I sure wouldn't assume they're the same inside by looking at a picture. 13 is pretty low for as much cooling as you're going to need in S Bama.

What does the seer rating have to do with how much it cools? My current unit is a 10 seer.

Both units I'm looking at are 2.5 tons (house is 1200 sq ft). The Rheem does have a better louvered cabinet, I'm just not sure that's worth giving up the extra 2 seer in the Payne.

alabama

I am not a fan of Payne.

If this is a decision driven strictly on cost, then compare warranties. Warranties may be weak if you are subbing out the install and purchasing condenser and air handler yourself.

I would not purchase a new HP system without electronic demand defrost. I would upgrade to a mid range Rudd or Rheem.

these are my minimum specs for a new HP system. both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF
best matching VS air handler
full BTUs in both cooling and heating for your rated size
R-410a refrigerant(same as Puron)
scroll compressor preferred
electronic demand defrost preferred
thermostat with "dehumidify on demand" feature
staged backup heat strips
new and correctly sized refrigerant lineset

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

I would only use authorized dealers for the various brands that provide quotes. see mfg websites.

I would look at Trane/AmStd,Rheem/Rudd,Carrier/Bryant.

I would not purchase a new HP system that did not have electronic demand defrost.

IMO

What is electronic demand defrost? I live on the gulf coast, so I never really see any frost on my outside unit. I sometimes hear my current unit go into defrost mode, but it does this whether there is any frost or not.

I see now that the electronic defrost prevents defrosting when it doesn't need it.

I would like to avoid the variable speed blower, which is why I haven't considered most of the 15 seer units (except the Payne), I just don't like the idea of the fan constantly running. I prefer a more simple unit with less gadgets to break.

I did find another bare bones 15 seer Heil NXH530GKA unitt. I'm not familiar with Heil at all though, would it be better or worse than a Payne?

Avoiding variable speed blowers seems like a strange thing to do. A motor that operates at various speeds is hardly a gadget. Electronic sensors can break but generally solid state electronics are near forever items.

That being said, I'm not sure you need a variable speed blower but I wouldn't necessarily avoid them.

You would be far more comfortable from a humidity standpoint to have a staged unit that runs all the time. You most likely have a leaky house and the RH in the summer is higher than most people would like.

The comment about seer 13 is that you will run your a/c a lot and that is a relatively inefficient system. It makes sense up north where they might run a/c 20 days a year. Since you will run it closer to 150 days a year, you should invest in a higher seer. Obviously seer 8 can keep you comfortable but at what cost. The payback is pretty quick on a seer 15 unit and possibly even worth higher (but not likely given your electric rates).

What tells the variable speed ones when they should run? Would I need a special thermostat, or is there some sensor inside the air handler that tells it what to do?

I did see a seer 15 Rheem PJL series which indeed does have a variable speed blower. That unit runs around $2200 with freight, so that's not too bad. I also notice the Rheems have a factory installed txv valve, I don't even know what that is but they make it sound like a good thing.

I also
notice the Payne is 28,800 btu, while the Rheem is rated at a full 30,000
btu. I guess that's another plus for the Rheem. My current unit heats just fine in the winter, but it has a hard time keeping up during the summer, I think I need all 30k of those cooling btu's.

There is (usually) a control inside the blower that sets the variable speed. Mine operates by starting slow for a while to dehumidify, then speeding up to for more cooling. When the compressor shuts off, the fan runs on low for a few more minutes then cuts off.

No special thermostat, though I use a 7-day programmable.

'Dehumidify on Demand' thermostats measure the humidity in the home and run the system to lower the humidity. They 'communicate' with the blower unit to turn on the system and run it on low even if the temperature is already good. This extracts more humidity which gives you more indoor comfort at a higher temperature.