507713-01
Page 19 of 32
Issue 1623
Removal of the Furnace from Common Vent
In the event that an existing furnace is removed from a
venting system commonly run with separate gas appliances,
the venting system is likely to be too large to properly vent
the remaining attached appliances.
Conduct the following test while each appliance is operating
and the other appliances (which are not operating) remain
connected to the common venting system. If the venting
system has been installed improperly, you must correct the
system as indicated in the general venting requirements
section.
The following steps shall be followed for each appliance
connected to the venting system being placed into operation,
while all other appliances connected to the venting system
are not in operation:
1. Seal any unused openings in the common venting
system.
2. Inspect the venting system for proper size and horizontal
pitch. Determine that there is no blockage, restriction,
leakage, corrosion, or other deficiencies which could
cause an unsafe condition.
3. Close all building doors and windows and all doors
between the space in which the appliances remaining
connected to the common venting system are located
and other spaces of the building. Turn on clothes dryers
and any appliances not connected to the common
venting system. Turn on any exhaust fans, such as
range hoods and bathroom exhausts, so they will
operate at maximum speed. Do not operate a summer
exhaust fan. Close fireplace dampers.
4. Follow the lighting instructions. Turn on the appliance
that is being inspected. Adjust the thermostat so that
the appliance operates continuously.
5. After the burners have operated for 5 minutes, test for
leaks of flue gases at the draft hood relief opening. Use
the flame of a match or candle.
6. After determining that each appliance connected to
the common venting system is venting properly, (step
3) return all doors, windows, exhaust fans, fireplace
dampers, and any other gas burning appliances to their
previous mode of operation.
7. If a venting problem is found during any of the preceding
tests, the common venting system must be modified to
correct the problem.
Resize the common venting system to the minimum vent
pipe size determined by using the appropriate tables in
Appendix G. (These are in the current standards of the
National Fuel Gas Code ANSI 2223.1.
CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for each
appliance connected to the venting system being
placed into operation could result in carbon monoxide
poisoning or death.
WARNING
Gas Supply
1. This unit is shipped standard for left or right side
installation of gas piping (or top entry in horizontal
applications). Connect the gas supply to the piping
assembly.
2. When connecting the gas supply piping, consider factors
such as length of run, number of fittings, and furnace
rating to avoid excessive pressure drop. Table 6 lists
recommended pipe sizes for typical applications.
3. The gas piping must not run in or through air ducts,
clothes chutes, gas vents or chimneys, dumb waiters,
or elevator shafts.
4. The piping should be sloped 1/4 inch (6.4 mm) per 15
feet (4.57 m) upward toward the meter from the furnace.
The piping must be supported at proper intervals [every
8 to 10 feet (2.44 to 3.01 m)] with suitable hangers or
straps. Install a drip leg in vertical pipe runs to the unit.
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 35.
6. In some localities, codes may require the installation of
a manual main shut off valve and union (furnished by
the installer) external to the unit. The union must be of
the ground joint type.
Gas Piping
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.
CAUTION
NOTE:
If emergency shutoff is necessary, shut off the main
manual gas valve and disconnect main power to the furnace.
The installer should properly label these devices.
Compounds used on threaded joints of gas piping must
be resistant to the actions of liquified petroleum gases.
IMPORTANT
