Smith Cast Iron Boilers GT Series manual Gas Supply Piping, Gas Pipe Capacity

Page 18 GT INSTALLATION AND OPERATION INSTRUCTIONS

GAS SUPPLY PIPING

The GT hot water boiler comes from the factory ready to be piped to the gas supply. The National Fuel Gas Code, ANSI Z223.1/NFPA 54 and local codes for gas piping requirements and sizing must be followed. If for any reason the boiler is not for the type of gas available at the installation site, call the nearest Smith distributor to resolve the problem.

Figure 27 depicts the proper way to connect the boiler to the gas supply piping.The manual shut-off valve MUST be installed in the supply piping. It should be approximately 5 ft, 1.5 m, above the floor. Provide a sediment trap/drip leg at the bottom of the vertical section of the gas supply pipe. A ground joint union should be installed between the boiler gas controls and the supply piping. Each of these items is needed to ensure long life and ease of servicing. Always use a pipe sealant that is suitable for use with LP gas. Flexible gas piping is recommended if accepted by the local codes. Make sure the gas piping doesn’t hinder boiler access.

CAUTION: Always use a wrench on the gas valve body when making gas connections to it. Never over- tighten the piping entering the gas valve body or the gas valve will be damaged voiding the warranty!

CAUTION: The gas piping must be properly supported by the building structure and not by the boiler or the gas valve will be damaged voiding the warranty!

Figure 27 - Gas Supply Piping

Table 4 should be used to ensure that the gas supply piping is sized properly. If more than one appliance is supplied by the same supply pipe, the piping must be sized based on the maximum possible demand. Do not neglect the pressure drop due to pipe fi ttings. Table 5 should be used in conjunction with Table 4 to ensure that the gas supply piping is sized properly.

Safe lighting and other performance criteria were met with the gas manifold and control assembly provided on the boiler when the boiler underwent tests specifi ed in ANSI Z21.13/CSA 4.9. All gas connections MUST be leak tested before putting the boiler into operation.

WARNING: Never use an open flame to test for gas leaks. Always use an approved leak detection method. Failure to comply with this WARNING could result in an explosion!

Table 4 - Gas Pipe Capacity

Nominal				Pipe Length
Iron Pipe	10'	20'	30'	40'	50'	60'	80'	100'	150'
Size			Gas Pipe Capacity (ft3/hr)
3/4"	278	190	152	130	115	105	90	79	64
1"	520	350	285	245	215	195	170	150	120
1 1/4"	1050	730	590	500	440	400	350	305	250
1 1/2”	1600	1100	890	760	670	610	530	460	380

Note: Maximum pipe capacity in ft3/hr is based on a 0.60 specific gravity

gas at a pressure of 0.5 psig and a 0.3" WC pressure drop.

Table 5 - Equivalent Pipe Length Chart

Nominal			Type of Pipe Fitting
Iron		90°	Tee	Gate Valve	Gas Cocks
Pipe			(branch flow)	(full port)
Size		Equivalent length of pipe fittings in feet
3/4"		2.06	4.12	0.48	1.25
	1"	2.62	5.24	0.61	1.60
1	1/4"	3.45	6.90	0.81	2.15
1	1/2"	4.02	8.04	0.94	2.50

Whenever the gas supply piping is pressure tested the boiler gas controls must be protected. If the test pressure is equal to, or less than 1/2 psi, 3.5 kPa, isolate the boiler by closing it’s manual shut off valve, see Figure 27. If the test pressure is greater than 1/2 psi, 3.5 kPa, disconnect the boiler and it’s individual shut-off valve from the gas supply piping.

WARNING: Failure to protect the gas valve from excessive pressure can damage the gas valve which can cause a fire or explosion!