Central A/C - 66 Decibels?

esk0mmMay 18, 2013

Hi there,
We're building a new home in California and need to find a quiet (66 decibel) central air conditioning unit to meet our city's requirements to place them in the side yard. We were actually planning on getting two 2.5-3 ton units to place on either side of a 3100 SF single story house. Our HVAC contractor says that he can't find an A/C unit that meets our requirements. Does anyone know of a 66 decibel unit that would make sense for this application?

Thanks! Eunice

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tigerdunes

Lennox's XC17 AC condenser is advertised as the quietest in the residential market as low as 62 db.

One more example of government nonsense and overreach.

IMO

Here is a link that might be useful: Lennox XC17 AC Condenser

This post was edited by tigerdunes on Sat, May 18, 13 at 9:11

    Bookmark   May 18, 2013 at 9:10AM
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mike_home

Is the city inspector going to measure the sound after the condensers are installed or you going to show him the manufacturer's data sheet? A 66 DBA sound level is really low. Be aware the sound level increase as the size of the unit increases.

Do you have room to put a wood lattice or possibly shrubs around the unit? It would make more sense to try to block the noise then try to find a condenser that meets this low noise specification.

    Bookmark   May 18, 2013 at 10:06AM
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Servicetech

Have your insulation contractor make sure the house is tight like a new house is supposed to be. You would only need ONE 3 ton system if the insulator does his job right. 500-600sqft per ton is a rule that came out in the 60's and if your insulation can't do a better job than they did in the 60's time to find a new insulation contractor. There's no excuse for your NEW house to not be at least twice as well insulated at one built in the 60's.

    Bookmark   May 18, 2013 at 7:57PM
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Servicetech

http://acrightsize.com/files/10_reasons_why_oversizing_persists.pdf

    Bookmark   May 18, 2013 at 9:31PM
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fsq4cw

One of the quieter A/C units would be the Carrier Infinity 24ANB series (up to 21-SEER) at 65db. The Carrier Infinity Greenspeed HP (Up to 20-SEER & 13HSPF) is as low as 58db in A/C mode for a 3-ton unit. Probably any variable speed or 2-speed condenser will be quiet enough.

It should be noted that noise level does not necessarily increase with size; in fact the larger capacity unit may also be the quieter one. A case in point would be where either one of 2-size unites could be installed, such as with Carrier Infinity Greenspeed which is available in only1-ton increments. The larger size may be quieter, as itâÂÂs inverter controlled and fully variable between 40-100% output. The larger unit will run slower, may also be quieter, with less wear due to the slower rotation of the compressor.

SR

    Bookmark   May 19, 2013 at 12:19AM
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ionized_gw

I've seen outdoor units for mini splits rated below 50 dB. Do central units have to be so much louder?

    Bookmark   May 21, 2013 at 2:00PM
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esk0mm

Thanks everyone.
Looks like the Lennox XC17 is going to work for our needs. Thanks tigerdunes! To Servicetech, I definitely hear your point about not oversizing the system. Our contractor was originally suggesting a 3 ton system, which wouldn't have met the decibel requirement. I told him we'd be fine with a 2.5 ton system, and now our problem is solved. We're building a pretty tight home with spray foam insulation and a cool roof, so I think we should be ok.

    Bookmark   May 22, 2013 at 1:27AM
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Servicetech

Super tight homes such as yours often get 1000sqft per ton which is 1/2 what the 500 daft per ton used on homes built in the 60s. If you don't believe that foam and cool roof technology can reduce your load to 1/2 that of a house built in the 60s why pay top dollar for them?

    Bookmark   May 22, 2013 at 7:42AM
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Servicetech

I know installing a single 3 to or 2 one ton units is "scary" because its so much smaller than normal, but your insulation is at least twice as good as normal. I've seen a single 2 ton unit do the job on a house the same size as yours.

    Bookmark   May 22, 2013 at 7:47AM
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ionized_gw

Two things bother me about this situation. First, it does not seem like anyone has done load calculations. Second, why has the contractor not dealt with this sound level situation before? Even if it is a brand new building code requirement, my understanding it that local governments send notice to contractors and have meetings to update then on pending changes.

    Bookmark   May 22, 2013 at 9:01AM
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mike_home

"I've seen a single 2 ton unit do the job on a house the same size as yours."

I would be interested in seeing the Manual J calculation showing a 3100 sq. foot house with a sensible and latent heat load of less than 24,000 BTU. Can you post any details?

We don't know the full story on who is determining the size of the AC units. The buyers may be requesting the units be over sized.

I think the buyers want the units placed on the sides of the house rather than the back. I assume the lot is narrow and the houses are close to each other. This is probably the reason for the sound limitation.

    Bookmark   May 22, 2013 at 9:33AM
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brickeyee

Look and see what the neighbors are using.

Make sure an accurate load calculation is performed..

    Bookmark   May 22, 2013 at 2:37PM
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Servicetech

http://acrightsize.com/files/elephant_in_the_room.pdf

3200sqft on a 2 ton system.

    Bookmark   May 27, 2013 at 7:52PM
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mike_home

'http://acrightsize.com/files/elephant_in_the_room.pdf
3200sqft on a 2 ton system."

I read the article, but I don't see where it states a 3200 sq. ft. house can be cooled with a 2 ton AC system. Can you point to the page number and paragraph?

    Bookmark   May 27, 2013 at 9:40PM
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fsq4cw

"I read the article, but I don't see where it states a 3200 sq. ft. house can be cooled with a 2 ton AC system. Can you point to the page number and paragraph?"

Page 7, "Outdated Training" second paragraph.

SR

    Bookmark   May 28, 2013 at 1:20AM
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mike_home

I found it, thanks for pointing it out.

The article states the author lives in Arizona. It is possible to achieve the cooling load stated, but it is not your typical house construction. I agree with the article in that every installation should start with a proper load calculation.

    Bookmark   May 28, 2013 at 8:17AM
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