A/C does nothing upstairs - What now?

livinwellFebruary 18, 2008

I had a Carrier 38TXA 5 ton A/C unit and new furnace installed roughly 3 years ago. I have a 2 story house approximately 1950 square feet in Southern California. The thermostat is downstairs and temperature can be maintained very well on that lower level. The upper level continues to be an oven/ice box depending on the season. I have to run space heaters or fans in the bedrooms most of the year. Is my only option to install a second unit upstairs and if so, what size and how do they go about that? I am looking at tinting my west facing windows, but I'm not sure how much that will help. Any suggestions greatly appreciated. My electric bill is through the roof...

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Where do we start? How old is the home, what size was the old system that this one replaced? 5-tons for 2000 sq ft sounds large to me. Did the installing contractor do a "manual J"? IS this system gas, heat pump or electric furnace? Is there sufficient return on the second floor? If the second floor is not heating I suspect a duct problem. Have you had any renovations done recently like moving walls thay might have contained ducts?

Need more information.

    Bookmark   February 18, 2008 at 5:03PM
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bonanza stu - the house was built in 1967 and I don't know the size of the system that I replaced. Regarding Manual J, I remember them all doing calculations after walking through the home and checking windows and duct work in the attic. None said duct work was required and I didn't act like I had a constrained budget, but I have nothing to show for it and can't vouch that the sizing was as it should've been. I had 4 estimates and all said 5 ton. The furnace is gas Carrier 58CTX, A/C is electric. No walls moved,

Heat is not as much of an issue as the A/C since here in So Cal there can be 5-6 mos that the A/C is needed daily. I set thermostat at 75-78 for A/C but by then it is probably 85-90 upstairs and 65 for heat. Furnace rarely comes on in that mode, so the space heaters are used upstairs.

Thanks for trying to help.

    Bookmark   February 18, 2008 at 10:42PM
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If you have dampers on your ducts I would try to close the downstairs ones a little to try to get more flow upstairs. Also check your attic for bypasses where the air can get around the insulation since leaking air will drive up your bill. How is the attic insulated? Do you have wall insulation? If there is no problems with the ducts and your system,(AC does seem oversized btw) then you probably have insulation/airsealing issues. The upstairs of a house usually has greater heat gain and loss compared to the lower levels. That has to be taken into account both when sizing a system as well as what levels of insulation are needed.
Does CA have rebates for energy audits? Even if not I would get one. Doing that and beefing up your insulation levels would likely solve your problems way cheaper than getting an upstairs system.

    Bookmark   February 18, 2008 at 11:09PM
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You are trying to control two different environments with one controller this always a problem and always will be a problem the question is what do you want to do about it here are a few possible solutions a second system would have been a good idea but too late now so you can put a two zone system this would be the most expensive option but less than the cost of a seperate system you will need to call the contractor. You can try adjusting the airflow seasonally, more air upstairs in Summer and Less in winter you will have to be careful with that because if you don't have enough air going throught the system you can cause some damage see if you have a large damper in line on the largest duct going upstairs a smart contractor would have installed one if you don't you will have to adjust each supply branch also run the fan all the time it doesn't cost that much and it will even out the temps in your home

    Bookmark   February 19, 2008 at 5:39AM
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You guys are great. Thanks for all of the suggestions. I am going to look into the energy audit and see what that uncovers. Gonna try to do something before the summer hits.

    Bookmark   February 20, 2008 at 3:37AM
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