Methods for Measuring Residential HVAC Total System Air Flow
| Residential HVAC Air Flow Methods |
Residential Accuracy |
Confidence/Consistency | Equip. Cost |
Approx. Time Range |
Comments | ||
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Recognized for Grading New Install
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Method 1 | Flow Grid |  |
$$$ * | 5 to 10 | Designed to provide repeatable residential HVAC air handler flow. * – Historically is expensive, new version is much more cost-effective. |
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| Method 2 | Pressure Matching using Duct Tester |
$$$$$ | 8 to 15 |
New equipment is expensive. Takes time to connect duct tester to cabinet, varies based on situation. |
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| Method 3 | Flow Hood | $$$$$ | 4 to 8 * | New equipment is very expensive. Powered flow hood for multiple returns, passive for single return flows. Leaky ducts cause mismeasurement. * – multiple returns can add time, lead to mismeasurement if ducts are leaky. |
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| Method 4 | External Static Pressure & Fan Table | $ | 5 to 10 | A low-cost method provides good measurement of air flow on new clean systems. Is prone to large errors on older equipment if the blower fan is not clean. Must have the OEM fan table for exact blower fan model. | |||
| Other Common Methods |
Methods 5, 6, 7 |
Traverse: Hot Wire, Mini-Vane or Pitot |
$$ | 15 to 45 |
These methods are common in commercial, but rarely used in residential due to the time involved and poor accuracy if proper straight run is not available and full multi-point traverse is not completed. |
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| Methods 8, 9 | Temp Rise / Split | $ | 5 to 20 | Low-cost method to get an estimate of air flow range but is prone to errors due to placing of temp probe in non-ideal location, assumptions. | |||
| Method 10 |
Indoor Coil static press. Drop |
$ | 4 to 8 | This is a low-cost method to get an estimate of the air flow but is prone to errors due to cleanliness of the coil. | |||
