6
Direct Connection of Supply Airstream and Exhaust Air-
Stream to the Furnace Cold Air Return (Return/Return
Method) — The HRV must be balanced. It is mandatory that
the furnace blower run continuously or HRV operation be in-
terlocked with the furnace blower. Check local codes/authority
having jurisdiction for acceptance. See Fig. 17 and 18.
Direct Connection of Both Supply Airstream and Exhaust
Airstream to the Furnace Cold Air Return and Supply Air
Side (Supply/Return Method) — The HRV must be balanced.
It is recommended that the furnace blower run continuously or
HRV operation be interlocked with the furnace blower. Check
local codes /authority having jurisdiction for acceptance. See
Fig. 19 and 20.
Step 7 — Airflow Balancing —
If the unit airflows
are not properly balanced then the unit may not operate at max-
imum efficiency and energy recovery core damage may occur.
An improperly balanced unit could cause negative or
positive pressure in the home causing cold air to enter or other
combustible equipment to backdraft. Also, the unit may not
defrost properly.
The balancing procedure consists of measuring the exhaust
air leaving the system and the supply air entering the system
and ensuring that these two are equal. A deviation of 10% or
less is acceptable. In such cases, it is recommended to have a
greater amount of exhaust air than supply which will increase
the supply-air temperature.
AIRFLOW STATION METHOD — To measure airflow with
an airflow station, perform the following:
1. Cut the duct and insert the flow measuring station.
Make sure that the flow measuring station air direction
arrow points in the direction of the airflow. Secure the
flow measuring station with duct tape. See Fig. 21.
2. Before taking the reading, make sure that the Magne-
helic gage is level and at 0. See Fig. 22.
3. Start the HRV and other system devices if applicable
(furnace and air handler) and refer to the flow measur-
ing station chart to determine unit airflow velocity.
4. The airflow is regulated by a balancing damper located
inside the collar of the HRV. Adjust the Supply Air Out
damper until the desired velocity is achieved. See Fig. 23.
5. Adjust the Exhaust Air Out damper in the same
manner.
Fig. 17 — Direct Connection to Furnace
(Return/Return)
FORCED AIR
FURNACE
COOL AIR
RETURN
RETURN AIR
1 M
(3'-3") MIN
RECOMMENDED
* UNIT IS NORMALLY BALANCED ON HIGH SPEED
WITH FURNACE BLOWER ON.
OUTDOORS
* DUCTS CONNECTION MAY VARY
DEPENDING ON MODEL
EXHAUST AIR FROM VARIOUS
PARTS OF HOME.
I.E., BATHROOMS (IF REQUIRED)
KITCHENS (IF REQUIRED)
NOTES:
1. Furnace blower may be required to operate when HRV is on to provide good air distribution.
2. Weather hood arrangement is for drawing purposes only. 6
″
(2 m) minimum separation recommended. 18
″
(460 mm) above grade minimum.
3. Due to the differences in pressure between the HRV and the equipment it is being connected to, the HRV’s airflow must be confirmed on site,
using the balancing procedure found in the installation manual.
Fig. 16 — Partially Dedicated System Airflow Diagram
