Dettson Chinook C15-M-V Instructions D'installation Et Manuel Du Propriétaire page 14

The duct system should be sized to handle the required
system design aiflow at the design external static
pressure. When a furnace is installed so that the supply
ducts carry air circulated by the furnace to areas outside
the space containing the furnace, the return air shall also
be handled by duct(s) sealed to the furnace casing and
terminating outside the space containing the furnace.
This furnace may be installed, with a two pipe sealed
combustion configuration (direct vent), in a space utilized
as part of the return air supply. A filter must be installed
in the return opening of the furnace and a grill should be
installed in the space to allow proper circulation of air.
Secure ductwork with proper fasteners for type of
ductwork used. Seal supply and return duct connections
to the furnace with code approved tape or duct sealer.
Ductwork passing through an unconditioned space
should be insulated to enhance system performance.
When air conditioning is used, a vapour barrier is
recommended.
Maintain a 1 in. (25 mm) clearance from combustible
materials to supply air ductwork for a distance of 36 in.
(914 mm) horizontally from the furnace.
Flexible connections can be used between ductwork and
furnace to prevent transmission of vibration.
Many states, provinces and localities are considering
or have implemented standards and/or restrictions on
duct sizing practices, ductwork leakage, and/or ductwork
thermal, airflow and electrical efficiencies. CONSULT
LOCAL CODE OFFICIALS for ductwork design and
performance requirement in your area.
4.2 DUCT EXTERNAL STATIC
PRESSURE
Higher than prescripted static pressure will decrease the
air flow, causing excessive temperature rise, opening of
the thermodisk, failure of the heat exchanger and / or
poor performance of the heat pump / air conditioning.
To measure total external static pressure, proceed as
follow:
1. Run the furnace at the system maximum airflow.
This is usually acheive in cooling with a call on Y2.
If you have a communicating system, unplug your
thermostat, make the appropriate dipswitch setting
using table 21 and jump either Y2 or Y1, depending
on the airflow needed.
2. Return duct : Make sure the furnace filter is clean
and measure the static pressure between the filter
and the inlet of the furnace (negative pressure
reading)
3. Supply duct : Measure the static pressure between
the furnace and the cooling coil (positive static
pressure). Tape up the hole when test is complete.
4. Substract the inlet pressure from the supply
pressure. For exemple, if you measured 0.3"w.c.
in the supply and -0.2" in the return:
0.3"w.c. - (-0.2"w.c.) = 0.5"w.c.
If the total external static pressure exceeds the maximum
listed on the furnace rating plate, check for closed
dampers, register, unproperly size duct work or incorrect
dipswitch settings. Make sure the temperature rise is
coherent with the furnace rating plate.
4.3 SMART DUCT SYSTEM
Dettson Industries also offers the Smart Duct System.
Please refer to the Smart Duct Manual (X40240) for
proper installation of this system.
Please note Smart Duct system can only be used with
approuved Smart Duct furnaces.
4.4 RETURN AIR CONNECTIONS
The return air duct must be connected to the bottom, left
side or right side. If necessary (depending on your filter
restriction), provision should be made for a double return.
In downflow configuration, side return air is not permitted,
it must be connected to the bottom of the furnace.
Connection to the back of the furnace is prohibited.
Static pressure in the return air duct should be -0.2"w.c.
at system maximum airflow.
At least two 90° elbows and 10 ft of straight duct
should be installed before the first return branch to trunk
connections to avoid noise or before return grill.
4.4.1 Bottom return
Cut a rectangular opening on the bottom plate of the
furnace using the knock-outs.
In Upflow orientation when using the bottom inlet, return
air base can be used. This base allows the connection of
the duct on the side with a bottom inlet. See table 24 for
the part number corresponding to your furnace.
4.4.2 Side return
Remove 4 knock-outs on the side of the furnace of the
8 knock-outs available. Use table 3 for suggested return
size. Install the return air inlet as per local codes.
Table 3 – Suggested Return size
Model
C15-M-V/C15-M-S
C30-M-V/C30-M-S
C45-M-V/C45-M-S
C60-M-V/C60-M-S
C75-M-V
C105-M-V
C120-M-V
13
Return size
16" x 24.00" or 16" x 20.00"
16" x 24.00" or 16" x 20.00"
16" x 24.00" or 16" x 20.00"
16" x 24.00"
16" x 24.00"
16" x 24.00"
16" x 24.00"