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I want to perform an AC Tune-Up on 1, 2 or 3 systems. The results will increase airflows and add 1 or more returns. When I select this on the improved system, it applies these “improvements” to the Base system as well.
Also, changing the ducts from sheet mental to non-metal is not saved.
Why does checking the TXV option lower Delivery Efficiency?
As is stated in the warning at the top of the Detailed Duct Efficiency Calculator, the calculator is a single set of controls that is used for each scenario. Any time you click a Detailed button from any of the duct control sets, you are opening the same calculator with the same set of controls. Each time you open the calculator, the controls are reset using relevant information from the main screen, based on the location of the Detailed button that you clicked. When you close the calculator the calculated efficiency can be copied back to the Efficiency control next to the Detailed button that launched the calculator. This preserves the results of the calculator. Unfortunately this means that if you made a mistake and need to revisit a duct setup, you have to specify it again. We do intend to develop separate control sets for each system in the future, at which time we will remove the warning message.
The TXV option should improve Delivery Efficiency. However, I have just discovered that the formula for the Equipment Efficiency Factor of TXV systems in ASHRAE 152 is only intended for use with fan flows between 200 and 400 cmf/ton. I will amend the calculations to revert to the standard Equipment Efficiency Factor when the fan speed is outside that range. In the mean time, simply leave the box unchecked, whenever you see that it decreases efficiency.
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