Orifice
(Valve Outlet) Pressure
Settings
6.0 Mechanical
(cont'd)
6.1 Gas Piping
and Pressures
(cont'd)
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" 1-1/4" 1-1/2" 2" 2-1/2"
Natural Propane Natural Propane Natural Propane Natural Propane Natural Propane
20' 350 214 730 445 1100 671 2100 1281 3300 2013
30' 285 174 590 360 890 543 1650 1007 2700 1647
40' 245 149 500 305 760 464 1450 885 2300 1403
50' 215 131 440 268 670 409 1270 775 2000 1220
60' 195 119 400 244 610 372 1105 674 1850 1129
70' 180 110 370 226 560 342 1050 641 1700 1037
80' 170 104 350 214 530 323 990 604 1600 976
90' 160 98 320 195 490 299 930 567 1500 915
100' 150 92 305 186 460 281 870 531 1400 854
125' 130 79 275 168 410 250 780 476 1250 763
150' 120 73 250 153 380 232 710 433 1130 689
175' 110 67 225 137 350 214 650 397 1050 641
200' 100 61 210 128 320 195 610 372 980 598
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.
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 follow-
ing warnings and instructions apply.
For Natural Gas: When the heater leaves the factory, the combination valve is set so
that the outlet gas pressure of a single-stage valve or high fire of a two-stage valve is
regulated to 3.5" w.c. Low fire on a two-stage valve is set to 1.8" w.c. Inlet supply pres-
sure to the valve must be a minimum of 5" w.c. or as noted on the rating plate and a
maximum of 14" w.c. NOTE: Always check the rating plate for minimum gas sup-
ply pressure. Minimum supply pressure requirements vary based on size of burner
and the gas control option. Most units require a minimum of 5" w.c. of natural gas as
stated above, but larger sizes with electronic modulation require a minimum of 6" w.c.
natural gas supply pressure.
For Propane: When the heater leaves the factory, the combination valve is set so that
the outlet gas pressure of a single-stage valve or high fire of a two-stage valve is 10"
w.c. Low fire on a two-stage valve is set to 5" w.c. Inlet pressure to the valve must be
a minimum of 11" w.c. and a maximum of 14" w.c.
Before attempting to measure or adjust manifold gas pressure, the inlet (supply) pres-
sure must be within the specified range for the gas being used both when the heater is
in operation and on standby. Incorrect inlet pressure could cause excessive manifold
gas pressure immediately or at some future time.
Instructions to Check Valve Outlet (Manifold) Pressure:
1) With the manual valve (on the combination valve) positioned to prevent flow to the
main burners, connect a manometer to the 1/8" pipe outlet pressure tap in the valve.
NOTE: A manometer (fluid-filled gauge) is recommended rather than a spring type
gauge due to the difficulty of maintaining calibration of a spring type gauge.
2) Open the valve and operate the heater. Measure the gas pressure to the manifold.
To measure the low stage pressure on units equipped with a two-stage valve, discon-
nect the wire from the "HI" terminal on the valve. (Be sure to reconnect the wire.)
Normally adjustments should not be necessary to the factory preset regulator. If adjust-
ment is necessary, set pressure to correct settings by turning the regulator screw IN
(clockwise) to increase pressure. Turn regulator screw OUT (counterclockwise) to
decrease pressure. Consult the valve manufacturer's literature provided with the fur-
nace for more detailed information.
CAUTION: DO NOT bottom out the gas valve regulator adjusting
screw. This can result in unregulated manifold pressure causing
overfire and heat exchanger failure.