HVAC School - For Techs, By Techs Residential Air Balancing & Flow Hoods
Steve Rogers from the Energy Conservatory comes on the podcast to talk about residential air balancing and flow hood accuracy.
Residential air balancing is important because it contributes to comfort in the home. To achieve the most comfort possible, we need to know where the air is going inside the home. For example, some rooms may be more conditioned than others, even if they may need less conditioning than the under-conditioned rooms. A flow hood can give us some data about the airflow in the ductwork; there are cases where dampers may be closed, which blocks airflow and contributes to customer discomfort.
Load calculations can only help so much. Systems require flexibility because air distribution can vary across seasons or throughout the day. HVAC systems won't always perform under design conditions, so it's a good idea to think about customer comfort above Manual J or Manual D calculations.
Flow hoods are some of the best tools for residential air balancing; they can tell you where there is flow and where there is not. However, flow hoods are expensive and may not be completely accurate if they haven't been calibrated correctly. Many manufacturers use a single supply register configuration or wind tunnel for calibration. Many flow hoods use a pitot array, which is a grid that attaches to a manometer. Others use the RPM of an impeller to measure the flow; they also compensate for resistance. Some hoods also use vane anemometer technology. You can typically determine the insertion losses by looking at the hole size.
Steve and Bryan also discuss:
- Pressure vs. velocity
- Air handler location
- Load calculation (Manual J)
- Balancing dampers
- Anemometers vs. flow hoods
- Insertion loss
- Flow conditioning
- Building envelope construction
- TrueFlow Grid
- Accuracy questions about flow hoods
Check out THIS webinar with Steve and Bill Spohn.
Learn more about Refrigeration Technologies HERE.
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