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A. Allowable loss of pressure to assure a burner
manifold pressure of 3½" (8.9cm) water for natural
gas.
B. Supply of gas to be provided in cubic feet.
C. Length of piping and number of ttings.
D. Specic gravity of gas.
E. Correction factor for specic gravity.
9. BOILER PIPING
CAUTION
Failure to properly pipe boiler may result in
improper operation and damage to boiler or
building.
A. CLEARANCES - Hot water pipes do not require
clearance from combustible construction.
B. Install drain valve and safety relief valve as shown
in Figures 1 and 3. Note - Safety relief valve must
be in vertical position.
C. Pipe safety relief valve discharge to oor.
Table 1: Maximum Capacity of Schedule 40 Pipe in CFH For Natural Gas Pressures of ½ psig or Less
Table 2: Equivalent Length of Fittings
Table 3: Specic Gravity Correction Factors for
Natural Gas
This piping is to be supplied by the installer and must
include a trap, a ground joint union and a manual
shutoff valve upstream of the gas control assembly
outside of the jacket when codes require, see Figure 1.
A pipe thread compound resistant to the action of
liqueed petroleum gases should be applied to all
threaded joints in the gas piping. Pressure testing of the
Gas Supply Piping Boiler and its connections is
required before placing the boiler in operation.
The boiler and shutoff valve must be disconnected from
the gas supply piping system during any pressure
testing at pressures greater than ½ psig (3.5kPa).
The boiler must be isolated from the gas supply piping
system by closing its individual manual shutoff valve
during any pressure testing of the gas supply piping
system at pressures equal to or less than ½ psig
(3.5kPa).
RECOMMENDED SIZING OF GAS SUPPLY
PIPING TO BOILER FOR NATURAL GAS - shall
be such as to provide the required supply of gas without
undue loss of pressure between meter and the boiler.
Gas supply piping should be sized in accordance with
the Tables 1, 2 and 3. The following shall be taken into
account:
Length
[Feet]
0.3 Inch w.c. Pressure Drop 0.5 Inch w.c. Pressure Drop
½ ¾ 1 1¼ ½ ¾ 1 1¼
10 132 278 520 1,050 175 360 680 1,400
20 92 190 350 730 120 250 465 950
30 73 152 285 590 97 200 375 770
40 63 130 245 500 82 170 320 660
50 56 115 215 440 73 151 285 580
60 50 105 195 400 66 138 260 530
70 46 96 180 370 61 125 240 490
80 43 90 170 350 57 118 220 460
90 40 84 160 320 53 110 205 430
100 38 79 150 305 50 103 195 400
Fitting
Nominal Pipe Size
½ ¾ 1 1¼
45° Ell 0.7 1 1.2 1.6
90° Ell 1.6 2.1 2.6 3.5
Tee (As Elbow) 3.1 4.1 5.2 6.9
Specic
Gravity
Correction
Factor
Specic
Gravity
Correction
Factor
0.50 1.10 1.30 1.07
0.55 1.04 1.40 1.04
0.60 1.00 1.50 1.00
0.65 0.96 1.60 0.97
0.70 0.93 1.70 0.94
0.75 0.90 --- ---
0.80 0.87 --- ---