Installation Manual

7
Direct Vent Installation
This condensing furnace is certified for installation as
a Direct Vent (2-pipe) appliance. Direct Vent (2-pipe)
furnaces draw combustion air directly from the outdoors
and then vent the combustion products back outside,
isolating the entire system from the indoor space. It is
important to make sure that the whole system is sealed
and clearances to combustibles are maintained regardless
of the installation being in a confined or unconfined space.
This section specifies installation requirements for Direct
Vent (2-pipe) piping. Table 2, (page 8) contains the
length of vent and combustion air piping for this type of
installation.
Provisions must be made during the installation of this
furnace that provide an adequate supply of fresh air for
combustion and ventilation. The combustion air from the
outside needs to be clear of chemicals that can cause
corrosion. The inlet pipe should not be placed near
corrosive chemicals such as those listed on page 5.
Air openings on top of the furnace and openings in closet
doors or walls must never be restricted. If the furnace is
operated without adequate air for combustion, the flame
roll-out switch will open, turning off the gas supply to the
burners. This safety device is a manually reset switch.
DO NOT install jumper wires across these switches
to defeat their function or reset a switch without
identifying and correcting the fault condition. If a
switch must be replaced, use only the correct sized part
specified in the Replacement Parts List provided online.
Vent Pipe Length & Diameter
For proper furnace operation, the combustion air and vent
piping must not be excessively restrictive.
• The venting system should be designed to have the
minimum number of elbows or turns.
• All horizontal runs must slope upwards from the furnace
at 1/4 inch minimum per running foot of vent.
• Transition to the final vent diameter should be done as
close to the furnace outlet as practical.
• Always use the same size or a larger pipe for combustion
air that is used for the exhaust vent.
Table 2 indicates the maximum allowable pipe length for
a furnace of known input rate, when installed with piping
of selected diameter and number of elbows. To use the
table, the furnace input rate, the centerline length and the
number of elbows on each pipe must be known.
When estimating the length of vent runs, consideration
must be made to the effect of elbows and other fittings.
This is conveniently handled using the idea of “equivalent
length”. This means the fittings are assigned a linear length
that accounts for the pressure drop they will cause. For
example: a 3” diameter, long radius elbow is worth the
equivalent of 3.5 feet of linear run.
The equivalent lenghts of tees and various elbows are
listed in Table 2. Measure the linear length of your vent run
and then add in the equivalent length of each fitting. The
total length, including the equivalent fitting lengths, must
be less than the maximum length specified in the table.
Important Information
WARNING:
Furnace installation using methods other than
those described in the following sections must
comply with the National Fuel Gas Code (NFGC)
and all applicable local codes.
WARNING:
Upon completion of the furnace installation,
carefully inspect the entire flue system both
inside and outside the furnace to assure it is
properly sealed. Leaks in the flue system can
result in serious personal injury or death due
to exposure of flue products, including carbon
monoxide.
WARNING:
This furnace must not be vented with other
appliances, even if that appliance is of the
condensing type. This includes water heaters
of any efficiency. Common venting can result
in severe corrosion of other appliances or their
venting and can allow combustion gases to
escape through such appliances or vents. Do
not vent the furnace to a fireplace chimney or
building chase.
• This furnace must be vented in compliance with
the current revision of the National Fuel Gas Code
(ANSI-Z223.1/NFPA54). Instructions for determining
the adequacy of combustion air for an installation
can be found in the current revision of the NFGC
(ANSI Z223.1 / NFPA54). Consult local codes for
special requirements. These requirements are for US
installations as found in the NFGC.
• The requirements in Canada (B149.1) are structured
differently. In Canada, venting shall conform to the
requirements of the current (CAN/CGA B149.1 or .2)
installation codes. Consult local codes for special
requirements.
Category IV Appliances
This furnace is classified as a Category IV appliance,
which requires special venting materials and installation
procedures.
Category IV appliances operate with positive
vent pressure and requires thoroughly sealed vent
systems. They also produce liquid condensate, which is
slightly acidic and can cause severe corrosion of ordinary
venting materials. Furnace operation can be adversely
affected by restrictive vent and combustion air piping.