Lifebreath 1500E-ECM, Installation Manual

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Page 15
B
ALANCING THE
A
IRFLOWS
It is necessary to have balanced air flows in an HRV. The volume of air brought in from the outside must equal the
volume of air exhausted by the unit. If the air flows are not properly balanced, then;
•
The HRV may not operate at its maximum efficiency
•
A negative or positive air pressure may occur in the building
• The unit may not defrost properly
• Failure to balance HRV properly may void warranty
Read the Application Warning on the front of this manual!
Prior to balancing, ensure that:
1. All sealing of the ductwork system has been completed.
2. All the HRV's components are in place and functioning properly.
3. Balancing dampers are fully open.
4. Unit is on HIGH speed.
5. Air flows in branch lines to specific areas of the house should be adjusted first prior to balancing the unit. A
smoke pencil used at the grilles is a good indicator of each branch line's relative air flow.
6. After taking readings of both the stale air to the HRV duct and fresh air to the house duct, the duct with the
lower CFM ([L/s] velocity) reading should be left alone, while the duct with the higher reading should be adjusted
back to match the lower reading.
7. Return unit to appropriate fan speed for normal operation
Balancing Procedure
The following is a method of field balancing an HRV using a Pitot tube, advantageous in situations when flow stations are
not installed in the ductwork. Procedure should be performed with the HRV on high speed.
1.
The first step is to operate all mechanical systems on high speed, which have an influence on the ventilation system,
i.e. the HRV itself and the forced air furnace or air handler if applicable. This will provide the maximum pressure that
the HRV will need to overcome and allow for a more accurate balance of the unit.
2. Drill a small hole in the duct (about 3/16"), three feet downstream of any elbows or bends, and one foot upstream of
any elbows or bends. These are recommended distances, but the actual installation may limit the amount of straight
duct.
3. The Pitot tube should be connected to a manometer capable of reading 3 digits of resolution. The tube coming out of
the top of the pitot is connected to the high pressure side of the gauge. The tube coming out of the side of the pitot
is connected to the low pressure or reference side of the gauge. Insert the Pitot tube into the duct; pointing the tip
into the airflow.
4. For general balancing it is enough to move the pitot tube around in the duct and take an average or typical reading.
Repeat this procedure in the other (supply or return) duct.
5. Determine which duct has the highest airflow (highest reading on the manometer).
6. Adjust the higher airflow adjusting the field supplied damper. The flows should now be balanced. Actual airflow can
be determined from the gauge reading. The value read on the gauge is called the velocity pressure. The Pitot tube
comes with a chart that will give the air flow velocity based on the velocity pressure indicated by the gauge. This
velocity will be in either feet per minute or meters per second. To determine the actual airflow, the velocity is
multiplied by the cross sectional area of the duct being measured.
Attention
• Continuous, excessive, positive pressure may drive moist indoor air into the external walls of the building.
Once inside the external walls, moist air may condense (in cold weather) and degrade structural components
or cause locks to freeze.
•
Continuous, excessive, negative pressure may have several undesirable effects. In some geographic locations,
soil gases such as methane and radon gas may be drawn into the home through basement or ground contact
areas and may also cause the backdrafiting of vented combustion equipment.