### RE: Change In Enthalpy

I read in an article that 6.66 change in enthalpy is about 400 cfm. What causes a really high and really low enthalpy reading?

Your question isn’t very clear. There’s lots of things that affect enthalpy change, R/A conditions, charge on the unit, outdoor temp. etc. To calculate BTU/hr from enthalpy change one can use the following formula.

BTU/h = 4.5 * DeltaE * CFM

MeasureQuick does have some voodoo magic formula that estimates CFM from enthalpy change measurements, but I’m not exactly sure the formulas they are using to do it.