High Altitude Adjustment - Williams 1773512 Installation Instructions And Owner's Manual

Check all local codes for requirements, especially for the size and type of gas supply line required. On natural gas lines less than
15" (380 mm) long, use 1/2" tube; on longer runs, use 3/4" iron tube or equal. On LP Gas lines please consult LP Gas supplier.
Installing a New Main Gas Shutoff Valve
Each furnace should have its own manual gas shutoff valve. A manual main gas shutoff valve should be located in the vicinity of
the furnace. Where none exists, or where its size or location is not adequate, contact your local authorized installer for
installation or relocation.
Compounds used on threaded joints of gas piping must be resistant to the action of LP Gas. The gas lines must be checked for
leaks by the installer. This should be done with a soap solution watching for bubbles on all exposed connections, and if
unexposed, a pressure test should be made. Correct all gas leaks before operating the furnace.
Never use an exposed flame to check for leaks. The furnace must be disconnected from piping at inlet of control valve
and pipe capped or plugged for a pressure test. Never pressure test with furnace connected; the control valve will
sustain damage!
A gas shutoff valve and ground joint union should be installed in the gas line upstream of the gas control valve to aid in
servicing. It is required by the National Fuel Gas Code that a drip line be installed near the gas inlet. This should consist of a
vertical length of pipe tee connected into the gas line that is capped on the bottom in which condensation and foreign particles
may collect.
Use of the following gas connectors is recommended:
– ANSI Z21.24 Appliance Connectors of Corrugated Metal Tubing and Fittings., CGA 6.10.
– ANSI Z21.45 Assembled Flexible Appliance Connectors of Other Than All–Metal Construction.
The above connectors may be used if accepted by the authorities having jurisdiction.
Pressure Testing of the Gas Supply System
1. To check the inlet pressure to the gas valve, a plugged tapping, accessible for a test gauge connection, is provided on the
gas valve. (Figure 8 - A).
2. The furnace and its individual shutoff valve must be disconnected from the gas supply piping system during any pressure
testing of that system at test pressures in excess of 1/2 psig (3.5 kPa).
3. The furnace must be isolated from the gas supply piping system by closing its individual manual shutoff valve during any
pressure testing of the gas supply piping system at test pressures equal to or less than 1/2 psig (3.5 kPa).
Attention: If one of the above procedures results in pressures in excess of 1/2 psig (14" w.c.; 3.5 kPa) on the furnace gas valve,
it will result in a hazardous condition.
High Altitudes (US Only)
For altitudes/elevations above 2,000 feet (610 m), ratings should be reduced at the rate of 4-percent for each 1,000 feet (305 m)
above sea level by reducing the manifold pressure at 8% rate on the gas supply. Maximum altitude allowed for installation is
5,500 feet (1680 m).
High Altitudes (Canada Only)
The furnace is tested according to CGA 2.17 M91 for installation between 0 and 4,500 ft (0 and 1370 m) altitude. For
altitudes/elevations above 2,000 feet (610 m), ratings should be reduced at the rate of 4-percent for each 1,000 feet (305 m)
above sea level by reducing the manifold pressure at 8% rate on the gas supply. Maximum altitude allowed for installation is
5,500 feet (1680 m).

High Altitude Adjustment

Based on the altitude of the installation site, reduce the manifold pressure specified in the "Technical Data" chart and as shown
in the table below:
Gas Supply
Manifold Pressure
Altitude Reduction Rate
0-2,000 ft
2,000-3,000 ft
3,000-4,000 ft
4,000-5,000 ft
5,000-5500 ft
0%
8%
16%
24%
32%
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