Manufacturer Extended Performance Data

[rifter1]

The "extended performance" data published by manufacturers is apparently linear. In the back of Manual S they show a linear equation to recreate performance data tables.

When you plot the actual published performance data on a graph, it is also - apparently - linear.

However DuPont published an interesting .pdf that shows R410a after about 105F ambient starts to drop off in a VERY non-linear manner.

http://refrigerants.dupont.com/Suva/en_US/pdf/k05738.pdf

(See page 2).



So what can I conclude except the manufacturer performance data is misleading above 105F?

What do you think.

 

[trashcanman]

I think you should stay within the published data. Outside the "wire" is an unknown territory. Without testing, you just don't know. I would never spec a piece of equipment that has to operate at the very limit of it's envelope. If your calcs are wrong, you can only go down. Pick a unit that operates in the middle of its range, so you have some "wiggle" room, up or down.

 

[rifter1]

That is one of the puzzles I'm trying to solve.

a) An existing R-22, 5 ton residential unit is replaced.
b) The new R-410a system does not cool as well at high temperatures.
c) Why. It seems to keep happening.

I have plotted 30 published extended performance data from a single manufacturer, and found no unit in the past 40 years deviates from the average performance by more than 2,500 BTUs at any outdoor ambient temperature (published data from 75F through 125F).

However I still am puzzled why the performance data are all straight lines, when R-410a clearly loses capacity within the published data ranges.