Architectural Designs

A/C troubles in a Brand New House, please help..?

Hello Folks.. I'm living in a 18 month old house with 2370 Sq Feet living area. The living & dining rooms, kitchen & breakfast rooms have 12 ft. ceilings, the rest of house has 9 ft. ceilings. There is a 12x14ft bonus room and full bath upstairs above my garage. My A/C unit is only 3.5 tons and there is only one unit for the whole house but there is a thermostat in the master bedroom downstairs and a thermostat upstairs in the bonus room. The evaporator in the attic is a 4 ton (13 SEER unit). We have had the A/C folks out here DOZENS of times trying to get the system to cool the house properly. The worst problem is upstairs. By 12 noon on a typical southern summer day (Louisiana) it will be 80 degrees and will get as high as 84 degrees by 2pm if the outside temp is in the high to mid 90's, even though the unit will run non-stop during the day and nearly all night some nights. The most unusual "fix" they have tried is to replace the Blower/Furnace with a 5 ton unit in order to increase the air flow to at least 1400 CFM (prior is was less than 1200 CFM). Since they changed the blower, downstairs doesn't seem to be a big problem but upstairs continues to be a problem. BUT, it seems that the Humidity level is Way too High.. It never gets below 60% relative humidity and will frequently get as high as 65% depending on outside humidity. From everything i have read, 60% is too high for indoor humidity levels. Could this be caused by forcing 5 tons of air through a 4 ton evaporator? The A/C company has begun to refuse to work on this issue any more other than offering to Upgrade my compressor to a 4 ton but they want me to pay them $1,000 for the upgrade. They claim this will fix everything because the air will be MUCH cooler. However, a neighbor of mine had this done to his identical floor plan and he is STILL having trouble cooling his bonus room. The A/C company and the general contractor are now being hauled into court by several residents of my neighborhood with similar cooling issues that they can't seem to get resolved. Can someone offer some advice or insight as to these problems? Thanks! Al Is 60% relative humidity TOO High for indoors? What SHOULD the humidity indoors be? Can anyone tell me what an Acceptable humidity level would be in Louisiana with a properly functioning and properly sized A/C unit? I'd just like to know just how far off mine is and I am very concerned with mold and mildew growth and inviting termites with the high humidity level.. Thank You for your time!

Public Comments

1. To boil this answer down. Keep everything in writing that you can recall about your current problem. Notify the original a/c company and contractor that you are not satisfied with their work and consider them negligent by mail and that you are going to fix the problem. Go out and get three reliable a/c contractors and get their recommendations with supporting engineering. Pay for the estimates. Hire a lawyer. Hire the middle bid and have them do the work. Relax in the comfort of a properly installed a/c system. Sue.
2. my father, an AC dude would say..you need another unit. Most new 2 story consturction, here in TX anyhow, have 2 units. One for upstairs, one for down...esp at that size. We also had a solar powered attic fan to help with the heat- it really worked. You may need to shade your unit as well...our last house was new construction and the lack of trees/ shade made the unit work overtime...plant some shrubs near it to help cool the u nit. Also- some units have a 'sweater' of sorts on them..esp the ones w/ heat pumps- it is a wrap of insulation - dad removed ours and that helped too...
3. first you need more return upstairs second have they adjusted your zones? you have a zoned system third do you have a supply plenum on the end of your inside unit or did the dummies run the upstairs ducting right off the allstyle coil and finally if they change out the compressor they need to change out the evap coil or install a txv to sum it up one system two floors is a bad idea just because it puts out enough cfms for Square footage do not mean it will work well they do it all the time cheapest contractor squeeky wheel gets the grease pay for a second opinion get it in wrighting your issues
4. The a/c condenser(outside unit) is not large enough. Most builders use 600 sq ft per ton. I've always used 500. Custom home builders go as low as 400 sq ft per ton. Considering all factors, I would think that splitting the house into separate cooling areas would be best. 3 tons upstairs and 2 down. Good luck and God bless
5. I have sold heat and air for over 30 yrs. and I usually use 400 sq. ft. per ton, so I would have give you 6 tons total. With this formula, I have NEVER had a complaint, but, would have to see the floor plan to tell you what size units go where. And the reason your humidity is high, is because your unit is too small. And by the way I use 2000 cfm blowers on my 5 ton units. Also that half ton upgrade is a joke, It's not gonna make much difference because you need 6 tons total. You need another a/c guy, because I gaurantee you, any a/c person could tell just by looking at your house it's gonna take more that 3.5 tons, if they have ANY experience at all. Let me know if I can help.
6. What you need to do is add another unit.
7. you need a new unit that is undersized id add a 2nd 3-4 ton unit
8. call a repairman you are not qualified to work on it and you may get electrocuted mark k