Dettson CC15-M-V, Installation Instructions And Homeowner'S Manual

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Figure 14 – Horizontal installation detailed
5 DUCT INSTALLATION
5.1 GENERAL REQUIREMENTS
The duct system should be designed and sized according
to accepted national standards such as those published
by: Air Conditioning Contractors Association (ACCA),
Sheet Metal and Air Conditioning Contractors National
Association (SMACNA) or American Society of Heating,
Refrigerating and Air Conditioning Engineers (ASHRAE).
Consult The Air Systems Design Guidelines reference
tables available at your local distributor.
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. See NFPA 90B
or local code for further requirements.
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.
5.2 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
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)
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