ForestAir E-Tech Series - 6.0 DUCTWORK; Ductwork Design and Installation Standards

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© Copyright, Sunrise Tradex Corp., 2018
The air distribution system has the greatest effect on airow. The duct system is totally
controlled by the contractor. For this reason, the contractor should use only industry-recognized
procedures.
Heat pump systems require a specied airow. Each ton of cooling requires between 350 and
450 cubic feet of air per minute (CFM), or 400 CFM nominally.
Duct design and construction should be carefully done. System performance can be lowered
dramatically through bad planning or workmanship.
Air supply diffusers must be selected and located carefully. They must be sized and positioned
to deliver treated air along the perimeter of the space. If they are too small for their intended
airow, they become noisy. If they are not located properly, they cause drafts. Return air grills
must be properly sized to carry air back to the blower. If they are too small, they also can cause
noise.
The installers should balance the air distribution system to ensure proper quiet airow to all
rooms in the home. This ensures a comfortable living space.
An air velocity meter or airow hood can give a reading of system CFM.
6.0 DUCTWORK
Field ductwork must comply with the National Fire Protection Association NFPA 90A, NFPA 90B
and any applicable local ordinances.
Sheet metal ductwork run in unconditioned spaces must be insulated and covered with a vapor
barrier. Fibrous ductwork may be used if constructed and installed in accordance with SMACNA
Construction Standard on Fibrous Glass Ducts. Ductwork must comply with National Fire
Protection Association as tested by U/L Standard 181 for Class I Air Ducts. Check local codes
for requirements on ductwork and insulation.
▪ Duct system must be designed within the range of external static pressure the unit is designed
to operate against. It is important that the system airow be adequate. Make sure the supply
and return ductwork, grills, special lters, accessories, etc. are accounted for in the total
resistance. See airow performance tables in this manual.
▪ Design the duct system in accordance with “ACCA” Manual “D” Design for Residential Winter
and Summer Air Conditioning and Equipment Selection. Latest editions are available from :
“ACCA” Air Conditioning Contractors of America, 1513 16
th
Street, N.W., Washington, D.C.
20036. If the duct system incorporates exible air duct, be sure pressure drop information
(straight length plus all turns) shown in the “ACCA” Manual “D” is accounted for in the system.
▪ Supply plenum is attached to the 19 mm (¾ in) duct anges supplied with the unit. Attach
anges around the blower outlet.
▪ IMPORTANT : If an elbow is included in the plenum close to the unit, it must not be smaller
than the dimensions of the supply duct ange on the unit.
▪ IMPORTANT : The front ange on the return duct if connected to the blower casing must not
be screwed into the area where the power wiring is located. Drills or sharp screw points can
damage insulation on wires located inside the unit.
▪ Secure the supply and return ductwork to the unit anges using proper fasteners for the type
of duct used, and tape the duct-to-unit joint as required to prevent air leaks.
Installation Manual
WARNING
Do not, under any circumstances, connect the return ductwork to any other heat producing
device such as a replace insert, stove, etc. Unauthorized use of such devices may result in
re, carbon monoxide poisoning, explosion, personal injury or property damage.