Smith Cast Iron Boilers GB100W GAS Supply Piping, Reverse Acting Aquastats, Gas Pipe Capacity

	GB100W NATURAL OR PROPANE BOILER	Page 11
	INSTALLATION AND OPERATING INSTRUCTIONS
Reverse Acting Aquastats	GAS SUPPLY PIPING

An alternative for existing systems experiencing condensation that does not require re-piping the boiler utilizes a reverse acting aquastat, one that makes on temperature rise. This approach works best in single zone systems. Wired in series with the circulator, this control holds the circulator off until the boiler reaches an acceptable temperature and then starts system circulation, see Figure 10.

The most commonly available reverse acting aquastat is a Honeywell L4006B. The aquastat should be mounted in an immersion well directly installed in the boiler. The use of heat conductive grease, Honeywell part # 972545, in the immersion well is strongly recommended for fast and accurate temperature response. Set this adjustable aquastat to make at no less than 130° F, 54°C. While this method can cause the circulator to cycle more frequently, setting the aquastat’s differential to the maximum 25-30°F will minimize short cycling.

Figure 10: Reverse Aquastat

	115 volts
	reverse
	aquastat
	N.O.
	circulator
	24 volts
	T
	t'stat
	T
REVERSE	operating
AQUASTAT	aquastat
	GV
SET AT 120° F	N.C.

WARNING: All gas piping must be installed by a qualified technician in accordance with the provisions set forth in the latest revision of ANSI Z223.1 and all applicable local building codes and regulations. All LP gas connections must be made by a licensed propane installer. Failure to comply with this WARNING can result in extensive property damage, severe personal injury or death!

The GB100W hot water boiler comes from the factory ready to be piped to the gas supply.

WARNING: Check the boiler rating plate to make sure that the boiler is for the type of gas that will be used. If it isn’t, do not connect the boiler to the gas supply. Failure to comply with this warning can result in extensive property damage, severe personal injury or death!

If for any reason the boiler is not for the type of gas available at the installation site, call the nearest Smith Cast Iron Boiler distributor to resolve the problem.

Table 3 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 fittings. Table 4 should be used in conjunction with Table 3 to ensure that the supply piping has the capacity to meet the demand.

Table 3: Gas Pipe Capacity

Maximum pipe capacity in ft3/hr based on 0.60 specific gravity gas at pressure of 0.5 psig or less and a 0.3" W.C. pressure drop.

Nominal				Pipe length in feet
Iron Pipe	10	20	30	40	50	60	80	100	150
Size (in.)		Maximum gas volume in cubic feet/hr, (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

Table 4: Equivalent Length Chart

Eqivalent length of pipe fittings in feet

Nominal			Type of pipe fitting
Iron Pipe	90° Elbow		Tee	Gate Valve	Gas Cocks
Size		(flow thru branch) (full port)
(inches.)			Equivalent length 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