2 1/2 or 3 ton?

[Kev442]

I need to see if my thinking here is flawed from the experts. My 3 ton AC has died, a R22 system. 3 ton is technically correct for my load, but here is where I'm looking for input.
Since the central AC died, I put my old window AC's from the old house in, one upstairs, one down. I now have better cooling upstairs with one ton of window AC than I did with 3 ton of central AC!
Why? Because the setting sun beats on the upstairs front bedrooms all afternoon/evening and the window AC is on 24/7 up there right now. This leads me to think I am better off with a 2 1/2 ton system running for longer periods of time than a 3 ton that shuts off when the thermostat is happy, creating the upstairs hot spot.
I will add that my one ton of window AC is able to maintain a 16 degree temperature difference, 73 inside when 89 and sunny outside. This also leads me to believe 2 1/2 ton is correct.
What say the experts? Thanks!

 

[soob]

You might look into rebalancing your old system or moving the thermostat instead. Right?

I don't know; I'm from Mississippi and I've never, ever, in my whole life thought I needed a smaller air conditioner. I do like the flexibility of window units, though. They can save you a lot on the bills.

 

[rickairmedic]

Kev I would stick with 3 tons and have the stat moved upstairs and have them balance your ducts so that you get AC upstairs. Cold air wants to fall by nature and needless to say will fight the trip upstairs . The trick is to get it upstairs it will find its way back down .

I have sent alot of folks here with 2 story homes with furnaces in their basements to home depot for some of these .


http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053


Most of them were considering a second HVAC system and I asked every one of them if the second floor was warm enough in the winter ( heat vrises ) . The answer was always yes so I sent them after vent boosters for the second floor . I have yet to have one call me back and say they still wanted to spend $8000.00-$10,000.00 on a second system but I have had alot of them call me back and thank me for saving them thousands of dollars.


Oh yeah and while your at it contact your local utility company and see if they have an energy audit program . They are generaly free and they will send someone out to test your homes efficiency and tell you what needs sealed up better and if you need more insulation. I have found in my area 99% of the homes built prior to 1975 NEED insulation.


Rick

 

[Kev442]

I guess I should have added some info about the house too. Built 1995, 2 x 6 walls. Super insulated, I believe I have r45 or 55 in the attic and r 19 in the walls. Low E double pane glass and almost none on the south face. Garage is on the north side for winter wind block, I thought this house out a bit.
I came home at 2 PM and with 1 window AC upstairs running, outside 86 and sunny, inside 73, up from 70 at 8 am. I'm still torn.

The vent booster looks like a great idea, I'm buying one of those pronto.
I was told I need 3 ton so that when it is 100 outside, I can maintain 75 inside. The only problem is that we have hit 100 about twice in the last ten years. High for this year is 94.

 

[HVAC Phil]

If the house is newer, insulation good, the duct work must ****. Any new house i have done has never had more than a 1* difference to the upstairs vs. downstairs. Try this, turn all downstairs dampers back about a 1/4 of way open. Make sure all upstairs dampers are wide open. The room where the t-stat is located, cut that damper to only 1/2 way open. Make all adjustments at the dampers in basement, not at the register. I bet the system will be more balanced.

 

[HVAC Phil]

How many sq ft is the house? My house is 2400 sq ft with a 3ton system, last week with 98* outside, house never went above 70. Unit cycled as normal. I will add, i keep my blower running continuous in the summer months. Keeps the rooms much more balanced.

 

[Kev442]

2200 square feet

 

[HVAC Phil]

3 ton is perfect fo that house. 2.5 ton will run and run on a hot day and most likely won't keep it as cool as you would like.

 

[Kev442]

Quotes came in from my guy. 2 1/2 ton is $60 cheaper than the 3 ton. Ya think he wants me to install the 3 ton?

 

[BadgerBoilerMN]

Danski is right. It could be that the ductwork is undersized, but an extra 1/2ton won't change that. Generally - and ususally - the tinner oversizing cooling and makes the unit run short (no time to dehumidify) all the time arguing that bigger is better and hey, same money. Give your work to the smart guy with a sample of heat heating and cooling load. Or get the loads done by a smart guy and tell the contractors (usually good mechanics) what you want.

http://www.badgerboilerservice.com/images/SampleHeatLoadAnalysis.pdf