The Flow Box™ is Now Available!
Finally! An accurate and reasonably easy way to measure total system fan flow.
Poor system airflow is one of THE biggest problems in residential HVAC efficiency. That is why proper airflow will be a mandatory requirement for all new ducted A/C systems in California’s 2013 Title 24 Energy Code (eff. July 1, 2014). In most new systems it will have to be tested by a third party (HERS raters).
When the California Energy Commission first expressed concern over standard, passive flow hoods (based on a Lawrence-Berkeley study) was when I first looked into powered flow hoods as an option. The only ones available at that time were based on the duct tester fan and therefore only able to measure up to the capacity of that small fan, far below what is needed to measure tot total airflow of most residential systems, which can go over 2000 cfm.
Most HERS Raters and home performance professionals already have a much larger fan at their disposal – a blower door fan. All they need is a way to attach it to a return grill. That is why I developed the Flow-Box™. A device that turns your blower door fan into a passive flow hood, capable of measuring flows of well over what most 5-ton systems will produce.
This is something I’ve been working on for over a year, now. After several prototypes and much field-testing, I’ve finally come up with a design that is functional and reasonably light. Earlier versions of wood and sheet metal were too heavy and/or fragile. Made from corrugated plastic, PVC, aluminum and lightweight vinyl flex duct, the Flow-Box ™ is accurate, transportable, and durable. It has many advantages over passive flow hoods and at about 1/3 of the cost (assuming you own a blower door). Even if you bought a brand new blower door AND a Flow-Box™, you would pay about the same as for a good passive flow hood.
Cost competitive with a flow grid, it also has advantages over that device, as well. Measuring airflow with a flow grid can be problematic when a system has more than one return grille. Getting a accurate supply plenum static pressure can be very difficult and of dubious accuracy. The Flow-Box™ does not need a supply plenum static pressure and does not affect flow through the return grill that it is attached to and therefore can easily measure a system with multiple returns by taking individual readings and simply adding them together.
It can also facilitate measuring total system fan flow using the plenum pressure matching method.
If you have more questions, just fire me an e-mail at russking(at)sierrabuildingscience.com