HVAC School - For Techs, By Techs Manometers - Short #91
In this short podcast episode, Sal Hamidi of ProductsByPros joins Bryan to discuss what manometers are and how they measure pressure.
Manometers measure pressure at a much higher scale than a micron gauge but lower than that of a pressure gauge; they measure pressure differentials by comparing static pressure to another source of pressure as a reference. Across all segments of the industry, we use manometers to measure static pressure. Static pressure is the pressure of air against the duct, not the actual air velocity. (Static pressure can give you an idea of the airflow, but you need pitot tubes or flow hoods to measure the actual airflow.) We can also use Magnehelics to measure static pressure, but it's just a specialized type of manometer.
We can also use manometers in conjunction with blower doors to perform zonal pressure diagnostic tests. Blower door tests require the technician to pull the house pressure down to -50 Pascals. Then, the technician uses a very precise manometer to help determine the air changes per hour (ACH). Manometers are also invaluable tools in markets with lots of gas furnaces, as they measure gas pressure. You measure gas pressure on the inlet AND outlet side of the gas valve to make sure the pressures are correct.
Every tech should have a regular manometer for everyday use to measure static or gas pressure. Techs on the building science side of the industry should have a precision manometer, which is an expensive but very precise instrument.
Sal and Bryan also discuss:
- Pressure scales (in wc., PSI, Pascals, etc.)
- Absolute vs. relative scales
- Accuracy, precision, and resolution
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