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All pipe joint compound must be resistant to the action of L.P. gas. When connecting the gas service
to the furnace, install a ground union joint and manual shutoff exterior to the furnace cabinet. This
permits the control assembly to be easily removed. A 1/8" NPT plug on the supply pipe at the manual
valve for the purpose of making pressure measurement must also be installed. The valve should be
readily accessible for turning on or off. A capped drip leg must be installed in the gas supply pipe as
close to the furnace as possible. The drip leg should be installed so that it incorporates a change of
direction.
Refer to local codes or the above mentioned publications for proper location of the manual shutoff
and drip leg lengths. The gas pipe must be sized to eliminate undue pressure drop. See pipe
capacity table or consult your local utility. When checking the manifold pressure, use the pressure tap
located on the gas valve. When checking the service pressure, use the field installed tap located on
the manual shut-off or supply pressure tap located on the gas valve.
All gas piping must conform to local codes, or in the absence of local codes, to the National Fuel Gas
Code ANSI Z223.1 and / or CAN/CGA B149 Installation Codes.
NOTE: Copper tubing must not be used for natural gas installations where more than .3 grains of
hydrogen sulfide per 100 standard cubic feet of gas is present.
For installations in the Commonwealth of Massachusetts see Fuel Gas and Plumbing Code 248
CMR: Appendix C.
Capacity of gas pipe of different diameters and length in ft
a specific gravity of 0.60 (natural gas).
*PIPE
SIZE
1/2
3/4
1
1 1/4
1 1/2
* Nominal size of Iron Pipe in inches.
After the length of pipe has been determined, select the pipe size which will provide the minimum
cubic per hour of gas flow for the required input of the appliance. In the case where more than one
appliance utilizes the same supply pipe be sure to consider the sum of all appliances. The cubic feet
required for the appliances should be determined using the following formula;
Cubic feet of gas required = Gas input of appliance (Btu/hr) / heating value of gas(Btu/hr)
The gas input of the appliance is marked on the specification plate. The heating value of the gas may
be determined by contacting the gas utility or gas supplier. The GSM furnace is a two stage furnace
with the first stage delivering approximately 60% of the total furnace input.
IO-176
LENGTH OF PIPE IN FEET
10
20
30
132
92
73
278
190
152
520
350
285
1050 730
590
1600 1100 890
3
/hr, with a pressure drop of 0.3" W.C. and
40
50
60
70
63
56
50
130
115 105
245
215
195 180
500 440
400 370
760 670
610 560
14
80
46
43
96
90
170
350
530
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