Hopefully some HVAC folks will chime in if I deviate too far from reality. In Florida, a so-called "Manual J" computation is required. This is a heat load calculation for the house and considers a large number of different variables such as orientation of the house, the size, location, number, and quality of the windows, the wall and roof insulation, the area you live in, etc. This computation, which by the way is available on-line for your house on one of The Villages or County websites, specifies the heat load in units of BTUs/hour assuming a certain outside temperature and humidity and a desired inside temperature and humidity. Next, a duct work design must be done to make sure that a sufficient amount of airflow can be delivered to each room. When it comes to the actual equipment selection, the cooling losses with the duct work and other inefficiencies must be considered. One "ton" of AC is 12,000 BTUs/hour. A system that is factory rated for 3 tons (36,000 BTUs/hour) may not be sufficient for a house with a heat load of 36,000 BTUs/hour because of cooling losses associated with the duct work and the fact that factory ratings of cooling power may not be achievable in the field. A system factory rated at 3.5 tons may be required for a house with a Manual J calculation of 3 tons, as an example.
OK, so that is the basics. I believe you have a reasonable expectation that the variation in temperature across the house should be no more than a couple of degrees. Assuming you are seeing larger variations than this, your HVAC contractor may be able to modify the duct work to provide more air flow, and subsequent cooling, to the impacted room(s). Regarding the size of your system, I would first check out the Manual J calculation for your house. I don't recall the website but you should be able to find it with some googling. Since the orientation of your house (north/south or east/west orientation) may be different than your neighbors, the heat load calculation, and the selected equipment size, may be different. Also, keep in mind that with the mostly single zone installations and a centrally located thermostat, it can be difficult to maintain completely uniform temperatures across the house. If you have a warm room with southwest facing windows and no window coverings, maintaining a desired temperature may be difficult. Ideally, the Manual J calculation and subsequent duct work design would provide the necessary air flow for southwest facing rooms as that is part of the design process but window coverings, or lack there of, may not be accurately accounted for. I also suggest you discuss your concerns with your HVAC contractor and open a ticket with the Warranty Department. This way you will start a paper trail. Ultimately, I believe some possible rework of the duct work and/or window treatments will be your solution. I believe they are reasonably accurate about equipment sizing. Also, oversizing of the equipment is not a good thing as it may impact humidity control by having the system not run long enough. I hope this helps.
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Originally Posted by under55
I think our heat pump is not large enough.
Curious while looking at all the units in the new neighborhood we moved into I noticed that Munns installs 2.5 ton units.
Sunshine installs 3 ton units. I have talked with a couple of the other owners with the 2.5 units and everyone says the same thing. The rooms the farthest from the Air Handler are harder to get cooled down. I have not had a chance to talk with the owner of a 3 ton.
When I talked with the builder he said it is all figured out differently for each house. But it seems weird that every house that has a Munns unit they are 2.5 and every house that has a 3 ton unit are Sunshine.
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