Williams 2509622 Owner's Manual page 17

Installing Your Furnace
Gas Supply and Piping (continued)
GAS PIPING
The gas supply line must be of adequate size to handle the Btu/hr.
requirements and length of the run for the unit being installed.
Determine the minimum pipe size from Figure 13, based on the
length of the run from the gas meter to the unit.
FIGURE 13 – Pipe Capacity
Pipe Capacity – Btu/hr. with Fittings
All piping must comply with local codes and ordinances or with the
National Fuel Gas Code (ANSI Z223.1 NFPA No. 54), whichever
applies. (In Canada: CAN/C.GA B149). Refer to FIGURE 14 for
the general layout of the unit. It shows the basic fittings needed.
The following rules apply:
1. Use new, properly reamed steel or black iron pipe and
fittings free of metal chips and debris that are approved by
local codes. Metal chips and debris can damage the valve.
2. Do not thread pipe too far. Valve distortion or malfunction
may result from excess pipe within the gas control valve.
Apply a moderate amount of good quality dope to the pipe
only. Leave the two end threads bare. (Figure 15). L.P.
gas installations require a dope compound resistant to the
action of liquefied petroleum gases. Excess dope going into
the valve may cause it malfunction.
3. Use ground joint unions.
4. Install a drip leg (sediment trap) to trap dirt and moisture
before it can enter the gas valve. The nipple must be a
minimum of 3-inches long.
5. Install a manual shutoff valve.
6. Provide a 1/8" NPT test gauge connection immediately
before the gas supply connection to the furnace.
FIGURE 15 – Proper Piping Practice
FIGURE 14 – Gas Piping
GAS CONNECTION
If the installation is for L.P. gas, have the L.P. installer use a two
stage regulator and make all the connections from the storage
tank.
Use two pipe wrenches when making the connection to the valve
to prevent turning and/or damage to the valve.
Connections between the manual shutoff valve and burner control
assembly can be made with an A.G.A./C.G.A. design certified
flexible connector if allowed by local codes. Drip leg and ground
joint unions are still required.
Tighten all joints securely.