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3
Gas connections
Combination gas valves
These units fire in multiple stages of burner input. Each stage
of burner operation has a combination gas valve(s) to cycle
the gas supply on and off and regulate gas to the burners. Each
combination valve consists of a gas regulator and two valve seats
to meet the requirements for redundant gas valves. The valve
has a gas control knob that must remain in the open position
at all times when the unit is in service. The gas control valve
has pressure taps located on the inlet and discharge sides of the
valve. Manifold pressure is adjusted using the regulator located
on the valve. A manifold gas pressure tap for each burner
stick is located on the discharge side of the valve. The manifold
pressure is preset at the factory and adjustment is not usually
required. If you must adjust regulator pressure, follow the
instructions under Gas Manifold Pressure Adjustment, page 27.
Venting of combination gas valves
The combination gas valve/regulator used on all units is
equipped with an integral vent limiting orifice per ANSI Z21.78.
The vent limiter ensures that the volume of gas emitted from
the valve in the event of a failed gas diaphragm does not exceed
the maximum safe leakage rate allowed by agency requirements.
Combination gas valve/regulators equipped with integral vent
limiters are not required to have vent or relief lines piped to
the outdoors. The termination of the vent limited opening on
the combination gas valve/regulator complies with the safety
code requirements of CSD-1, CF-190(a) as shipped from the
appliance manufacturer without the installation of additional
vent lines.
Capacity of Schedule 40 Metallic Pipe in Cubic Feet of Natural Gas Per Hour
Pipe
Size
10
20
(Inches)
1/2
131
90
3/4
273
188
1
514
353
1 1/4
1,060
726
1 1/2
1,580
1,090
2
3,050
2,090
2 1/2
4,860
3,340
3
8,580
5,900
4
17,500 12,000
26
TABLE - 3D
(based on .60 specific gravity, 0.30" w.c. pressure drop)
Length of Pipe in Straight Feet
30
40
50
60
72
62
55
N/A
151
129
114
104
284
243
215
195
583
499
442
400
873
747
662
600
1,680
1,440
1,280
1,160
2,680
2,290
2,030
1,840
4,740
4,050
3,590
3,260
9,660
8,270
7,330
6,640
Installation & Service Manual
Checking gas supply pressure
Use the following procedure to check gas supply pressure.
1. Turn the main power switch to the "OFF" position.
2. Turn gas valve knobs to the "OFF" position.
3. Shut off gas supply at the field-installed manual gas cock in
the gas piping to the unit. If fuel supply is L.P. gas, shut off
gas supply at the tank.
4. Remove the 1/8'' hex plug, located on the "inlet" side of the
gas valve (FIG. 3-3). You may also use a tapping on the
field-installed main manual gas cock or gas piping. Install a
fitting in the inlet pressure tapping suitable to connect to a
manometer or magnehelic gauge. Range of scale should be
14'' w.c. or greater to check inlet pressure.
5. Turn on gas supply at the manual gas cock, turn on L.P. gas
at the tank if required.
6. Turn the power switch to the "ON" position.
7. Turn the gas valve knobs to the "ON" position. Set the
electronic temperature control or thermostat to call for
heat.
8. Observe the gas supply pressure as all burners are firing.
Ensure that inlet pressure is within the specified range.
See Connecting To Gas Supply, page 24 for minimum and
maximum gas supply pressures.
9. If gas pressure is out of range, contact gas utility, gas
supplier, qualified installer or service agency to determine
necessary steps to provide proper gas pressure to the
control.
70
80
90
100
N/A
N/A
N/A
N/A
95
89
83
79
179
167
157
148
368
343
322
304
552
514
482
455
1,060
989
928
877
1,690
1,580
1,480
1,400
3,000
2,790
2,610
2,470
6,110
5,680
5,330
5,040
125
150
175
200
N/A
N/A
N/A
N/A
70
63
58
N/A
131
119
109
102
269
244
224
209
403
366
336
313
777
704
648
602
1,240
1,120
1,030
960
2,190
1,980
1,820
1,700
4,460
4,050
3,720
3,460
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