User Guide

9
Stale Air Return System
The stale air return system is used to draw air from the
points in the building where the worst air quality prob-
lems 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 differ-
ent areas of the building.
Alternately, the stale air may be drawn directly from the
return air duct. When this system is used, the air han-
dler’s blower must constantly operate. The exhaust take-
off connection must be at least 3 ft (1 m) from a directly
connected HRV supply duct if both are connected to the
same duct run. Note and compensate for the static pres-
sure of the air handlers return system if the static pres-
sure of the return in the air handler exceeds .1 to .15”
W.C.
A damper located just prior to the HRV 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 oppo-
site 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. Con-
taminants 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 HVAC system while effective-
ly 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 locat-
ed high on the wall. If contaminants are heavier than air,
a lower placement of the grilles will be required. Infor-
mation on a contaminants specific gravity and toxicity
should be available from chemical data sheets.
Fresh Air Supply System
The fresh air supply ductwork from the HRV may be di-
rectly connected to the return air duct of the forced air
system. Check the air flow balance of the HRV with the
air handler blower both “ON” and “OFF” to determine
that it does not imbalance the HRV more than 10%. Al-
so, 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 HRV acoustically isolated and sepa-
rately 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 HRV, the designer and installer should
be aware of local codes that may require smoke detec-
tors and/or firestats in the HVAC or HRV ductwork.
Because an HRV 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.
Adjustable Grilles
The use of balancing dampers or adjustable grilles as
supply air diffusers and air exhaust covers are recom-
mended. TECHGRILLES™ 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
AIR FLOW
SUPPLY
AIR FLOW
EXHAUST