quote:

Originally posted by 4MUL8R:
Vendor B did manual J at 92 F to calculate 1/2 ton smaller systems. When temp was raised to 100 F and recalculated the system size went up 1/2 ton.

With most days being well below 100 F here, I can't see giving up 1/2 ton lower capacity and all the advantages of being well matched to actual loads.

Given that, I would stay with the exact same size you have. It is REALLY uncomfortable if you like your house at 74F and it's 78F inside because the a/c's can't keep up. when it's hotter than hell outside. If you haven't had any humidity issues with the size you have now, then you shouldn't in the future by staying with the same size.

Looking at historical averages and the table of HVAC data posted on this thread, I can see why Manual J temperature is 92 F.

quote:

Originally posted by 4MUL8R:

Looking at historical averages and the table of HVAC data posted on this thread, I can see why Manual J temperature is 92 F.

Using something above the recommended design temps equates to oversized equipment for a majority of the time. This equates to high humidity, especially during low load conditions with high humidity ( exactly VA weather ). Our comfort range is dictated directly by the humidity. Thus reason everyone ( well most )sets the thermostat higher in the winter and lower in the summer to offset the humidity effect on us.