OT: Any Air Conditioner Experts Here

[jghall]

Ok, buying a new house and one that I am looking at has a very nice and brand new 4.5 ton air conditioner.

Which on the surface sounds great. Though several years back I remember reading an article on that too big of an a/c is actually not good.

It causes short cycles, which actually increases utility costs. It also does not get rid of the humidity within the house.

So have things changed? Is load calculation a real issue? Is the above still an issue, or has newer technology progressed to compensate? Is too big of an a/c a bad thing?

Anyone know of a contractor in the Indianapolis area that can assess this for me?

Thanks in advance for the time.

Regards,
jeff

[AngryScientist]

too big of an HVAC system is indeed a bad thing.

this is a decent summary, based on large building, but still applicable.

hire any reputable HVAC contractor to do a load calculation on the house. shouldnt cost you too much, and will be worth it.

http://optimalbuilding.com/files/7_reasons_why_oversizing_is_a_bad_idea.pdf

[malcolm]

I have no idea but only offer this. My house has about 5 units and we paid a company to maintain them for about 10 years. The first 7 years was ok they came out twice and year and all was well. The last few years every time they came out something needed to be done. This last year at the start of summer they said we needed to repace a unit for between 5-7 thousand dollars or they could repair it for 1200 but couldn't say how long it would last. We had been having no issues and the guy was pressing to do the work. I said no and had a friend come out that does HVAC work as part of his job at a bio med facility and he checked the unit and said it was fine. It worked perfectly well all summer and continues to do so. My buddy also said when he was at school the other students were constanly talking about phantom repairs and illicit billing. Be careful this industry is apparently rampant with fraud.

[William]

I have no idea but only offer this. My house has about 5 units and we paid a company to maintain them for about 10 years. The first 7 years was ok they came out twice and year and all was well. The last few years every time they came out something needed to be done. This last year at the start of summer they said we needed to repace a unit for between 5-7 thousand dollars or they could repair it for 1200 but couldn't say how long it would last. We had been having no issues and the guy was pressing to do the work. I said no and had a friend come out that does HVAC work as part of his job at a bio med facility and he checked the unit and said it was fine. It worked perfectly well all summer and continues to do so. My buddy also said when he was at school the other students were constanly talking about phantom repairs and illicit billing. Be careful this industry is apparently rampant with fraud.

Beware....
http://www.youtube.com/watch?v=rK_rkvZeXdU





William

[zennmotion]

I have no idea but only offer this. My house has about 5 units and we paid a company to maintain them for about 10 years. The first 7 years was ok they came out twice and year and all was well. The last few years every time they came out something needed to be done. This last year at the start of summer they said we needed to repace a unit for between 5-7 thousand dollars or they could repair it for 1200 but couldn't say how long it would last. We had been having no issues and the guy was pressing to do the work. I said no and had a friend come out that does HVAC work as part of his job at a bio med facility and he checked the unit and said it was fine. It worked perfectly well all summer and continues to do so. My buddy also said when he was at school the other students were constanly talking about phantom repairs and illicit billing. Be careful this industry is apparently rampant with fraud.

Two words.
Angies List

www.angieslist.com

Best source for who's scammin and better, who doesn't. No more friends recommendations for me without backup from Angies.

[malcolm]

Two words.
Angies List

www.angieslist.com

Best source for who's scammin and better, who doesn't. No more friends recommendations for me without backup from Angies.

Very true. We were happy with this company for years and it was the same guy who always came out, then we stopped seeing him and it was a different guy every time. That is when the trouble started. We looked at angies list afer the fact and they had decent rating, only one other that suggested the same thing we experienced. They only had about 7 entries total. Interestingly after further reasearch this is a common complaint with HVAC compaines, the guys work somewhat like independant contracters so their income is tied to their billing. It's a set up for erroneous charges.

Angie's list is just starting to take off in our community

[shovelhd]

My experience with cooling involves designing datacenters. Fortunately, requirements for people are similar to computers.

4.5T is not a huge amount of cooling. It is the equivalent of 54,000 BTU. You don't say what the square footage of your house is, whether it is one story or two, where you live, whether the house has southern exposure, how the house is insulated, or how cool you like to keep the house. All of these factors and more play into how much cooling your house requires.

I will use my own house as an example. It is a two-story 2200 sq. ft. cape in western MA. Southern exposure between 10am-4pm during the summer. R22 insulation in the attic, which is well vented with eave vents and a full ridge vent. The set temp we like is 72 degrees. There are two five-ton units on separate thermostats, one for the upstairs and one for the downstairs. During the cooling season, we mainly use just the upstairs unit. Only on the hottest, most humid days do we use the downstairs unit, which may equate to 5-10 cooling days out of the season.

[rwsaunders]

Certainly not the only answer, but this might help get you started.

http://www.northernac.com/newcalc.htm

[jghall]

Thanks, keep them coming.

My experience with cooling involves designing datacenters. Fortunately, requirements for people are similar to computers.

4.5T is not a huge amount of cooling. It is the equivalent of 54,000 BTU. You don't say what the square footage of your house is, whether it is one story or two, where you live, whether the house has southern exposure, how the house is insulated, or how cool you like to keep the house. All of these factors and more play into how much cooling your house requires.

Figured some of the above would be applicable, but I could not speak to how the house is insulated other than making a blanket statement that the home was built by a fairly high-end builder here in Indiana and built in the mid-90's.

To the other stuff; 2 story with a finished basement, 2,600 sq. ft. upper 2 levels, additional 1,300 sq. ft. basement, front eastern/back western exposure, lean more toward keeping the house on the warmer side than wanting one that is ice cold.

Thanks again to all.

[Louis]

Unless it's a teeny house, I think it's unlikely that 4.5 tons is too much. Maybe if you were in Minnesota, or someplace like that, but not Indy.

[zap]

Paging :). He's the pro.

[Ken Robb]

If the builder is still around you can probably find what insulation he used. The building department probably has the plans and inspection reports on file.

Failing those options you can probably find minimum specs for insulation at the time it was built which is better than no info.

[shovelhd]

To the other stuff; 2 story with a finished basement, 2,600 sq. ft. upper 2 levels, additional 1,300 sq. ft. basement, front eastern/back western exposure, lean more toward keeping the house on the warmer side than wanting one that is ice cold.

I'd say you're in the ballpark with 4.5T. A professional visit can give you a better idea.