[jrref]

Originally Posted by Malsua

I just want to chime in a little. I am a licensed, certified, insured and bonded home inspector and I have inspected north of 500 homes here in TV.

In the past, I did a lot of industrial work, including, but not limited to installing boilers and HVAC equipment both commercially and residentially.

There is a method to calculate your home's HVAC requirement, emphasis on the AC, and it's called a Manual J. It is a long, sorta complicated method but it'll come out accurate.

You don't have to do this though as it's already been done for the home you live in. Unless you have altered your structure, the size of the heat pump or AC you have(if you have a furnace as well), is what you should stick with.

I have inspected two homes this year where the home owner was from up north, and wanted the house to be 71 during the day and 66 at night. While not such a problem in January, when they come down in July, it's not going to happen with the original condenser.

In both cases, they got larger units.(i.e. 1 ton larger and 1.5 in the other) In both cases, the units short cycle most of the year(both inspections were in the spring) and the humidity in the home was never controlled properly. The system wouldn't run long enough to get the humidity out before set temp was hit.

The other issue about running 71 degrees while it's 93 with an 80% relative humidity is that every leaky spot in your house will be found after a while as the paint flecks off and the wood trim around the windows and doors starts to rot from all the condensate. Yes, when you sell, your home inspector will find it.

You can typically upsize half a ton without too much drama, but if your current size does not struggle in July, that's the size you should keep.

One final thought. Of all the homes that are 15+ years old and still have the same system? The brand is pretty much always Trane. I have seen one 21 year old Carrier system and probably 25 Tranes that are 20+. My neighbor has a 26YO Trane.

Thanks for all the good information. From what you are saying, further supports getting, if you can afford it, one of the variable speed inverter systems since it will adjust and only use the amount of cooling "power" it needs all the time. Also, you are correct, a manual J should have been done on every home when it was built but nevertheless, we still found systems 1/2 ton to 1 ton undersized. One was a 2600 sqft Begonia model with a 3 ton heat pump system. Nothing special just undersized with smaller ductwork. The homeowner just thought the system was supposed to run a long time and never cool to his desired set temperature during very hot weather.

Here in the Villages, Trane and Carrier are mostly installed so the local HVAC companies have the most parts, trained techs and manufacturer support with these brands. Both companies are excellent but I think once your system gets to about 15+ years, it's probably time to start doing some research on a new unit when you are ready since although your system may run to 20+ years, here in Florida where we run our systems all year long if we have a heat pump, your system probably isn't running as efficient as it could and there may be more efficient systems that will save you money. You just need to investigate. For example, I had a neighbor who ran his 13 SEER and 75% efficient furnace until it stopped for 25 years when maybe he should have replaced it sooner with a 15 or 16 SEER 95% unit and saved money in the long run. This was in NY. The question whether to replace or repair is an on-going debate but at the end of the day it's going to depend on eveyone's specific situation.