Bryant 922SA Installation, Start-Up, Operating And Service And Maintenance Instructions Download Page 44

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The concentric vent kit currently cannot be modified to attach an
elbow to the vent portion of the rain cap. A tee attached to the rain

cap could potentially direct the flue gas plume toward the intake air
stream and contaminate the incoming combustion air for the

furnace.
Refer to Fig. 55 for terminations approved for use in Alberta and
Saskatchewan.

Size the Vent and Combustion Air Pipes

General

Furnace combustion air and vent pipe connections are sized for

2-in. (50 mm ND) PVC/ABS DWV pipe. The combustion air and
vent pipe connections also accommodate 60 mm polypropylene

venting systems with outside diameters of approximately 60 mm
(2--3/8 inches). Any pipe diameter change should be made outside

furnace casing in vertical pipe. Any change in diameter to the pipe

must be made as close to the furnace as reasonably possible. See
Fig. 43.
The Maximum Vent Length for the vent and combustion air pipe
(when used) is determined from the Maximum Equivalent Vent

Length in Table 16 minus the number of fittings multiplied by the

deduction for each type of fitting used from Table 17.

OPTIONAL CONFIGURATION FOR COMBUSTION

AIR INLET PIPE

In applications where there is a risk of excessive moisture

entering the combustion air inlet pipe, a moisture trap may be

added to the inlet pipe to help prevent moisture from entering

the furnace from the combustion air inlet pipe. See Fig. 58.
When sizing venting systems, the equivalent length of the

optional moisture trap (15 feet/5 M) must be taken into

account.

NOTICE

Recommended Combustion Air Inlet Moisture Trap

Recommended to prevent moisture from trickling into the furnace

vestibule, a trap can be installed in the intake air pipe near the
furnace. To prevent moisture, connecting a drain line to the trap is

recommended as trace amounts of moisture will evaporate into the
intake air stream. If the combustion air inlet is located near a

moisture exhaust duct, or there are other concerns of excessive

moisture being drawn into the combustion air inlet, it is
encouraged to connect a drain line to the trap.
The trap can be constructed from a running tee of the same
diameter of the intake air pipe with

EITHER

a removable cap

attached to a 6-inch long pipe connected to the tee or the External
Vent Trap Kit to help prevent contaminants from entering the

furnace. See Fig. 58.
The External Vent Trap Kit accessory may be used as a trap for the
combustion air inlet pipe if a large amount of moisture must be

removed. The drain line may be connected to the same drain as the
furnace condensate and the evaporator coil condensate line

ONLY

if the inlet air trap drain and the evaporator coil drain empty into an

open segment of pipe above the drain. See Fig. 14. When using
the External Vent Trap Kit, refer to those instructions for proper

drain connections.
The tee may also be connected to the intake air pipe on the side of

the casing. See Fig. 58.
In any configuration, it will be necessary to add the equivalent
length of the tee (15 feet/5 M) to the Total Equivalent Vent Length

of the venting system.

ADDITIONAL INFORMATION FOR

POLYPROPYLENE VENTING SYSTEMS

Polypropylene venting systems include flexible vent pipe.

These flexible vent pipes have a different equivalent vent

length than straight sections of PVC/ABS DWV vent pipe. Be

sure to make the appropriate deductions from the Maximum

Equivalent Vent Length (MEVL), or additions to the Total

Equivalent Vent Length (TEVL), when applying flexible vent

pipes

polypropylene

venting

systems.

See

the

polypropylene vent system manufacturer’s installation

instructions for details.
When using metric-sized venting systems, use these

equivalencies for obtaining the proper MEVL from the Tables:

Use 2” Vent Tables for 60 mm (o.d.) vent systems

Use 3” Vent Tables for 80 mm (o.d.) vent systems

Use 4” Vent Tables for 100 mm (o.d.) vent systems

NOTICE

The measured length of pipe used in a single or 2--pipe termination

is included in the total vent length. Include deductions from the
Maximum Equivalent Vent Length (MEVL) contained in the

Venting Tables for elbows and flexible vent pipe.

Factory

accessory concentric vent terminations or pipe lengths and elbows

used for “standard” vent terminations do not require a deduction
from the Maximum Equivalent Vent Length. See vent termination

figures associated with Table 16. Include a deduction for a Tee

when used for Alberta and Saskatchewan terminations.

NOTE

: Polypropylene venting systems MAY require additional

deductions from the MEVL, or additions to the TEVL, for vent
terminations and flexible pipe sections. See the polypropylene
venting system manufacturer’s instructions for details on
equivalent lengths of vent terminations and flexible vent pipes,
and for calculating total vent lengths.
To calculate the Total Equivalent Vent Length (TEVL) of the

venting system:

1. Measure the individual distance from the furnace to the ter-

mination for each pipe.

2. Count the number of elbows for each pipe.
3. For each pipe, multiply the number of elbows by the equiv-

alent length for the type of elbow used. Record the equiva-
lent length of all the elbows for each pipe.

4. If a Tee is used on the termination (Alberta and

Saskatchewan, when required) record the equivalent length
of the Tee used.

5. Calculate Total Equivalent Vent Length by adding the

equivalent lengths of the fittings to the lengths of the indi-
vidual vent and combustion air pipes.

6. When using polypropylene venting systems with flexible

vent pipes, perform adjustments for the equivalent length of

the flexible vent pipe to the calculated total equivalent
venting system length. See the polypropylene vent system