50
Installation & Operation Manual
7
Gas connections
Knight 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 orifice (see page 13).
In order to operate on LP gas, an orifice 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. Turn the main power switch to the “OFF” position.
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. 7-4.
4. Slowly turn on the gas supply at the field installed
manual gas valve.
5. Turn the power switch to the “ON” position.
6. Adjust the temperature set point on the control panel of
the SMART SYSTEM control module to call for heat.
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 11.
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. Turn the power switch to the “OFF” position.
12. Shut off the gas supply at the manual gas valve in the gas
piping to the appliance.
13. Remove the manometer from the pressure tap on top of
the gas valve. Re-tighten the set screw inside the pressure
tap.
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
