The weatherhoods must have built-in “bird” screen
with 1/4 in (6.35 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
weatherhoods is:
•
no less than 10 ft. (3 m) apart from each other
•
at least 18 in (46 cm) above snow line or ground
level
•
away from sources of contaminants, such
as automobile exhaust fumes, gas meters,
garbage cans, containers, etc.
•
not exposed to prevailing winds
The outside perimeter of the weatherhood must be
caulked to prevent leakage into the building.
The design and size of the weatherhoods or louvers
chosen by the installer must allow for adequate free
area. Water and debris penetration of the system is
minimized when the airflow 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 vapor barrier
should be used to connect the HRV 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 HRV and the weatherhood.
A properly designed ducting system will allow the
HRV to operate at its maximum efficiency. (Air flow
will be restricted by undersized ducting, use of too
many elbows, tees, bends, etc.). Always try to keep
duct runs as short and straight as possible.
NOTE:
Fully insulated ducting with an integral vapor
barrier must be used on all runs passing
through unheated areas in order to avoid
condensation problems and energy losses from
the air steams.
All joints must be airtight, sealed and impervious to
moisture. See specification sheets for each unit for
exact duct sizes and location.
To minimize pressure drop and noise, galvanized
metal ducts, properly sized, are recommended. Keep
ducting as short as possible and use a minimum of
elbows and tees. Connecting sections and shorter
runs may be flexible
ducting one size larger than the metal equivalent.
Use flexible duct connectors at the HRV to
avoid noise transmission.
All duct joints must be secured with screws, rivets or
duct sealant and sealed with aluminum duct tape to
prevent leakage.
The
Ductwork
System
Outside
Weatherhoods
Fully
insulated
ducting
with
an
integral
vapour
barrier
must
be
used
on
all
runs
passing
through unheated
areas in order
to
avoid
condensation
problems
and
energy
losses
from the air
systems.
ATTENTION
19
