Dedicated Air Handler for Multiple Dwellings

Select a fan that:

has an electrically commutated motor (ECM) and/or utilizes (VFD) controllers

is capable of maintaining a minimum operating static pressure of .25 inches of water column or greater

motors 1 horsepower or larger must meet NEMA premium efficiency standards

motors less than 1 HP must be rated by the Home Ventilation Institute to satisfy these requirements

Install intake to pull air from the outdoors, which does not include unconditioned spaces such as attics and crawl spaces that are ventilated with the outdoors

Install intake:

A minimum of 6" from grade;

A minimum of 10' from contaminant sources or exhaust outlets;

Above local snow or flood line;

A minimum of 18" above an asphalt based roof;

Never on a flat roof

Label exterior intake fitting with the words "Ventilation Air Intake"

Install corrosion resistant screen, louver, or grille material over exterior intake with a hole size of no less than 1/4" and no greater than 1/2" in any direction

Install a motorized damper or equivalent between the intake fitting and the return side duct connection

Damper will be open only when the air handler fan is operating

Design one or more supply fans located upstream of all the supply outlets to run continuously, or

install a system of one or more backdraft dampers to isolate each dwelling unit from the common duct when the fan is not running.

Install all electrical wiring according to manufacturer specifications and applicable code

All mechanically-supplied outdoor air must pass through a filter before combining with conditioned air

Filtration must meet a minimum efficiency of MERV 8

Filter or air cleaning systems that intentionally produce ozone are not allowed.

Install filtration in a readily accessible location for service

Filter opening must allow filter to be fully removed and inserted without bending or damaging the filter

Filter access panel must include gasket or comparable sealing mechanism and fit snugly against exposed edge of filter when closed

Filter plenum must be airtight and mechanically fastened to adjoining ductwork

Mount fan using mechanical fasteners per manufacturer's specifications and applicable code (e.g., seismic restraints)

Isolate air handling unit from the building framing unless specifically designed to be directly attached

Attach ductwork to air handler via a flexible connection and that maintains the intended fan opening

Seal all air moving portions of the system using UL 181 products

Provide air flow by sequenced or scheduled operation of the damper or equivalent technology

Control system must operate both the air handler and the motorized damper or be interlocked to prevent damper operation when air handler is not on

Ensure motorized damper, service disconnect switch, fan, filter, and conditioning coils are accessible for maintenance according to NEC and applicable building code

If fire dampers are required in the fresh air supply duct, install them according to applicable building code

Fire dampers must be accessible for inspection and/or testing

Sealing activities must not interfere with the operation of fire dampers, balancing dampers, or backdraft dampers

Adjust fan speed, dampers, and registers until design specifications are met