The fresh air supply ductwork from the ERV may be
directly connected to the return air duct of the forced air
system. Check the air flow balance of the ERV with the air
handler blower both “ON” and “OFF” to determine that it
does not imbalance the ERV more than 10%. Also, it is
advisable to include a short length of flex duct or other non-
metallic connector in this hard ducted line in order to keep
the ERV acoustically isolated and separately grounded
(electrically) from the air handler. This will avoid a possible
shock hazard to service people if a short to ground develops
in one of the devices.
It may be necessary to install a separate fresh air supply
ductwork system if the heating is other than forced air.
When installing an ERV, the designer and installer should
be aware of local codes that may require smoke detectors
and/or firestats in the VAC or ERV ductwork.
Because an ERV is designed to bring fresh air into the
building, structures may require supply voltage interrupt
when smoke or flame sensors are triggered, or when a
central fire alarm system is activated.
Supply air grilles may be ceiling or high wall mounted.
Avoid locating incoming fresh air grilles that could cause a
direct draft on the occupants as the incoming air may be
below room temperature. A reheat duct heater can be
installed to improve occupant comfort.
The stale air return system is used to draw air from the
points in the building where the worst air quality problems
occur. Balancing dampers and/or adjustable grilles are
recommended on all return air lines which are used during
installation to help balance the “draw” from different areas
of the building.
Alternately, the stale air may be drawn directly from the
return air duct. When this system is used, the air handler’s
blower must constantly operate. The exhaust take-off
connection must be at least 3 ft (1 m) from a directly
connected ERV supply duct if both are connected to the
same duct run. Note and compensate for the static pressure
of the air handlers return system if the static pressure of the
return in the air handler exceeds .1 to .15” W.C.
A damper located just prior to the ERV is required to
balance the stale air exhausted with the fresh air supply
entering the building.
Return air suction points should be located on the opposite
side of the room from the fresh air inlet. The inlets may be
located in the ceiling or high on the walls and fitted with
inlet grilles.
Many commercial activities produce air contaminants in the
form of dusts, fumes, mists, vapors and gases.
Contaminants should be controlled at the source so they are
not dispersed through the building or allowed to increase to
toxic concentration levels. The ventilator allows for
economical operation of the VAC system while
effectively removing contaminants from the space. In
designing the exhaust portion of the system the exhaust
grilles are situated to remove the contaminants while not
allowing them to enter the breathing zone of the occupants.
For contaminants lighter than air, grilles should be located
high on the wall. If contaminants are heavier than air, a
lower placement of the grilles will be required. Information
on a contaminants specific gravity and toxicity should be
available from chemical data sheets.
Stale Air Return System
Fresh Air Supply System
Adjustable Grilles
The use of balancing dampers or adjustable grilles as
supply air diffusers and air exhaust covers are
recommended. TEC GRILLES™ are round, efficient,
sound absorbing devices available in 4”, 5”, 6” and 8”
(100, 125, 150, and 200 mm) models.
Part# 99-EAG4 4” diameter Techgrille
Part# 99-EAG5 5” diameter Techgrille
Part# 99-EAG6 6” diameter Techgrille
Part# 99-EAG8 8” diameter Techgrille
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