Pitot Tube Air Flow Balancing

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 house

•The unit may not defrost properly

•Failure to balance the HRV may void warranty

Prior to balancing, ensure that:

1.All sealing of the ductwork system has been completed.

2.All of the HRV's components are in place and functioning properly.

3.Balancing dampers are fully open.

4.Unit is on high speed.

5.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 dampered back to match the lower reading.

6.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.

Choose the straightest section of duct between the HRV and the weatherhoods. This will be used for both the supply and return ducts. 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.

The Pitot tube should be connected to a magnehelic gauge or other manometer capable of reading from 0 to 0.25 in. (0 - 62 Pa) of water, preferably to 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.

For general balancing it is sufficient 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. Determine which duct has the highest airflow (highest reading on the gauge). Then damper that airflow back to match the lower reading from the duct. The flows should now be balanced.

Actual airflow can be determined from the gauge reading. The value read on the gauge is called 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 either feet per minute or metres per second. To determine the actual airflow, the velocity is multiplied by the cross sectional area of the duct being measured.

25

Page 24 Page 26
Page 25
Image 25
Lifebreath 4TONVENTAC, 60DHW(T) Pitot Tube Air Flow Balancing, Prior to balancing, ensure that, Balancing Procedure
Page 24 Page 26

40DHWDF(T), 4TONVENTAC, 60VENTAC, 40VENTAC, 60DHWH(T) specifications

Lifebreath is a leading manufacturer specializing in indoor air quality solutions, with their series of heat recovery ventilators tailored for both residential and commercial applications. Among their advanced systems, the Lifebreath 60DHW(T), 60DHWDF(T), 4TONVENTAC, 40DHW(T), and 40DHWDF(T) provide exceptional ventilation performance alongside energy efficiency.

The Lifebreath 60DHW(T) and 60DHWDF(T) models are designed for larger spaces, featuring an impressive air flow rate of 60 CFM, making them ideal for homes and businesses that require a robust ventilation solution. These units incorporate a state-of-the-art heat exchange core, allowing for the transfer of heat from outgoing stale air to incoming fresh air, thereby minimizing energy loss.

The significant advantage of Lifebreath's 60DHW series lies in its dual-fan operation, which delivers balanced air flow while maintaining a comfortable indoor climate. Both models are equipped with advanced filtration systems, providing effective capture of airborne pollutants and allergens, promoting optimal air quality.

Moving to the Lifebreath 4TONVENTAC, this unit offers a unique combination of ventilation and cooling functionalities, making it suitable for environments with varying weather conditions. With a 4-ton capacity, it is perfect for larger commercial establishments. The 4TONVENTAC employs innovative technology for efficient energy use, incorporating variable speed drives to adapt to changing ventilation demands, ensuring maximum energy conservation and performance.

The Lifebreath 40DHW(T) and 40DHWDF(T) are perfect for smaller residential applications. With an airflow capacity of 40 CFM, these units maintain comfort without over-ventilating. Similar to the 60DHW models, they feature the same exceptional heat exchange technology to promote energy savings. The 40DHW series also includes user-friendly controls and monitoring features, enabling homeowners to adjust settings for optimal performance based on their specific needs.

A common characteristic across all these models is Lifebreath’s commitment to durability and reliability. Made from high-quality materials, they are built to withstand varying environmental conditions while providing long-lasting service. With easy installation and low maintenance requirements, these heat recovery ventilators prove to be a smart investment for users looking to improve their indoor air quality while reducing energy costs.
Top Page Image Contents