I did a blower door test with the wrong ring setting on my DG-700. Is there a way to calculate the correct reading?

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Yes, there is.  Channel B of the DG-700 is actually measuring a pressure at the flow sensor of the fan and converting the pressure to flow based on the Devise and Configuration settings on the gauge.  Appendix B of the blower door manual has Flow Conversion Charts that allow you to determine what fan pressure the gauge was reading during the test.  Here is an example that will demonstrate the process.  Let’s say you recorded a reading of 3736 CFM and had the DG-700 configuration set to Open.  On your way home you are thinking that the home should have been much tighter and you realize that you actually had Ring A installed on the blower door fan.  Here is the process to find the correct reading:

  • Follow down the Open Fan column until you reach 3736 CFM
  • Follow across to the Fan Pressure column and you will see that you were measuring a fan pressure of 60 Pascals during the test
  • Follow across to the Ring A column and see that 1400 CFM is the correct reading

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