Combustion Air And Vent System; Combustion Air And Vent Safety; Combustion Air/Vent Pipe Sizing - Bosch BGH96M060B3B Installation Instructions Manual

Installation Instructions

8 Combustion Air and Vent System

8.1 Combustion Air and Vent Safety

This Category IV, dual certified (AHRI and ETL) direct vent furnace is designed for
residential applications. It may be installed without modification to the condensate
system in a basement, garage, equipment room, alcove, attic or any other indoor
location where all required clearance to combustibles and other restrictions are
met. The combustion air and the venting system must be installed in accordance
with Section 5.3, Air for Combustion and Ventilation, of the National Fuel Gas Code
Z223.1/NFPA 54 (latest edition), or Sections 7.2, 7.3 or 7.4 of CSA B149.1,
National Gas and Propane Codes (latest edition) or applicable provisions of the
local building code and these instructions.
NOTICE:
The "VENT SYSTEM" must be installed as specified in these
f
instructions for Residential and Non HUD Modular Homes.
The direct vent system is the only configuration that can be
installed in a Non HUD Modular Home.3.
NOTICE:
Do not discharge exhaust gases directly into any chimney
f
or vent stack. If vertical discharge through an existing
unused chimney or stack is required, insert piping inside
chimney until the pipe open end is above top of chimney
and terminate properly. In any exterior portion of chimney,
the exhaust vent must be insulated.
NOTICE:
When combustion air pipe is installed above a suspended
f
ceiling or when it passes through a warm and humid
space, the pipe must be insulated with 1/2" Armaflex or
other heat resistant type insulation if two feet or more of
pipe is exposed. Vent piping must be insulated if it will be
subjected to freezing temperatures such as routing through
unheated areas or through an unused chimney.
NOTICE:
Prior to installing the exhaust vent pipe, ensure that the
f
black plastic cap is removed from the coupler on furnace
cabinet. The cap is only used to prevent debris from
falling into the vent opening and into the inducer during
installation. Refer to Figure 21.
2 6 |
Figure 22 Protective Cap Removal

8.2 Combustion Air/Vent Pipe Sizing

The size of pipe required will be determined by the furnace model, the total length
of pipe required and the number of elbows required. Table 6, "Maximum Equivalent
Pipe Length" lists the maximum equivalent length of pipe allowed for each model of
furnace. The equivalent length of elbows is shown in Table 8, "Equivalent Length of
Fittings".
The equivalent length of the vent system is the total length of straight pipe PLUS the
equivalent length of all of the elbows. The following rules must also be followed:
1. Long radius (sweep) elbows are recommended. Standard elbows may
be used, but since they have a longer equivalent length, they will reduce
the total length of pipe that will be allowed. Short radius (plumbing vent)
elbows are not allowed. The standard dimensions of the acceptable elbows
are shown below.
2. The maximum equivalent length listed in Table 6, "Maximum Equivalent
Pipe Length" is for the vent piping and the air intake piping separately. For
example, if the table allows 60 equivalent feet for a particular model, then
the vent can have 60 equivalent feet of pipe, AND the combustion air intake
can have another 60 equivalent feet of pipe.
3. Three vent terminal elbows (two for the vent and one for the combustion air
intake) are already accounted for and need not be included in the equivalent
length calculation.
4. All combustion air and vent pipes and fittings must conform to American
National Standards Institute (ANSI) and American Society for Testing and
Materials (ASTM) standards, D1785 (Schedule 40 PVC, including IPEX
System 1738 Schedule 40 PVC), F441 (Schedule 40 CPVC), D2665
(PVC-DWV), F891 (PVC-DWV Cellular Core), D2661 (ABS-DWV) or D1527
(Schedule 40 ABS). Pipe cement and primer must conform to ASTM
Standard D2564 (PVC), F493 (CPVC) or D2235 (ABS). If ABS pipe is to
be used, any joint where ABS pipe is joined to PVC pipe must be glued with
cement that is approved for use with BOTH materials. As an alternate, use
all purpose cement, to bond ABS, PVC, or CPVC pipe when using fittings
and pipe made of the same materials. Metallic materials must not be used
for venting or air intake.
5. If a flexible connector is used in the vent system, it must be made of
a material that is resistant to acidic exposure and to at least 225° F
temperature. Flexible connectors are also allowed in the combustion air
pipe.
6. All models are supplied with 2" vent connections. When the pipe must be
increased to 3" diameter, the transition from 2" to 3" must be done as close
to the furnace as possible. For upflow models, the transition from 2" to 3"
should be done immediately above the furnace. For downflow or horizontal
models, the transition from 2" to 3" pipe should be done immediately after
exiting the furnace.
Bosch 96% AFUE Condensing Gas Furnace - BTC 770503101 J (06.2023)
Remove cap