8
Figure 9: Pilot and Gas Piping, Intermittent Ignition
(EI)
Figure 8: Pilot and Gas Piping, Continuous Ignition
(Standing Pilot)
IV. Gas Piping
A.
Size gas piping.
Design system to provide adequate gas
supply to boiler. Consider these factors:
1. Allowable pressure drop from point of delivery to
boiler. Maximum allowable system pressure is ½
psig. Actual point of delivery pressure may be less;
contact gas supplier for additional information.
Minimum gas valve inlet pressure is listed on rating
label.
2. Maximum gas demand. Table 4 lists boiler input
rate. Also consider existing and expected future gas
utilization equipment (i.e. water heater, cooking
equipment).
3. Length of piping and number of fittings. Refer to
Table 5 for maximum capacity of Schedule 40 pipe.
Table 6 lists equivalent pipe length for standard
fittings.
4. Corrections for the specific gravity of natural gas
can be found in Table 7.
For materials or conditions other than those listed
above, refer to
National Fuel Gas Code
, NFPA
54/ANSI Z223.1, or size system using standard
engineering methods acceptable to authority having
jurisdiction.
B
. Connect boiler gas valve to gas supply system.
1. Use methods and materials in accordance with local
plumbing codes and requirements of gas supplier. In
absence of such requirements, follow
National Fuel
Gas Code
, NFPA 54/ANSI Z223.1.
2. Use thread (joint) compounds (pipe dope) resistant
to action of liquefied petroleum gas.
3. Install sediment trap, ground-joint union and manual
shut-off valve upstream of boiler gas control valve.
See Figure 8 or 9.
4. All above ground gas piping upstream from manual
shut-off valve must be electrically continuous and
bonded to a grounding electrode. Do not use gas
piping as grounding electrode. Refer to
National
Electrical Code
, ANSI/NFPA 70.
Table 4: Rated Input
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