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\'ENTTNG
TROUBLE
Most
venting
problems
are
caused
by
incorrect
vent
sizing, improper
installation,
or
inadequate
air supply. A
preliminary
check
for a
field
problem
might
include:
.
Using a
draft
meter
to
determine
if
venting
system
draft meets
manufacturer's
specifica-
tions.
r
Checking
the vent
sizing according
to
manufacturer's
specifications,
appliance
input,
and venting
configuration.
r
Examining
the
entire
venting system
for
faults
such
as disconnected
joints
or
damaged vent
sections.
o
Making
sure vent
and air openings
are
not
obstructed.
lf these
procedures
do not reveal
the source
of the
problem,
troubleshooting
may
include
attention to
common
venting
problems
discussed below.
FLUE GAS
SPILLAGE
Spillage
occurs when flue
gases
cannot
exit
the
vent system and back up into
the dwelling.
A
primary
symptom of appliances
equipped
with
a
Vent
Safety Shutoff System
(flue
spill
switch)
is
unexplained appliance
shutoffs.
Other
symptoms
of
flue
gas
spillage
at the draft
hood include cendensation on
walls and
windows and/or
noticeable
odours.
But spillage
may
also
result
in the release
of
carbon
monoxide,
a
colourless, odourless,
highly toxic
gas.
A simple spillage test can
be
conducted
if spillage
is
suspected; see owners
manual.
CAUSES
OF SPILLAGE
AND
CORRECTIVE
ACTION
Incorrect
Vent
Sizing
(H)
lf
the
vent
is too
small
or
too short,
spillage
may
occur.
lf the
vent
is too
large,
excessive
dilution
air may
cool flue
gases
and
reduce
draft,
causing
spillage. The
vent
cap size
should
also
be
checked. Check manufacturer's
instruc-
tions,
appliance input rating,
and
appropriate
sizing
tables.
Venting
Condltion
Loose
joints
can
affect
draft
and
cause
spillage.
Mashed-in
vent
sections
and damaged
vent
caps can
restrict
flow and
cause
spillage.
Examine and
replace
as
needed.
Obsfructions
Small animals
or
birds
may
get
into and
block
the vent
or
draft
hood
outlet.
Dust, lint,
and
foreign objects
may
obstruct
air
inlets. Remove
obstructions
and
clean oPenings.
Lateral
Run
(L)
Lengthy
horizontal
or
non-vertical
runs
cause
resistance
to flow
and
may
reduce
draft enough
to cause
spillage.
The
pitch
of
lateral runs
can
also
be a
problem; lateral
runs should
be
pitched
114" rise
per
foot
of
horizontal
run
from
the
appliance
to
the
vent.
Elbows
Too many elbows
cause
excessive
restriction
of flow and may
result
in spillage.
Usually, two
90 degree turns
can
be tolerated
in a
properly
sized venting
system.
More
than
two may-
cause
problems
and
necessitate
changing the
-
system.
Negative
pressure
in the
Dwelling
An
extremelly
tight
house
may
not supply
adequate combustion
and
venting
air. Use
of
mechanical exhaust
such
as
a dryer
vent
or
range vent may
worsen
the
problem.
An
air
exchange
system
must
be installed
In
the
dwell'
ing to correct
this
Problem.
Flue Gas Cooling
Venting exposed
to extremelY
cold
temperatures
or
venting
of single
wallconstruc-
tion
lose heat
needed
to
maintain
draft;
massive
masonry
chimneys
absorb
needed
heat. lf the
flue
gases
cool
excessively,
draft
is reduced and
spillage
may
result.
Use
proper
materials,
insulate
and
protect
properly'
reline
when necessary.
Down
Drafts
tn certain
wind
conditions
and
in certain
relationships
with
nearby
structures
and
objects,
high
pressure
conditions
rnay
atfect
draft
negatively.
Relocate
the
vent
cap,
raise
its heighl, or
use
an
approved
high
wind cap.
Pl|OBLEMS
SHOOTING
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