Lifebreath 500ERV - Manual (Page 15)

15
Fresh Air Supply System
The fresh air supply ductwork from the HRV/ERV may
be directly connected to the return air duct of the
forced air system. Check the air flow balance of the
HRV/ERV with the air handler blower both “ON” and
“OFF” to determine that it does not imbalance the
HRV/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 HRV/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 HRV/ERV, the designer and
installer should be aware of local codes that may
require smoke detectors and/or firestats in the HVAC
or HRV/ERV ductwork.
Because an HRV/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 use of balancing dampers or adjustable grilles to
balance the flow rates into various rooms is
recommended.
The use of balancing dampers or adjustable grilles
as supply air diffusers and air exhaust covers are
recommended. TECHGRILLES™ are round, efficient,
sound absorbing devices available in 4”, 5”, 6” and 8”
(100, 125, 150, and 200 mm) models.
The Integrated HVAC System
Figure A and B
The HRV/ERV has become an integral component of
the HVAC system. Figure A shows an HRV/ERV unit
providing fresh air directly to the return air plenum of a
rooftop heat/cool unit.
In the balanced airflow system, the HRV/ERV exhaust
removes stale room air (eg. from lunch room, storage
or copy area) and returns to the space an equal
amount of fresh outdoor air, making the use of an
economizer obsolete in conjunction with an HRV/ERV.
Many buildings have ceiling return air plenum as
in Figure B. Fresh air from the HRV/ERV can be
introduced directly into the ceiling space but this
should occur near the air handler’s intake.
By operating the HRV/ERV on a 24 hour/7 day battery
backed timer, the unit can be set to operate only when
occupancy or indoor conditions require the air
exchange.
In installations where it is satisfactory to provide
general exhaust from the space, the air to be
exhausted may be taken directly from the return air
plenum to the HRV/ERV as it is drawn back to the air
handler. Fresh air supplied by the HRV/ERV is then
introduced directly into the return air plenum but at a
location closer to the air handler. The air handler
would have a constant running blower to effectively
distribute the fresh air and remove the stale air.
Balancing dampers would be located in both the
HRV/ERV supply and exhaust ducts between the
return air plenum and the HRV/ERV.
NOTE: At no time should the air handler T.E.S.P. on
the return duct exceed that of the HRV/ERV .
AIR FLOW
SUPPLY
AIR FLOW
EXHAUST TECHGRILLE
(optional)
schematic