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Sizing combustion air and vent pipe – Bryant 4-WAY MULTIPOISE 359AAV User Manual

Page 13

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13

Applicable ASTM Standards for Vent Materials

Materials

Sch. 40

Pipe

SDR

Pipe

Cell

Core

Pipe

Fittings

Primer

Solvent

Cement

ABS

D1527

__

F628

D2468

&

D2661

--- ---

D2235

PVC

D1785

D2241

F891

D2466

&

D2665

F656

D2564

CPVC

F441

F442

--- ---

F438

--- ---

F493

ABS to

PVC

--- ---

--- ---

--- ---

--- ---

--- ---

D3138

NOTE:

1. In Canada, all pipe, fittings & cements must conform to

applicable CSA standards or to local codes having juris-

diction.

2. Only use solvent cements that are marked for use with the

specific venting material.

3. ABS to PVC transition joints REQUIRE a special solvent

cement that meets the requirements of ASTM D3138.

4. Refer to ASTM D2855 for general procedure to use for

cementing plastic pipe and fittings.

NOTE: In order to create a seal that allows future removal of
pipe, RTV sealant MUST be used on the inlet pipe where it
joins to the furnace.
NOTE: All vent piping MUST be installed in compliance with
local codes or ordinances, these instructions, good trade practices,
and codes of country having jurisdiction.

1. Determine the best routing and termination for the vent

pipe and air inlet pipe by referring to all of the instructions

and guidelines in this Section.

2. Determine the size required for the vent pipe and air inlet

pipe.

3. Loosely assemble all venting parts without adhesive (pipe

joint cement) for correct fit before final assembly.

4. Furnace shall be installed so as to prevent the accumula-

tion of condensate.

5. Use of vertical piping is preferred because there will be

some moisture in the flue gases that may condense as it

leaves the vent pipe (See Instructions For Horizontal
Vents
).

6. The vertical vent pipe MUST be supported so that no

weight is allowed to rest on the combustion blower.

7. Exhaust vent piping or air inlet piping diameter MUST

NOT be reduced.

8. All exhaust vent piping from the furnace to termination

MUST slope upwards. A minimum of

1

/

4

″ (6 mm) per foot

of run is required to properly return condensate to the fur-

nace drain system.

9. Use DWV type long radius elbows whenever possible, as

they provide for the minimum slope on horizontal runs and

they provide less resistance in the vent system. If DWV

elbows cannot be used, use two, 45° elbows when pos-

sible. On horizontal runs the elbows can be slightly mis-

aligned to provide the correct slope.

10. All horizontal pipe runs MUST be supported at least every

five feet with galvanized strap or other rust resistant ma-

terial. NO sags or dips are permitted.

11. All vertical pipe runs MUST be supported every six feet

where accessible.

12. The minimum pipe run length is 2′ (.6 M).
13. The piping can be run in the same chase or adjacent to

supply or vent pipe for water supply or waste plumbing. It

can also be run in the same chase with a vent from another

90+ furnace.

NOTE: In NO case can the piping be run in a chase where
temperatures can exceed 140° F (60° C). or where radiated heat

from adjacent surfaces would exceed 140° F (60° C).

14. The vent outlet MUST be installed to terminate in the

same atmospheric pressure zone as the combustion air in-

let.

15. The vent system can be installed in an existing unused

chimney provided that:

S

Both the exhaust vent and air intake run the length of the
chimney.

S

No other gas fired appliance or fireplace (solid fuel) is vented
into the chimney.

S

The top of the chimney MUST be sealed flush or crowned up
to seal against rain or melting snow so ONLY the piping
protrudes.

S

The termination clearances shown in Fig. 7 and 8 are
maintained.

16. Furnace applications with vertical vents requiring vent dia-

meter increaser fittings must have increaser fittings in-

stalled in vertical portion of the vent. Condensate will be

trapped in the vent if the vent diameter is increased prior

to having an elbow turned upward. This could cause nuis-

ance tripping of the pressure switch.

Combustion Air and Vent Piping Insulation

Guidelines

NOTE: Use closed cell, neoprene insulation or equivalent. If
Fiberglass or equivalent insulation is used it must have a vapor
barrier. Use R values of 7 up to 10′, (2.1 -- 3.0 M) R--11 if

exposure exceeds 10′. If Fiberglass insulation is used, exterior to

the structure, the pipe MUST be boxed in and sealed against
moisture.

1. When the vent or combustion air pipe height above the

roof exceeds 30″(762 mm), or if an exterior vertical riser is

used on a horizontal vent to get above snow levels, the ex-

terior portion MUST be insulated.

2. When combustion air inlet piping is installed above a sus-

pended ceiling, the pipe MUST be insulated with moisture

resistant insulation such as Armaflex or other equivalent

type of insulation.

3. Insulate combustion air inlet piping when run in warm, hu-

mid spaces.

Sizing Combustion Air and Vent Pipe

Consult Table 3 to select the proper diameter exhaust and

combustion air piping. Exhaust and combustion air piping is sized

for each furnace BTUH size based on total lineal vent length (on

inlet or outlet side), and number of 90° elbows required. Two 45°

elbows can be substituted for one 90° elbow. The elbow or

elbows used for vent termination outside the structure ARE

counted, including elbows needed to bring termination above

expected snow levels. The elbow inside the furnace on the

359AAV IS NOT included in the count.

359AA

V