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
1 - Gas piping may be routed into the unit through either the left‐ or right‐hand side. Supply piping enters into the gas valve from the side of the valve as shown in figure 57. Move Bellows grommet to side which gas line enters. Ensure opposite gas line hole is plugged with supplied plug.
IMPORTANT
When converting the ML193 unit from natural gas to LP/propane install the field provided low pressure switch. See figure 55.
LOW INLET PRESSURE SWITCH | |
| (S145) LOCATION |
Orange |
|
White | Orange |
| |
| Yellow |
| Gas Valve Shown In Off Position |
FIGURE 55
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 9 lists recommended pipe sizes for typical applications.
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 57 and 58.
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 61.
6 - In some localities, codes may require installation of a manual main shut‐off valve and union (furnished by in staller) external to the unit. Union must be of the ground joint type.
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
Never use an open flame to test for gas leaks. Check all connections using a commercially available soap solution made specifically for leak detection.
The furnace must be isolated from the gas supply system by closing its individual manual shut‐off valve during any pressure testing of the gas supply system at pressures less than or equal to 1/2 psig (3.48 kPa, 14 inches w.c.).
MANUAL MAIN
VALVE WILL NOT HOLDFURNACE NORMAL TEST PRESSURE
1/8” N.P.T. | ISOLATE | |
GAS VALVE | ||
PLUGGED TAP | ||
| ||
CAP |
|
FIGURE 56
IMPORTANT
When testing pressure of gas lines, gas valve must
be disconnected and isolated. See figure 56. 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 cer tain metals. Carefully rinse piping thoroughly after leak test has been completed.
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