I have been following the discussion on system sizing on another thread for 10 pages worth. In it, several of our most knowledgeable posters bring up differing opinions. Teddy Bear argues for sizing for peak load, and of course including a dehumidifier in the system to deal with the consequent humidity problems.
Dash said "Sizing for peak load ,will likely oversize every time,then you will need a dehumidifier".
It occurs to me that the problem requires *two* AC sizes, and that might explain some of the dissent. You must size for decently high runtimes, to do otherwise will practically guarantee low energy efficiency and poor humidity removal. This is the Manual J philosophy as I understand it.
But... there is a peak load condition which many people object to, where Manual J might lack the sheer power to 1) cool down temperatures quickly, or 2) cope with an unusually high number of people in a party, or other legitimate concerns. (Of course poor installation design, leaks or craftsmanship may *also* destroy peak power, I am assuming the installation does not have these problems.)
It seems the solution which satisfies all these legitimate concerns, is some form of a two-stage system. The 1st stage has the responsibility for high runtimes and good humidity removal, and the 2nd stage is just there for the peak load conditions. Of course it is costly, but performance-wise is this not the solution to the sizing problem?
Regards -- P.Student
P.S. This does not eliminate the objection Teddy Bear states, that no AC system on earth can control humidity in mild weather when it is not running. I'm just trying to find an objective solution (however costly) to the argument about AC sizing. Clearly there are a lot of less costly solutions to be applied in many situations, too.