38
Airflow Balancing
It is necessary to have balanced airflow in ERV/HRV units.
The volume of air brought in from the outside must equal
the volume of air exhausted by the unit if the airflow is not
properly balanced, then:
1.
The ERV/HRV unit may not operate at its maximum
efficiency.
2.
A negative or positive air pressure may occur in the
house.
3.
The ERV/HRV unit may not defrost properly.
4.
Failure to balance ERV/HRV units properly may void
warranty.
Excessive negative pressure may have several undesirable
effects. In some geographic locations, soil gases such as
methane and radon may be drawn into the home though
basement/ground contact areas. In humid geographic
areas, it may also cause condensation to form on inside
walls. Read the application warning in the “Requirements”
on page 11 of this instruction.
BALANCING PREPARATION
1.
All sealing of the duct system has been completed.
2.
All of the ERV/HRV system components are in place
and functioning properly.
3.
Balancing dampers are fully open.
4.
Unit is on HIGH speed.
5.
Airflow 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 airflow.
6.
Operate air handling unit to fan speed for normal
operation.
Balancing the Unit
Balance the unit by measuring the unit’s incoming fresh and
exhausting stale airflows and dampering down the higher
airflow to match the lower airflow.
Airflow Measuring Gauge
Airflow measurement is achieved by using a gauge with an
airflow measuring attachment connected to the high pres
-
sure and the low-pressure side of the gauge. Use a Digital
Manometer (reading down to 0 with resolution of 0.001” w.g.
(0.02 Pa) or a magnehelic gauge for airflow measurement.
NOTE:
A Magnehelic Gauge with a scale of 0 to 0.25” w.g.
(0 to 62 Pa) is necessary for using with a Pitot Tube
and Magnehelic Gauge with a scale of 0 to 1.00”
w.g. (0 to 249 Pa) is necessary for using on Door
Port Balancing).
Gauge Attachments
Common gauge attachments for measuring ERV/HRV air-
flows are:
• The
Pitot Tube
- This will measure the airflow in the
ductwork for any ERV/HRV.
•
Door Port Gauge Tube Set
- This will measure the air-
flow using the door ports for models HRV3-150-TPD,
HRV5-150, HRV5-200-TPD, HRV5-270-TPD-ECM and
ERV5-150-TPD and ERV5-175-TPD.
• Flow Stations - These are installed into the duck work.
Pitot Tube Recommendation
Use a field-provided pitot tube comparable to the Dwyer
®
Series 160 Stainless Steel Pitot Tubes.
Pitot Tube Balancing Procedure
1.
Operate all mechanical systems that have influence on
the ventilation system at high speed. These systems
include the ERV/HRV unit itself and the air handler/
furnace (if applicable). This will provide the maximum
pressure that the system will need to overcome, and
allow for an accurate system balance.
2.
Refer to next page for illustrations of Airflow Balancing
Using the Pitot Tube.
Determining the Actual Airflow
Actual airflow can be determined from the gauge reading.
The value read on the gauge is called the velocity pres-
sure. The pitot tube comes with a chart that will give the
airflow velocity based on the velocity pressure indicated by
the gauge. This velocity will be either feet per minute or
liters per second. To determine the actual airflow, multiply
the velocity by the cross−sectional area of the duct being
measured. This is an example for determining the airflow in
a six inch (152 mm) duct with a Pitot tube reading of 0.025”
w.g. (6.2 Pa) water.
From the chart, this equates to 640 feet (16 meters) per
minute. The 6 inch (152 mm) duct cross−sectional area is
0.2 sq. ft. (0.019 m
2
) The airflow is 640 cfm x 0.2 sq. ft. =
128 cfm (302 L/s x 0.019 m
2
= 60 L/s)
The cross sectional area of some common round duct is:
•
5” (127 mm) diameter duct has 0.14 sq. ft. (0.013 m
2
)
cross−section area
•
6” (152 mm) diameter duct has 0.20 sq. ft. (0.019 m
2
)
cross−section area
•
7” (178 mm) diameter duct has 0.27 sq. ft. (0.025 m
2
)
cross−section area
The accuracy of the airflow reading will be affected by how
close to any elbows or bends the readings are taken. In-
crease accuracy by taking an average of multiple readings
as outlined in the literature supplied with the Pitot tube.
Summary of Contents for ERV5-130
Page 36: ...36 Figure 43 Wiring Diagram HRV5 270 TPD ECM...
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