Lifebreath 200ERVD - Manual (Page 23)

23
Outside Weatherhoods
The weatherhoods must have built-in “bird” screen with 1/4 in
(63.5 mm) minimum mesh to prevent birds and rodents from
entering into the ductwork. Do not use smaller mesh as it will
be very susceptible to plugging up. Gravity dampers at the
vents must not be used as they will restrict air flow and often
“seize up”. The preferred location of the outside weather-
hoods is:
• no less than 10 ft. (3 m) apart from each other
• at least 18 in ( 46 cm) above or ground level
• away from sources of contaminants, such as
automobile exhaust fumes, gas meters, garbage
cans, containers, etc.
• not exposed to prevailing winds, whenever reason-
able possible
The outside perimeter of the weatherhood must be caulked
to prevent leakage into the building.
The design and size of the weatherhoods or louvres chosen
by the installer must allow for adequate free area. Water and
debris penetration of the system is minimized when the air-
flow does not exceed 1000 FPM (5.08 m/s) free area velocity.
Ducting from the Weatherhoods
Galvanized sheet metal ducting with sufficient cross section
with an integral single piece vapour barrier should be used to
connect the ERV to the weatherhoods. All ducting must
meet UL Class 1 requirements.
A minimum R value of insulation should be equal to 4
(RSI 0.75)
A good bead of high quality caulking (preferably acoustical
sealant) and taping with a high quality aluminum foil tape is
recommended to seal the duct to both the ERV and the
weatherhood.
Warmside Ducting - General
Ducting from the ERV to the different areas in the building
should be galvanized metal whenever possible.
To minimize airflow losses in the ductwork system, all ducts
should be as short as possible and with as few bends or
elbows as possible. 45° elbows are preferred to 90°
elbows. Use “Wye” (Y) fittings instead of “Tees” (T) when-
ever possible.
All duct joints mist be fastened with screws, rivets or duct
sealant and wrapped with a quality duct tape to prevent leak-
age. We recommend aluminum foil tape.
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 problems
occur. Balancing dampers and/or adjustable grilles are rec-
ommended 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 takeoff con-
nection must be at least a 3 ft (1 m) from a directly con-
nected ERV supply duct if both are connected to the same
duct run. Static pressure of the air handlers return system
should be noted and compensated for if it is apparent that
the static pressure of the return in the air handler will
exceed .1 to .15” W.C.
A damper located just prior to the ERV is required to bal-
ance the stale air exhausted with the fresh air supply enter-
ing 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, vapours and gases. contami-
nants should be controlled at the source so that they are not
dispersed through the building nor allowed to increase to
toxic concentration levels. The energy recovery ventilator
allows for economical operation of the HVAC system while
effectively removing contaminants from the space. In
designing the exhaust portion of the system the exhaust
grilles are placed so as to remove the contaminants while
not allowing them to enter the breathing zone of the occu-
pants.
For contaminants that are 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.