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Old 06-25-2020, 08:08 PM   #1
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size of unit(s)


I'm building a 20,288 sf private house. The house is 2.5 stories. It's a private frame and brick residence located in Nassau County, Long Island. How many central air conditioners should I install and how many tons should they be?
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Old 06-25-2020, 08:25 PM   #2
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Re: size of unit(s)


You’ll need a manual J to determine the answer to your sizing question.
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Old 06-25-2020, 08:35 PM   #3
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Re: size of unit(s)


If you can afford to build a 20k sq ft house surely you can afford an engineer to properly design the distribution system and select the right equipment for the job.
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Old 06-25-2020, 08:43 PM   #4
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Re: size of unit(s)


Agree with both Roughneck and user12345a. Best to have the engineer coordinate with your architect too, so that you don't have any "architectural surprises".
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Old 06-26-2020, 05:16 AM   #5
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Re: size of unit(s)


How many would depend on the layout of the house.


What size would depend on how much heat gain the house has.


An engineer or architect should be able to determine all of this for you for a fee.
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Old 06-26-2020, 08:45 AM   #6
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Re: size of unit(s)


The architect reccomends 5 compressors. Three 1.5 tons. One 3 ton unit. One 4 ton unit. This seems like overkill to me.
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Old 06-26-2020, 08:54 AM   #7
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Re: size of unit(s)


Was a load calculation done?
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Old 06-26-2020, 09:41 AM   #8
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Re: size of unit(s)


Less than 1 ton per 1700 sq ft.

Doesn’t sound like he is getting carried away.
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Old 06-26-2020, 04:32 PM   #9
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Re: size of unit(s)


Just don't leave this up to the builder or HVAC sub. Get a qualified architect and/or engineer to design the system.
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Old 06-26-2020, 08:52 PM   #10
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Re: size of unit(s)


Seems like a funny question for a DIY chatroom.
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Old 06-29-2020, 08:08 AM   #11
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Re: size of unit(s)


Would the manual j show the total tons needed or the number of actual compressors needed?
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Old 06-29-2020, 08:34 AM   #12
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Re: size of unit(s)


Quote:
Would the manual j show the total tons needed or the number of actual compressors needed?

The Manual J calculation method is a way to determine heat gains for a zone or a whole house. Figuring out the most efficient and economical way to set up the zones is a job for the pro who designs the system. That must be done before the Manual J cooling load calculations. For a house this size, it will pay to get someone who is very experienced to design the system. What you spend getting a good design will more than pay for itself in what is saved in installation and operating costs. Once the design and layout is done, then the Manual J calculations will determine the necessary sizes for units in each zone.
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