Gas Piping
CAUTION
If a flexible gas connector is required or allowed by the authority that has jurisdiction, black iron pipe shall be installed at the gas valve and extend outside the furnace cabinet. The flexible connector can then be added between the black iron pipe and the gas supply line.
WARNING
Do not exceed 600 in−lbs (50 ft−lbs) torque when at- taching the gas piping to the gas valve.
IMPORTANT
Compounds used on threaded joints of gas piping must be resistant to the actions of liquified petro- leum gases.
Leak Check
After gas piping is completed, carefully check all piping connections (factory− and field−installed) for gas leaks. Use a leak detecting solution or other preferred means.
The furnace must be isolated from the gas supply system by closing its individual manual
1 − Gas piping may be routed into the unit through either the left- or
2 − When connecting gas supply, factors such as length of run, number of fittings and furnace rating must be con- sidered to avoid excessive pressure drop. Table 10 lists recommended pipe sizes for typical applications.
MANUAL MAIN SHUT−OFF VALVE WILL NOT HOLD NORMAL TEST PRESSURE
1/8" N.P.T. PLUGGED TAP
CAP 
FURNACE
ISOLATE GAS VALVE
NOTE − Use two wrenches when connecting gas pip- ing to avoid transferring torque to the manifold.
3 − Gas piping must not run in or through air ducts, clothes chutes, chimneys or gas vents, dumb waiters or eleva- tor shafts. Center gas line through piping hole. Gas line should not touch side of unit. See figures 47.
4 − Piping should be sloped 1/4 inch per 15 feet (6mm per 5.6m) upward toward the gas meter from the furnace. The piping must be supported at proper intervals, ev- ery 8 to 10 feet (2.44 to 3.05m), using suitable hangers or straps. Install a drip leg in vertical pipe runs to serve as a trap for sediment or condensate.
5 − A 1/8" N.P.T. plugged tap or pressure post is located on the gas valve to facilitate test gauge connection. See figure 54.
6 − In some localities, codes may require installation of a manual main
FIGURE 46
IMPORTANT
When testing pressure of gas lines, gas valve must be disconnected and isolated. See figure 46. Gas valves can be damaged if subjected to pressures greater than 1/2 psig (3.48 kPa).
WARNING
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could result in serious injury, death, or property damage. Never use an open flame to test for gas leaks. Check all connections using a commercially available soap solution made specifically for leak detection. Some soaps used for leak detection are corrosive to certain metals. Carefully rinse piping thoroughly after leak test has been completed.
Page 30
