46
7
Gas connections
Noble Combi Boilers 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.
2. Shut off gas supply at the manual gas valve in the gas
piping to the appliance.
WARNING
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. Adjust the temperature set point on the control panel of
the boiler control module to call for heat.
8. 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.
9. Ensure inlet pressure is within specified range.
Minimum and maximum gas supply pressures are
specified in this section of the manual.
10. If gas supply pressure is within normal range and no
adjustments are needed, proceed on to Step 11.
11. 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.
12. Exit Service Mode.
13. 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
F I R E T U B E C O M B I
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