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windows andventilation openings, thenumber of doors to
the outside,internal d oorswhichcan closeoff the
unconfined s paceand the overall a ir tightness o f the
building c onstruction.
Many newbuildings andhomes ( andolder ones thathave
beenweatherized mustbe considered a s beingtight
construction
and, t herefore, infiltration will n otbesufficient to
supply t henecessary airforcombustion andventilation.
Abuilding c anbeconsidered asbeing oftightconstruction
when:
a. Wallsandceilings exposed to the outside havea
continuous water v apour r etarder witha rating of one
permor less,openings h avegaskets or aresealed
and/or;
b. Weather-stripping
has been added on operable
windows and doors, and/or;
c. Caulking or sealant hasbeen applied t oareas such as
jointsaround window anddoorframes, between s ole
plates andfloors, b etween wail-ceiling joints, b etween
wall p anels, atpenetrations
forplumbing, electrical and
fuel l ines andatother o penings.
2.4.2
Duct recommendations
When ducting supplies air to a space other than where
the furnace
is located, the return air must be sealed and
also be directed
to the space other than where
the
furnace
is located.
Incorrect ductwork
termination
and
sealing will create a hazardous
condition that can lead
to bodily harm.
Return air grilles and warm air registers
must not be
obstructed.
IMPORTANT:
The dampers should be adequate to prevent
cooled
air from
entering
the
furnace,
and
if manually
operated,
must be equipped
with the means to prevent
operation of either the cooling unit or the furnace, unless the
damper is in the full cool or heat position.
NOTE:
The back should
not be cut out for return air
ducting.
The proper sizing of warm air ducts is necessary to ensure
satisfactory
furnace
operation.
Ductwork
should
be
in
accordance
with
the
latest
editions
of
NFPA-90A
(Installation
of Air Conditioning
and Ventilating
Systems)
and NFPA-90B
(Warm
Air Heating
and Air Conditioning
Systems) or Canadian equivalent.
Also, there is provision on this furnace for a bottom return air
duct. Knockouts are provided in the floor of the furnace to
facilitate
the cut-out requirement
for the air filter rack and
return ductwork. (We recommend
the use of this opening for
horizontal and counterflow installations).
The following
recommendations
should
be followed
when
installing ductwork:
a.
Install locking type
dampers
in all branches
of the
individual
ducts
to facilitate
balancing
the
system.
Dampers should be adjusted such a way as to ensure
the proper static pressure at the outlet of the furnace;
b.
A flexible duct connector
of non-combustible
material
should be installed at the unit on both the supply and
return air side. In applications
where an extremely quiet
operation is necessary, the first 3 m (10') of supply and
return ducts should be internally
lined with acoustical
material (if possible);
c.
In cases where the return air grille is located close to
the fan inlet, there should
be at least one 90 ° turn
between fan inlet and grille. Further reduction in sound
level
can
be accomplished
by
installing
acoustical
turning vanes or lining the duct as described in item b.
above;
d.
When a single air grille is used, the duct between grille
and furnace must be the same size as the return air
opening in the furnace.
When installing the furnace with cooling equipment for year
round operation,
the following
recommendations
must be
followed for tandem or parallel air flow:
POISONOUS
CARBON MONOXIDE GAS HAZARD
Install the evaporator
coil on the supply side of the
furnace ducting ONLY.
An evaporator
coil installed on the return air side of the
ducting can cause condensation
to form inside the heat
exchanger,
resulting in heat exchanger
failure.
This in
turn can result in death, bodily injury.
a.
On tandem
airflow applications,
the coil is mounted
after the furnace
in an enclosure
in the supply
air
stream. The furnace blower is used for both heating and
cooling airflow;
b.
On
parallel
airflow
installation,
dampers
must
be
provided to direct air over the furnace heat exchanger
when heat is desired and over the cooling coil when
cooling is desired.
2.4.3
Venting instructions
(chimney installation)
The furnace must be vented to the outside,
in accordance
with local codes and other authorities having jurisdiction.
The supply ductwork
should
be attached
to the flanged
opening provided at the discharge end of the furnace. See
Figures 10 and 11, for the dimensions
of this opening.
Oil fired
appliances
must be connected to flues having
sufficient
draft at all times to ensure safe and proper
combustion.
Knockouts
are provided on both sides of the furnace to cut
the required size of opening for the installation of the return
air ductwork. This can be done on either the right or the left
side
of
the
furnace.
See
Table
2
for
location
and
dimensions.
For
additional
venting
information
please
refer
to
ANSI/NFPA
211 Chimneys,
Fireplaces,
Vents
and Solid
Fuel Burning Appliances
and/or the CSA B139 Installation
Code.
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