Install Instructions

52
7 Gas connections
Noble Fire Tubes are typically shipped ready to fire on natural gas. Check boiler rating plate to determine
which fuel the boiler is set for. If set to natural gas, it may be converted to LP by installing an LP venturi (see
page 12). In order to operate on LP gas, an LP venturi MUST BE installed. Failure to comply could result
in severe personal injury, death, or substantial property damage.
Table 7A Natural Gas Pipe Size Chart
The gas piping must be sized for the proper flow and length
of pipe, to avoid excessive pressure drop. Both the gas
meter and the gas regulator must be properly sized for the
total gas load.
If you experience a pressure drop greater than 1 inch w.c.,
the meter, regulator, or gas line is undersized or in need of
service. Perform the steps below when checking inlet gas
supply:
1. Shut OFF power at source.
⚠WARNING
2. Shut off gas supply at the manual gas valve in the gas
piping to the appliance.
3. Loosen the set screw one (1) full turn from inside the
pressure tap on top of the gas valve. Place the tubing of
the manometer over the tap once the set screw is
loosened as shown in FIG. 7-3.
4. Slowly turn on the gas supply at the field installed
manual gas valve.
5. Turn ON power at source.
6. Press and hold the RIGHT and DOWN buttons
simultaneously for five (5) seconds to place the boiler into
Service Mode. In Service Mode, the boiler will fire at
ignition speed and will then modulate up to full fire.
7. Observe the gas supply pressure as the burner fires at
100% of rated input. Percent of burner input will be
displayed on the control panel.
8. Ensure inlet pressure is within specified range.
Minimum and maximum gas supply pressures are
specified in this section of the manual.
9. If gas supply pressure is within normal range and no
adjustments are needed, proceed on to Step 10.
10. If the gas pressure is out of range, contact the gas utility,
gas supplier, qualified installer or service agency to
determine the necessary steps to provide proper gas
pressure to the control.
11. Exit Service Mode.
12. Turn OFF power at source.
Check inlet gas supply
NOTICE
CSA or UL listed flexible gas connections
are acceptable, but you must exercise
caution to ensure that the line has
adequate capacity to allow your boiler
to fire at full rate. Consult with local
codes for proper installation or service
procedures.
DO NOT adjust gas valve outlet
pressure. The gas valve is factory-set
for the correct outlet pressure. This
setting is suitable for natural gas and
propane, requiring no field adjustment.
Attempting to alter the gas valve outlet
pressure could result in damage to the
valve, causing potential severe personal
injury, death, or substantial property
damage.
⚠WARNING
Capacity of Schedule 40 Metallic Pipe in Cubic Feet of Natural Gas Per Hour
(based on .60 specific gravity, 0.30" w.c. pressure drop)
Pipe
Size
(Inches)
Length of Pipe in Straight Feet
10 20 30 40 50 60 70 80 90 100 125 150 175 200
1/2 131 90 72 62 55 N/A N/A N/A N/A N/A N/A N/A N/A N/A
3/4 273 188 151 129 114 104 95 89 83 79 70 63 58 N/A
1 514 353 284 243 215 195 179 167 157 148 131 119 109 102
1 1/4 1,060 726 583 499 442 400 368 343 322 304 269 244 224 209
1 1/2 1,580 1,090 873 747 662 600 552 514 482 455 403 366 336 313
2 3,050 2,090 1,680 1,440 1,280 1,160 1,060 989 928 877 777 704 648 602
2 1/2 4,860 3,340 2,680 2,290 2,030 1,840 1,690 1,580 1,480 1,400 1,240 1,120 1,030 960
3 8,580 5,900 4,740 4,050 3,590 3,260 3,000 2,790 2,610 2,470 2,190 1,980 1,820 1,700
4 17,500 12,000 9,660 8,270 7,330 6,640 6,110 5,680 5,330 5,040 4,460 4,050 3,720 3,460
Installation & Service Manual
FIRE TUBE
™
NOTICE
For more details and additional sizing charts, reference the National Fuel Gas Code.