Need advice re installing new AC

13 years ago

I'm looking to install a new central heating and air conditioning system in my home. It is in Los Angeles, built in 1926, has two stories, and is about 2,400 square feet. As a result of a remodel done by a prior owner in the 1990s, the house has a central air and a furnace, but no air conditioning.

I have received five or six quotes from the relatively low end ($7,900 for Bryant Legacy series furnace, coil, condenser, some duct work but no zoning) to what I consider to be the very high end (about $20,000 for Carrier infinity series furnace, coil, condenser, some duct work and zoning). My feeling is that my wife and I will own this home for another 3 to 5 years, and then try to move to something nicer. So, I'd like to find a good quality system that is reliable, reasonably quiet, and won't break the bank.

First, do I need a furnace that is rated higher than 80% AFUE?

Second, how important is it to go above 13 SEER?

Third, is a condenser that is louder than 75 db too loud? [I know this is a bit subjective.]

Fourth, how will the almost 20 year old duct work in the house affect the choice of a furnace and/or air conditioner? [I intend to change the duct work under the house, but I am not going to change the duct work behind the walls.]

Five, what benefit is there to having a furnace with more than one speed?

I recognize that most of all of my questions are probably pretty basic to people who know something about heating and AC, but I'm not one of those people and I'd appreciate some simple and straightforward responses. Thank you.

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Comments (3)

tigerdunes
13 years ago
Many

" As a result of a remodel done by a prior owner in the 1990s, the house has a central air and a furnace, but no air conditioning."

That statement is in conflict. House has central air but no AC.

Start with a load calculation for correct sizing.

To your questions.

1. No. I would suggest an 80% eff two stage var speed furnace correctly sized.

2. SEER is all about savings. For LA, I would want 15 SEER minimum, your choice though.

3. 75 Db is relatively quiet. No higher though. You want a condenser that has a compressor sound blanket for noise control.

4. Good ductwork system is all about size, design both supply and return plus insulation qualities. How many returns do you have on each floor? It will be difficult to have consistent temperature from floor to floor with just one system unless you add a zoning control. Of course that would come with a cost. Do you have damper control on the supply trunk lines between the floors? Always suggest a dealer thoroughly inspect ductwork system.

5 CFM speed adjustment is in all furnaces whether single stage or two stage. I recommend a two stage furnace. Of course you will need a true two thermostat for best operation.

6. I always recommend a pleated filter media cabinet for indoor air quality and protection of blower motor and evap coil.

IMO
mike_home
13 years ago
I assume the duct work in the walls is made out of sheet metal. There is no need to change it provided it is of the proper size. Any flexible duct work under the house should have a minimum of R-8 insulation and be sealed.

FYI Bryant and Carrier are the same equipment with different labels. The Bryant Evolution is the same as the Carrier Infinity.
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manyacquestions
Original Author
13 years ago
Thank you for the responses!