What size spilt hvac unit for 800 sq ft??

10 years ago

We currently have an 18 year old Freon 2.5 ton split hvac upstairs system (Condenser outside/ furnace in attic). It needs to be replaced, so we had several people come out and give us quotes.

One guy came out and measured our upstairs and got 800 sq ft (which sounds about right) and said we only needed a 2 ton unit. No one else that gave us a quote said we needed a 2 ton. They all just looked at the unit we currently had and said we needed a 2.5 ton unit.

Obviously we would like to save money if possible and a 2 ton unit would be several hundred dollars cheaper, but will we notice a difference if we go from a 2.5 to a 2 ton?

The man who told us to go with a 2 ton said that if we stuck with a larger unit it can cause the unit to have hard stops and starts which is not good for the unit nor for our wallets.

We asked some of the other people who quoted us about switching to a 2 ton and some of them said we might feel a difference. We are used to the 2.5 ton, so we might notice on particularly hot days for example that we are just not as comfortable as we were with the larger unit.

Any thoughts on this? We live in South Carolina, northwest corner. I believe that's considered Zone 2. When I research it, it says we could probably even have a 1.5 ton! So, I just don't know. It's a lot of money we're spending, so I want to make the right decision.

Thanks.

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Comments (4)

sktn77a
10 years ago
1.5 ton - your research was correct. Your cooling requirements include dehumidification in the south eastern states. Both the 2.5 and 2.0 ton units are way too big for 800sqft. Unfortunately, you won't save that much money on the purchase and installation costs by going down in size. What you will get is a much more comfortable system with less indoor humidity and lower operating costs.
Sally Dean
Original Author
10 years ago
Thank you for your response sktn77a.

When calculating the square footage, should the hallway, closets and bathrooms be included? When we measured ourselves, we included all those things and square footage was about 950. During the summer, our master bath gets rather warm because of a big arch window that allows the sun in. Should we account for that room too?
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roadking
10 years ago
Hard to say without knowing more about your home. How much insulation you have in the attic and walls, number and type of windows etc. Did the present unit keep you comfortable when it was operating correctly? Do you have a lot of windows facing south and west with little shade?

I live in central South Carolina and finished off an 850 s.f. upstairs in my last home. Put a 1.5 ton heat pump in and unfortunately it didn't keep up with the summer heat and had to be replaced with a larger unit...so tread carefully when downsizing it might be a very expensive mistake.
mike_home
10 years ago
The area should include all conditioned space (bathrooms, closets, hallways, etc.). I would have thought a 1.5 ton unit would be adequate, but the number of windows and construction may raise the cooling load to where a 2 ton is needed.

Is it possible to install drapes or blinds in the master bath window? These could be closed during the day and opened at night. This would make a significant difference in the temperature during the hottest part of the day.