FAQs

Frequently Asked Questions – H&C B-Vent
How do I know what size B-vent to use?
Several variables need to be considered to determine the proper size of a venting system. These
include, but are not limited to, air supply, connector type, BTU input of the appliance, lateral
offset and height of the vent system. To assist you in designing a proper system, download our
"Gas Vent, Chimney Sizing & Application Guide". This guide covers single and multiple
appliance venting and proper chimney sizing. It has a complete set of easy-to-use sizing tables,
the same tables used in the National Fuel Gas Code. Included in the guide are common
definitions, examples, tips on what you should and should not do and many illustrations to help
you along the way.
What are the airspace clearances to combustibles and what are the temperature limits?
1" clearance is required per our UL listing for all installations. The temperature limit is approx
550 deg F for use with gas-fired equipment (natural or propane) that do NOT create a positive
pressure in the vent pipe or condense.
What Class or Category of pipe is B-vent?
The Category is actually applied to the appliance. B-vent is ONLY allowed on Category 1
appliances unless the appliance manufacturer has specifically certified a particular B-vent system
to be used alternatively.
Can B-vent terminate horizontally?
No. Per the sizing tables, all orientations must terminate vertically with a UL listed rain cap,
otherwise the appliance may not vent properly. However, sometimes it is permissible to vent a
Category 1 appliance horizontally with B-vent if a certified flue gas exhaust fan (Exhausto,
Tjerlund, Field Controls) is mounted on the exterior wall to pull the flue gases out.
Can you use sheet metal screws in B-vent?
Generally, NO, Hart & Cooley does not want sheet metal screws used in the assembly or
installation of our Type B gas vent. Screws can generate serious noise problems that adversely
affect the perceived performance and value of our product. They are not needed to secure a
connection because the connection is already UL listed as it is designed. However, there are
exceptions that we allow screws and that is for connections of single-wall pipe to the B-vent.
Fold back the outer wall locking tabs that can act like an access "door" to secure the aluminum
inner wall and single wall pipe together using 1/4" stainless screws.
What causes noisy B-vent?
Often, noise in Type B gas vent is caused by the relative movement of parts in the system with
adjacent parts, with part of the structure, or because of additions or changes to the parts and/or
system. If installed according to Hart & Cooley’s installation instructions, the Type B gas vent is
designed to accommodate the expansion and contraction due to heating and cooling which
occurs within the system. Some common causes of noise in a system could be: screws used in the
assembly of the gas vent system; contact with any part of the structure; roof flashing attached to
the vent pipe; any means of support other than the listed Hart & Cooley support assembly. Click
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