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VII. EXTERIOR MASONRY CHIMNEYS -
CATEGORY I FURNACES ONLY
An exterior masonry chimney is defined as a "Masonry chimney
exposed to the outdoors on one or more sides below the roof
line." The ability to use a clay lined masonry chimney depends
on a parameter not associated with interior chimneys. This variable
is the geographic location of the installation. Researchers have
discovered that the winter design temperatures have a direct
impact on the suitability of this type of venting. In most situations,
the existing masonry chimneys will require a properly sized metallic
liner.
P
O S SIB ILITY O F PR O P ER TY D A M A G E , P ER SO N A L IN J U R Y O R D E AT H
D A M A G IN G C O N D E NS A TIO N C A N O C C U R IN SID E M A S O N RY C H IM N E YS W H EN A
C
S IN G LE FA N A S SIS TED
ATE G O R Y
V E N TED W IT H O U T A D E Q U A T E D ILU TIO N A IR .
FU R N A C E TO A MA S O N R Y C H IM N EY U N LES S TH E F U R N A C E IS C O M M O N V EN T E D
W ITH A D R AFT H O O D EQ U IPP ED A P PL IA NC E O R TH E C H IM N E Y IS LIN E D W ITH A
T
B
M ET A L L IN ER O R
Y PE
M E TA L VE N T .
C H IM N EY S MU S T B E S IZE D IN A C C O R D A N C E W ITH TH E A PP R O PR IATE V EN T IN G
I
TA B LES .
F A N 8 0 % FU R N A C E IS C O M M O N V EN TE D W ITH A D RA FT H O O D
E Q U IP P ED A PP LIA N C E, TH E PO TE N TIA L F O R C O N D E N SA TIO N D A M AG E MA Y
S T ILL E X IS T W ITH EXTR E M ELY C O LD C O N D ITIO N S , LO N G VE N T C O N N E CTO R S ,
E X TER IO R C H IM N E YS , O R A N Y CO M B IN A T IO N O F TH E S E C O N D IT IO N S.
R IS K O F C O N D EN S A TIO N D AM A G E IS BE ST A V O ID E D B Y U S IN G THE M A S O N R Y
C H IM N EY A S A P A TH W A Y FO R PR O P ER LY S IZED M ETA L L IN E R O R
M ET A L V E N T.
Crown
Clay Tile Size Generally
12" x 12" (24" Length)
Throat
Damper
Breech
Clean Out
Figure 8 - Typical Multiple Flue Clay Tile Chimney
C
S
HECKLIST
UMMARY
This checklist serves as a summary of the items to be checked
before venting an 80+ furnace into a masonry chimney. In addition,
we recommend that a qualified serviceman use this checklist to
perform a yearly inspection of the furnace venting system.
This checklist is only a summary. For detailed information on each
of the procedures mentioned, see the paragraph referenced with
each item.
IO-247A
WARNING
I
AFUE
A P P LIA N C E (80 %
FU R NA C E ) IS
D
O N O T C O N N EC T A N 8 0%
A
LL IN S TALL A TIO N S U SIN G M A S O N RY
T
YP E
Wash
Roof Line
Clay Tile Size: 8" x 8" x12"
(Each x 24" Length)
Attic Floor
1/2" to 1" Air Space
Second Floor
First Floor
Water Heater
Vent Connector
F.A.F. Vent
Connector
Natural Draft
Fan Assisted
Water Heater
Forced Air
Furnace
Basement Floor
This inspection is based upon a draft topical report, "Masonry
Chimney Inspection and Relining", issued by the Gas Research
Institute. While not yet finalized, we believe this report represents
the best information on this subject which is currently available.
Proper Chimney
Chimney channel
free of solid and
T
H E
B
Cleanout free of
C
1 - P
HECK
A masonry chimney used as a vent for gas fired equipment must
extend at least three feet above the highest point where it passes
through the roof. It must extend at least two feet higher than any
portion of a building within a horizontal distance of 10 feet. In
addition, the chimney must terminate at least 3 feet above any
forced air inlet located within 10 feet. The chimney must extend at
least five feet above the highest connected equipment draft hood
outlet or flue collar.
If the chimney does not meet these termination requirements, but
all other requirements in the checklist can be met, it may be
possible for a mason to extend the chimney. If this will not be
practical, see Fix 1.
11
Line, terminate with
No
listed vent cap
Termination?
(Check 1)
(Fix 1)
Yes
Change venting
No
liquid fuel
arrangements
appliances?
(Fix 2)
(Check 2)
Yes
Rebuild crown
Crown in good
(Fix 3)
No
condition
and/or Reline
(Check 3)
(Fix 4)
Yes
Reline
debris?
No
(Fix 4)
(Check 4)
Yes
Liner in good
Reline
condition?
No
(Fix 4)
(Check 5)
Yes
Dilution air
Reline
available?
No
(Fix 4)
(Check 6)
Yes
Complete the
installation.
(Check 7)
ROPER CHIMNEY TERMINATION
.
12/04
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