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Indirect Duct System
Safety Warning
Some Building Code and Combustion Appliance Installation Codes do not allow location
of return air grills or any opening such as a breather ‘T’ in an enclosed room with spillage
susceptible combustion appliances. If combustion appliances are used, and not yet enclosed in a
room, locate the grill or breathing ‘T’ outside any future wall locations and a minimum distance
of 6 feet from the combustion appliance.
This method of installation permits localized exhaust of indoor air and uses the existing forced air
system to distribute fresh air.
Although independent room balancing of exhaust air can be achieved with the indirect duct
system, the distribution of fresh supply air cannot be balanced.
Where required by local codes, the HRV/ERV supply duct may be directly connected to the
furnace return air duct. The supply duct shall be positioned as shown on the attached drawing. In
this application no opening such as a breather ‘T’ is used.
Also, where permitted by local codes, the HRV/ERV supply duct may be indirectly connected to
the furnace return air duct using a breather ‘T’. In this application, the breather ‘T’ in installed
into the HRV/ERV supply duct before the connection to the return air duct. Leaving a gap in
the ventilation supply duct in place of the breather ‘T’ is acceptable but not recommended. In
this installation, a grill is placed in the furnace return air duct and the HRV/ERV supply duct is
pointed at this grill at a minimum distance of 100mm (4”) but not greater than 300mm (12”).
The free area of the grill shall not be less than the free area of the supply duct. Call backs have
occurred because it was thought that something had been accidentally left out of the installation.
This method of installation requires that the forced air circulation fan be operated when the HRV
is in use. Furnace circulating fan may be interlocked with HRV. Refer to Wiring Diagram.
See fig. III below.
30 Inches
Minimum
FRESH
SUPPLY AIR
BREATHING ‘T’
FRESH
AIR IN
STALE
AIR OUT
STALE
EXHAUST AIR
fig. III
Summary of Contents for Proventor II Series
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