Central AC system One vs Two systems

15 years ago

I have been getting different feedback on my CAC proposals from the contractors. I have a 2 story house plus basement. There is no ductwork and I want to add CAC.

Basically some are in favor of one system with ductwork through the second floor closets. Benefits - cheaper (about 4-6K I am told). Drawabacks - No basement A/C and registers on first floor can only go below a closet on the 2nd floor, not in their "ideal" locations.

Others are in favor of the split up and down system... This requires way more construction (running 2 main trunk lines, redoing the basement ceiling) and adding a Subpanel to my electric.

Can anyone advise me in their opinion is the split system worth the extra cost and what the Pros and Cons are?

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Comments (5)

rkthomas13
15 years ago
I face a similar problem in a house I am now rehabbing. Did your contractors do a heat gain/loss calculation, )known as a manual j in the trade?
I have a 1950 two level plus basement with one rear addition and one side addition, all of which needs to be brought together in one system. I plan to install an air handler in the attic, which is otherwise unused space for the two floors above ground. In the basement AC is easier, because the temperature difference winter and summer is much less, using the stable temperature of the earth. And if you do not plan to use the basement for sleeping space, why worry about it at all?
tigerdunes
15 years ago
landmark

several questions...

what area of country do you live?

how do you heat your home?

what is your electric rate?

adding AC to a two story home can be problematic if you intend to install just one system. if comfort and satisfaction are important, then you should install two systems.

IMO
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landmarker
Original Author
15 years ago
Thanks for the resp's. To answer the questions:

Did the contractors peform Manual J - Not in the estimation process. One stated they would do so

Area: North Mid Atlantic Region
Heat: Oil Furnace with HW Baseboards
Electric Rate: variable between .10 and .15 $/Kwh. Currently at high end of range.

I take it from your posts that if I install once system, the first floor will not get cooled?
uncledave_ct
15 years ago
FWIW, I just had AC installed this summer. It's a mid-60's 2-story in CT with HWBB heat, no existing ductwork. We had options for single system, 2 systems, and high velocity (Unico).

I decided to go with the 2 systems: 1st floor system installed in the basement, 2nd floor in the attic. The reasons were the ability to "zone" the system, not having to give up space to build a chase, and less cutting of drywall.

We had an interesting problem getting A/C to the family room, which is on a slab on the 1st floor behind the garage. Due to the layout, we could not get ducts from the basement to the family room, so instead it's fed from the 2nd floor system, with the ducts run through the garage and into the family room attic. In practice, it works very well, as the family room stays within 1 or 2 degrees of the upstairs, and the comfort level is excellent.

So here's a vote in favor of 2 separate systems.
beth
14 years ago
uncledave_ct. Our situation, including house age, style and ct, is almost identical to yours, except family room is on a slab off of dining room. Yesterday we had a contractor come and look it over to prepare an estimate. He stated that two systems would be very expensive and that we should do one in the attic. My questions are: How have your two systems worked out for you during this horrible, damp crazy summer? Is your basement also air conditioned? Would you do it the same way again?

My house is approximately 2,200 s.f. not counting the basement, which puts it closer to 3,000. Would you be willing to share information about the size and brand of system that you installed?

Thanks.

Central AC system One vs Two systems

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rkthomas13

tigerdunes

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Central AC system One vs Two systems

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rkthomas13

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