Works offline. Every calculation runs on your device, no signal needed. Install the BAS Field Reference app to keep it on your phone.
How to use it
- Measure outdoor, return and mixed air temperature. Mixed air is the hardest — watch for stratification and take several readings.
- The calculated OA fraction is what the unit is actually drawing, regardless of what the damper command says.
- Compare it against the commanded damper position. A large gap means the damper isn't where the BAS thinks it is.
- This only works when outdoor and return temperatures differ meaningfully. On a mild day the maths gets unstable — test on a cold morning.
Background reading: Test an Economizer in Twenty Minutes →
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More where this came from
This calculator comes out of BAS Field Fundamentals — the meter tests, the maths and the failure modes for every sensor, drive and control loop in the building, plus 20 field cases and a browser simulator to practice on.
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