Slant/Fin Gas Hot Water - Manual (Page 10)

10
Gas Main Sizing
To determine the correct pipe diameter for the gas main serving a specific Caravan
system, proceed as follows:
a. Follow the building plans, find total length of straight pipe between supply from gas
meter and boiler gas header.
b. Using data in Table 4, calculate equivalent linear length of screw pipe fittings used in
fabrications of main. Add this to figure from step (a) to obtain equivalent total length.
c. Find Caravan gas consumption in cubic feet per hour from Table 3 in hot water
systems.
d. Multiply the system total hourly gas consumption by flow correction value from
Table 5.
e. Locate system’s total equivalent pipe length in right column of Table 6.
f. Move vertically to the system’s corrected flow rate calculated in step (c). If this value
falls between two of those listed, select larger value.
g. From this point move horizontally to the left column and read suggested pipe
diameter for gas main.
GGT-600E 600
GGHT-700E 700
GGHT-750E 750
GGHT-800E 798
GGT-900E 900
GGHT-1050E 1050
GGHT-1125E 1125
GGHT-1200E 1197
GGT-1200E 1200
GGHT-1400E 1400
GGHT-1500E 1500
GGT-1500E 1500
GGHT-1600E 1596
GGHT-1750E 1750
GGHT-1875E 1875
GGHT-2000E 1995
GGHT-2100E 2100
GGHT-2250E 2250
GGHT-2400E 2394
GGHT-2450E 2450
GGHT-2625E 2625
GGHT-2800E 2793
GGHT-2800AE 2800
GGHT-3000E 3000
GGHT-3150E 3150
GGHT-3200E 3192
GGHT-3375E 3375
GGHT-3500E 3500
GGHT-3600E 3591
GGHT-3750E 3750
GGHT-4000E 3990
1/2 0.84 0.52 0.41 0.031 2.50 1.12 1.25 1.66
3/4 1.17 0.73 0.57 0.044 3.50 1.84 1.75 2.33
1 1.57 0.98 0.77 0.057 4.68 2.11 2.34 3.11
1-1/4 2.19 1.37 1.07 0.082 6.54 2.94 3.27 4.35
1-1/2 2.63 1.64 1.29 0.098 7.84 3.52 3.92 5.21
2 3.55 2.23 1.74 1.320 10.60 4.77 5.30 7.05
3 5.72 3.59 2.81 2.130 17.08 7.69 8.84 11.40
Model No.
Gas
Consumption In CFH
Table 3: Gas consumption rate
hot water boilers only
Table 4: Equivalent linear length in feet of standard iron pipe fittings for natural gas
Figure 11. Typical gas supply line installation
Pipe
Size
Inches Standard
Medium
Sweep
Long
Sweep Gate Globe Angle
Return
Bend
Side
Outlet
Tee
Elbow Valve
GAS PIPING
This section contains sizing and construction recommendations
for fuel supply piping to Caravan gas-fired modular boiler
systems. Gas-fired equipment must conform not only to codes of
local regulatory agencies, but also to additional specifications that
may be imposed by the utility or gas supplier. Therefore, the
following information should be considered only as a guideline.
Figure 11 illustrates a typical gas supply line installation. It
consists of a main between the utility’s meter box and the boiler
system, a main shut-off valve sediment trap, gas header pipe and
drip legs on individual boilers.
Individual gas lines to individual boiler modules should be 3 ⁄
4
"
diameter. Size of gas main and header pipes depends on volume
of gas required and acceptable pressure drop between meter and
modules’ gas regulator valves. Minimum pressure required at each
valve is 5 inches of water column for natural gas and 11 inches for
propane gas, measured while all boilers and other gas-fired
equipment on the same meter are firing. Small variations in gas
flow can be compensated for by adjusting gas regulator valves.
However, final pressure of gas header must vary no more than
+ 0.3 in. of water column.