10/04/2007 6
NI802
Mechanical Installation
Clearances and Accessibility
Zero clearance is allowed on all sides for combustible materials. However, 36” should be allowed at the
front for operation, maintenance, and service.
To reduce the risk of rusting and appearance, do not install the unit directly on the ground or on a floor
that is likely to be wet. In such environments the unit must be elevated by use of a sturdy non-porous
material.
General Ductwork and Airflow Requirement
Design the airflow ductwork to meet the maximum operating airflow (CFM) for the kW
and
cooling ton
requirements (whichever is larger). This document does not provide installation and design information
for the ductwork external to this product. It is assumed this is being accomplished by a professional and
trained installer understanding ductwork design, airflow/static pressure resistance, and forced air
distribution systems. Key requirements information:
-
Heating and cooling blower speed or minimum CFM is setup independently. See the “Blower
Speed Selection” to match the airflow capacity with the ducting design.
-
The airflow distribution system shall be designed for a maximum of 0.5” SP. Ideally the design
should be set at 0.3” to 0.4” SP.
-
The variable speed, ECM™ motor, is sensitive to inlet static pressure. In order for the motor to
arrive at the setup CFM (motor RPM adjust according to static pressure) the inlet must have a
minimum resistance of about 0.15 to 0.2. If you do not have return air ducting and you’re simply
allowing free return air circulation through a filter at this Electric Furnace inlet, you may need to
have a slight restriction in order for the blower motor to arrive at its setup speed.
-
All transitions must have a slope of 30° to 45°. There shall be no 90° bends or surfaces causing
airflow bounce/eddy current.
-
The manufacturer strongly recommends the return air entering the bottom (under the blower) of
the cabinet. For smaller kW and smaller cooling (10 kW or 2-ton) it is permissible to bring the
air in on either side of the 32” cabinet.
-
Previous Specification Chart shows the minimum CFM associated with the kW. Again this is
setup as detailed in the “Setup or Programming” section.
-
The cooling CFM is also selected but is
not
shown on the Specification Chart. In many cases the
airflow distribution system is probably designed to meet the
cooling
requirement.
-
The room registers and individual 5” or 6 “ runs must also match the total setup or planned CFM
for this installation. Typically a 6” round and a typical room register is rated at 100 CFM.
-
All distribution ducts (supply
and
return) must be sized for the setup or planned total CFM
requirement. The attached duct sizing chart shows various distribution duct sizes relating to their
ability to properly handle the stated CFM.
-
Seal connections between this unit and ductwork, all ductwork connections, etc. as required to
reduce or eliminate air leakage. Sealing all connections will also reduce air noise.
Comment
: The ECM™ motor efficiently relates to system static pressure. On one hand a minimum of
about 0.2” SP is required for the motor to adjust itself, but above 0.3” it begins to drain high current. For
information, consider (at 240):
1.0” SP – 3.4A
0.8” SP – 2.5A
0.5” SP – 0.9A
0.2” SP – 0.4A
Continuous Air – 0.25A
