Chimney Venting Sizing Handbook

SECTION 14
RELINING MASONRY
CHIMNEYS
14-1 OPTIONS FOR RELINING
When an existing masonry chimney is inspected and found to
require modification in order to make it suitable for use with
gas burning appliances, a variety of options are available.
Where Type B gas vent can be installed within a flue which is
otherwise unused, it may provide the most cost effective
solution to the situation, and is advantageous since it provides
extra insulating value as compared to single wall liners,
thereby reducing condensation. In other situations, a flexible
chimney liner may be easier to install and provide acceptable
service.
14-2 SIZING GUIDELINES
When Type B gas vent is installed within a masonry chimney,
the tables and guidelines covered in previous sections of this
handbook apply.
When a corrugated metallic chimney lining system is to be
installed, current sizing guidelines suggest that Tables I
through IV (as appropriate) may be employed if a reduction
of 20% is applied to all maximum capacity values. Minimum
capacities remain unchanged. Bends or offsets in the
corrugated lining system may require additional capacity
reductions as noted in the previous sections. The 20%
reduction for corrugated metallic chimney liner includes an
allowance for one long radius 90 degree turn at the bottom of
the liner.
REFERENCE
New Vent Sizing Tables, American Gas Association, Catalog
No. T20002, October 1990 or later
National Fuel Gas Code, ANSI Z223.1, or NFPA 54,1958 or
later, American Gas Association
Chimneys, Fireplaces, and Solid Fuel-Burning Appliances,
NFPA211, 1988 or later, National Fire Protection Association
ASHRAE Handbook, Equipment Volume, Chapter on
Chimneys, 1972 Edition or later, American Society of
Heating, Refrigerating, and Air Conditioning Engineers
An Interactive Personal Computer Program for Design and
Analysis of Venting Systems for One or Two Gas Appliances,
Users Manual for Vent 11 (Version 4.1) with Diskettes, Topical
Report (Sept. 1 1989-July 1990), Gas Research Institute
R.L. Stone: A Practical General Chimney Design Method,
ASHRAE Transactions 1971, Paper No. 2175.
48
WARNING
Failure to follow the installation instructions could cause
FIRE, CARBON MONOXIDE POISONING, OR DEATH. If you
are unsure of installation requirements, call the phone
number listed on the instructions or Sizing Handbook.