HVAC Question

[TexasAg2002]

How many square feet should 1 ton cool in a 4 year old house? I'm wondering if my unit is big enough for my house.

[elliscountyhog]

I didnt think you could get a central unit in a 1 ton the smallest we sell is a 1.5 ton which cools anywhere from 500-800sq ft.

[ballisticbudda]

Get a professional load calculation done. Rules of thumb went out the window when building components became energy efficient. That is if the house was built to standards.

[TexasAg2002]

I have a 2 story 2450 sf house with a 4 ton unit. I am trying to see if the unit is big enough for the house or not. Its hard for us to keep the upstairs cool unless its set on 73 degrees. just thought that was a little odd.

[elliscountyhog]

I have a 2 story 2450 sf house with a 4 ton unit. I am trying to see if the unit is big enough for the house or not. Its hard for us to keep the upstairs cool unless its set on 73 degrees. just thought that was a little odd.

Depends on how the house is set up but sounds like that could be the case and it is pretty common problem. Find a good company that can do a load calc. on the upstairs is the best way to find out.

[charliem714]

A good rule of thumb is 1 ton for every 500 square feet. Remember this is just an estimate. Depending on the codes your house was built under you may give of take.

[ballisticbudda]

Sounds like a Centex home. Lots of them in Killeen, the builders won't give the AC contractors what they need in order to keep the houses comfortable. I've seen 10 degree temperature differences going from room to room. Basically, it is an air flow (duct) issue. The cost to fix the system without resorting to duct booster or fans stops most folks. That is why I see window units in brand new homes.

[mikemorvan]

Two story's and one unit is a bad situation no matter what the tonnage is. Get a professional to check it out. It'll be money well spent.

[elliscountyhog]

Depends on how the house is set up but sounds like that could be the case and it is pretty common problem. Find a good company that can do a load calc. on the HOUSE is the best way to find out.

Fixed it

[TXBowhunter2009]

I have a 2 story 2450 sf house with a 4 ton unit. I am trying to see if the unit is big enough for the house or not. Its hard for us to keep the upstairs cool unless its set on 73 degrees. just thought that was a little odd.

That is a common problem with 2 story homes that have one system/one thermostat. Heat rises, cold falls. Changing thermostat location can help, however, it may also cause problems in the winter when the heat is running. I work for an AC contractor in Austin and personally run load calcs. A 4 ton system in a 2500 sq ft home is not uncommon. The best way to cool a multi-level home with one system is with a zone-damper system (2 t-stats, 2 motorized dampers that open when they're t-stat calls for cool/heat). This could possibly be added to your home with little or no modifications to your home. Get with a liscensed contractor, have a Manual J8 load calc run on your home, and look at zoning options or possibly replacing your 4 ton with 2 smaller systems. Shoot me a PM if you have any questions.

[TexasAg2002]

Thanks Everyone for the help! Hopefully we can get it fixed.

[Codie]

Everything I read on the internet said about 500-600 square feet per Ton of AC System, but my grandad was in the HVAC business for 45 years before he retired and he told me that was a bunch of bull. It all depends on the houses build efficiency. We had 3 different HVAC contractors tell us our 3.5 ton unit was going to need to be replaced with a 4 - 4.5 ton unit after we added on an additional 575 square feet to our home back in January, making it 2,175 square feet heated/cooled instead of 1,600 square feet heated/cooled. They all said if we didn't our electric bills would sky rocket. We chose to try our 3.5 ton unit for a while and our bills have not changed a bit since adding on.

[gargetter]

Two story's and one unit is a bad situation no matter what the tonnage is. Get a professional to check it out. It'll be money well spent.

x2

[bowhntrmatt]

These load calcs are usually pretty accurate if done by a pro.

That said, I had to get one for a two-story house because the owner wants to be eligible for all the rebates out there. The power company guy that did the load calc told me this:

The 665 Sq. Ft upstairs with 8 ft cielings would need a 2- ton unit.

The 1990 Sq. Ft. Downstairs, that included a 1000 Sq. Ft. living area with a 26 Ft. cieling peak would only need 2.5 tons. His reasoning was that the upstairs would pick up the slack from the downstairs unit.

I gotta find a way around this, because I don't care if that house is built inside a Yeti cooler, there is no way in heck the units he calculated would work!

[muzzlebrake]

I have a 2 story 2450 sf house with a 4 ton unit. I am trying to see if the unit is big enough for the house or not. Its hard for us to keep the upstairs cool unless its set on 73 degrees. just thought that was a little odd.

3/4 cfm per Sq ft is a good rule of thumb to determine if you have enough for the air side, assuming the construction is tight and has adequate insulation and the unit is delivering cold enough air. A good system should be able to blow 400 cfm per ton with DX cooling. If your unit is only blowing 1600cfm then you may be a bit shy on air volume and sensible cooling capacity.
Not knowing how your system is laid out it's hard to say but something I have seen on several occasions is lack of return air to the upper level rooms causing the unit to pull all your cold air downstairs. Cold air falls pretty fast.
A single system serving both levels is less than desirable IMO assuming that's what you have.

PS:
I work for an MEP consulting Engineer and load calcs and design is my business ----for the last 40+ years.
If I had the equipment MFG and model numbers I could look it up at work Monday and see what capacities you have available.