Bryant 340MAV instruction manual Combustion-Air and Vent Pipe Diameter, Example

A96187

Fig. 27ÐCombustion-Air and Vent Pipe Connections

CAUTION: When combustion-air pipe is installed above a suspended ceiling, pipe must be insulated with 3/8-in. thick Armaflex-type insulation. Combustion-air pipe should also be insulated when it passes through warm, humid space.

CAUTION: When vent pipe is exposed to temperatures below freezing, such as when it passes through an unheated space or when a chimney is used as a raceway, pipe must be insulated as shown in Table 7 with Armaflex-type insulation.

CAUTION: Combustion air must not be taken from inside structure because inside air is frequently contami- nated by halogens, which include fluorides, chlorides, bromides, and iodides. These elements are found in aerosols, detergents, bleaches, cleaning solvents, salts, air fresheners, adhesives, paint, and other household prod- ucts. Locate combustion-air inlet as far as possible from swimming pool and swimming pool pump house.

Excessive exposure to contaminated combustion air will result in safety and performance related problems.

WARNING: Solvent cements are combustible. Keep away from heat, sparks, and open flame. Use only in well-ventilated areas. Avoid breathing in vapor or allow- ing contact with skin or eyes. Failure to follow this warning could result in fire, property damage, personal injury, or death.

WARNING: All combustion-air and vent pipes must be airtight and watertight. Pipes must also terminate exactly as shown in Fig. 30, 31, 32, 33, or 34. Failure to follow this warning could result in property damage, personal injury, or death.

NOTE: The minimum combustion-air and vent pipe length (each) for these furnaces is 5 ft. Short pipe lengths (5-8 ft) may discharge water droplets. These droplets may be undesirable, and a 12-in. minimum offset pipe section is recommended, as shown in Fig. 28, to reduce excessive droplets from exiting vent pipe outlet.

B.Combustion-Air and Vent Pipe Diameter

Determine combustion-air and vent pipe diameter.

1.Using Table 6, individually determine the combustion-air and vent pipe diameters. Pick the larger of these 2 pipe diameters and use this diameter for both combustion-air and vent pipes.

2.When installing vent systems of short pipe length, use the smallest allowable pipe diameter. Do not use pipe size greater than required or incomplete combustion, flame disturbance, or flame sense lockout may occur.

NOTE: Do not count elbows or pipe sections in terminations or within furnace. See shaded areas in Fig. 30, 31, 32, 33, and 34.

EXAMPLE:

An 036080 size furnace located in Indianapolis, elevation 650 ft above sea level, could be installed in an application requiring 3 elbows and 32 ft of vent pipe, along with 5 elbows and 34 ft of combustion-air pipe. Table 6 indicates this application would allow a 2-in. diameter vent pipe, but require a 2-1/2 in. diameter combustion air pipe (2-in. pipe is good for 35 ft with 3 elbows, but only 30 ft with 5 elbows). Therefore, 2-1/2 in. diameter pipe must be used for both vent and combustion-air pipes since larger required diameter must always be used for both pipes. If same installation were in Albuquerque, elevation 5250 ft above sea level, installation would require 2-1/2 in. vent pipe and combustion-air pipe. At 5001- to 6000-ft elevation, 2-in. pipe is only good for 17 ft with 5 elbows, and 2-1/2 in. pipe is good for 70 ft with 5 elbows.

C.Combustion-Air and Vent Pipe Attachment

NOTE: All pipe joints must be watertight except attachment of combustion-air pipe to inlet housing connection, since it may be necessary to remove pipe for servicing.

1.Attach combustion-air pipe as follows:

a.Determine location of combustion-air intake pipe con- nection to combustion-air intake housing as shown in Fig. 27 for application.

b.Reposition combustion-air intake housing plug fitting in appropriate unused intake housing connection.

→c. If required, insert perforated disk assembly (factory- supplied in loose parts bag) in intake housing where combustion-air intake pipe will be connected. If half disk set is required, install with shoulder of disk against stop in combustion-air inlet.

d.Install pipe support (factory-supplied in loose parts bag) into selected furnace casing combustion-air pipe hole. Pipe support should be positioned at bottom of casing hole.

e.Insert 2-in. diameter pipe into intake housing.

NOTE: A 2-in. diameter pipe must be used within the furnace casing. Make all pipe diameter transitions outside furnace casing.