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NOTE:
Select 1 vent pipe connection
and
1 combustion-air
pipe connection.
AIR
COMBUSTION-AIR _
COMBUSTION-AIR
UPFLOW
COMBUSTION-
AIR
VENT
HORIZONTAL-LEFT
DISCHARGE
NOTE: Select 1 vent pipe connection
and
1 combustion-air
pipe connection.
COMBUSTION-
_
COMBUSTION-
AIR
AIR
AIR
FLOW
DOWNFLOW
COMBUSTION-
AIR
VENT
HORIZONTAL-RIGHT
DISCHARGE
A96187
Fig. 33--Combustion°Air
and Vent Pipe
Connections
NOTE:
Slope combustion-aiI
and _ent pipes a minimum of I4
in. per linear ft with no sags between hangers.
MINOR
PROPERTY
DAMAGE
Failure
to %llow
this
caution
may result
in water
damage
from condensate
dripping.
When
combustion-air
pipe
is installed
above
a suspended
ceiling,
pipe must
be insulated
with
3ig=in. thick Armaflex=
type insulation
Combustion=air
pipe should also be insulated
when
it passes
through
wam_, humid
space
UNIT
MAY
NOT
OPERATE
Failure
to %llow
this caution
may result
in intem_ittent
unit
operation.
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
g with Armaflex=type
insulation
An abandoned masonry chinmey may be used as a raceway %r
properly insulated and supported combustion=air and vent pipes.
Each fltrnace must have its own set of combustion-air
and vent
pipes and be terminated individually, as shown in Fig. 41
Other gas appliances
with their own venting
system
may also use
the abandoned
chimney
as a raceway
providing
it is permitted
by
local code, the cmTent edition
of the National
Fuel Gas (:ode
and
the vent or liner manufi_cmrer's
installation
instructions
Care must
be taken
to prevent
the exhaust
gases
from
one appliance
from
contaminating
the combustion
air of other
gas appliances.
UNIT
CORROSION
HAZARD
Excessive
exposure
to contaminated
combustion
air
may
result
in safety
and perfbrmance
related
problems.
(ombustion
air
must
not
be taken
flom
inside
structure
because
inside
air is frequently
contaminated
by halogens,
which
include
fluorides,
chlorides,
bromides,
and iodides.
These
elements
are fbund
in aerosols,
detergents,
bleaches,
cleaning
solvents,
salts, air ffesheners,
adhesives,
paint,
and
other household
products.
Locate
combustion-air
inlet as far
as possible
from swimming
pool
and swimming
pool pump
house,
FIRE
AND
EXPLOSION
HAZARD
Failure
to %llow
this warning
coutd
result
in fire, property
damage,
persona!
i11jury, or death.
Soh'ent
cements
are
combustible
Keep
away
from
heat,
sparks,
and open
flame
Use only
in well-ventilated
areas.
Avoid
breathing
in vapor
or allowing
contact
with
skin or
eyes
CARBON
MONOXIDE
POISONING
HAZARD
Failure
to
%llow
this
warning
could
result
in
property
damage,
personal
injury,
or death.
Ail
combustion-air
and
vent
pipes
must
be
airtight
and
watertight.
Pipes must also terminate
exactly
as shown in Fig.
36, 37, 38, 39, or 40.
NOTE:
The nlininmm
combustion=air
and vent pipe length (each)
for d-lose furnaces
is 5 ft. Short pipe lengths
(5=g ft) may discharge
water
droplets
These
&oplets
may be undesirable,
and a 12-in.
minimum
off:set pipe section
is recommended,
as shown in Fig. 34,
to reduce
excessive
droplets
from
exiting
vent pipe outlet.
Combustion-Air
and Vent Pipe Diameter
Determine
combustion-air
and vent pipe diameter.
1. Using
Table
7,
individoally
detem_ine
the
smallest
combustion=air
and vent
pipe
diameters
permitted
for each
pipe. 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
tockout
may occur.
NOTE:
Do not count
elbows
or pipe sections
in terminations
or
within
f'umace.
See shaded
areas
in Fig. 36, 37, 38, 39, and 40.
25
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