Air Flow Capture Hood

If you find yourself wondering, "what is a balometer?", a good balometer definition is this: an air flow and volume measuring instrument with a large fabric flow capture hood on top that directs airflow to a specialized anemometer. To be specific, the term balometer was actually coined by TSI in the 1980s to refer to their proprietary line of capture hoods, but now it has become synonymous with air flow hood and other such terms. Most folks now will say either "capture hood" or "balometer" to refer to this testing instrument. There are a lot of ways actually to refer to this meter, and we'll use them all fairly interchangeably in this guide.

These flow capture hood devices are used primarily in the field we call TAB, or "testing, adjusting, and balancing". To put it simply, TAB is the process of testing and fine-tuning a whole building (envelope) air flow system to provide for maximum operational efficiency and ideal comfort levels for the building occupants. To put it even more plainly, TAB is just about making sure everything is working at its best and that the air system feels good for the people in the building.

Having a high-quality balometer air flow capture hood is essential to doing air balancing or TAB work because the nature of the job is highly sensitive to fluctuations. Put another way, because you are dealing with a whole building system, this work is both art and science that requires training and, above all, accurate and reliable testing equipment. Because of temperature changes in the building envelope, readings can change within seconds at registers and ducts, so you need an instrument that can accurately track of this data. Once you have collected all the relevant data (you will need some on the job training and experience to understand this process completely, and you probably aren't even looking for a balometer if you don't know at least some of this), you check the data against the relevant manufacturer specs and efficiency standards set forth by the customer or project manager.

Any adjustment to the system will affect the whole system in some way, hence the term balancing. Balancing is achieved by adjusting the system to get it in line with the specs set down. To make sure you're adjustments are correct, of course, you need to test. So this almost circular process is happening all throughout the job, and you need both patience and a top-of-the-line balometer flow hood. That's the TAB job in a very brief nutshell. We hope it clarifies the need technicians have for a top-notch instrument.

TSI, who also owns the Alnor brand, is perhaps the most well-known and respected name in the TAB and flow industry. A TSI flow hood is one the most accurate and job-tested instruments you can get. The TSI and Alnor brand offers a huge variety of testers for the air balancing field, including standard and "Lo- Flo" flow measuring hoods. Every instrument includes a NIST calibration certificate, meaning that you can trust the stated accuracy with the full backing of a government-certified calibration lab. Considering the small changes in flow that affect the air balancing process, this feature is an excellent benefit to technicians. TSI Alnor also offers a wide selection of flow hood fabric sizes for a range of air registers, measurement accessories like velocity matrices, and handheld instruments like precision anemometers. Overall, TSI Alnor is one of the top-trusted names in flow analysis and balancing. TSI Alnor has two flagship products there: EBT731 and Alnor 6200D.

Testo is one of the top brands in the HVAC field, known for its versatility and top-quality German engineering. Testo is a little bit newer to the air flow field, but their flagship product, the Testo 420 flow hood, gives the TSI line a run for its money. Testo also provides an option for NIST certification on the flow hood and lots of fabric sizes to measure various grille sizes. If you're someone that trusts the Testo name and wants an excellent flow instrument, check out what's on offer from this German powerhouse company. Testo 420 is their most important product in that line.

Kanomax is a Japanese company that is also a major player in the TAB and air balancing industry. Kanomax's flagship flow hood product is in the same league as the Testo model and the TSI model. Calibration is optionally available, as with the others. Kanomax is a bit less well known in the States, but they make a top-of-the-line instrument at an attractive price point. There a few cool features to check out on this flow hood, like a motorized tilt function and some excellent data management options. Definitely consider the Kanomax flow hood when you're looking at all the HVAC flow hoods on sale. Kanomax model 6715 comes now with a wireless features.

Dywer is a sort of "new kid on the block" when it comes to air balancing, but you definitely want to consider what they have on offer. Dwyer actually built an entire simulated building envelope with a contained air flow system inside their research and development facility to design and test their high-tech flow hood. Just a few innovations include: an ultra-light plastic hood that can be handled by a single technician, wireless SMART connection to a WI-FI device for datalogging, app-based data logging and interpretation, and predictive balancing based on algorithmic determinations. If you want a high-accuracy tester with tons of exciting new technology built-in, you want to check out Dwyer. Model SAH-22 is gaining more and more acceptance among TAB service companies recently.

CPS burst onto the flow hood scene with this meter a couple of years ago, and it's been selling like wildfire ever since. Now, to be clear, the CPS Easyhood is not a full-fledged air balancing instrument like the meters above, but it is still incredibly useful. The reasons you can't use this meter for a commercial TAB job are just because it's smaller and doesn't have the calibration-backed accuracy of the hoods we just mentioned. However, smaller jobs are a piece of cake with this meter. It's small enough that one tech can handle it, and all the measurements stream directly to the CPS app for data logging and reporting. Basically, this meter does an excellent job for the price point, but you'll want to get one of the other flow hoods if you have to prove your results to some kind of governing body. CPS ABM-Hood-200 is extremely popular among HVAC technicians starting a new building commissioning service.

The air flow measurement process is relatively easy to understand. A simple version of it goes like this: the fabric portion of the hood gathers all the air coming from the register that you've covered with the hood. At the base of the hood is an air velocity and temperature measuring device (a high-end anemometer essentially), which takes the speed and temp measurements and does a calculation based on the register size you input to give you the flow rate.

The complete process of air balancing is a more extended discussion and requires training to execute correctly, but it is more or less the practice of taking these same types of measurements over many registers in a building and tweaking them so that all the registers in the building produce the flow volume that best makes the whole system run efficiently and to spec. Without a good flow hood to take accurate readings, this process of air balancing would not be possible.

The actual operation of a flow hood is pretty straightforward. Use the fabric portion of the hood to get a seal around the register. This means that all the air coming from the register is going directly into the measurement meter at the bottom of the hood. Because you are capturing all the air coming out (hence the other name for a flow hood), the meter now gets a complete picture of the air flow. The meter will do some internal calculations in real-time and give you a reading for flow. Then you start the comparison process with other grilles that makes up the air balancing process. In principle, this is a simple task, but of course, to do it well, you'll need training and experience.