Author Topic: a/c sizing  (Read 528 times)

Offline robstar

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a/c sizing
« on: June 11, 2017, 11:36:03 AM »
Hi Guys,

I just wondering what formula you guys using to size an a/c

Offline walker

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Re: a/c sizing
« Reply #1 on: June 13, 2017, 04:02:30 PM »
a great start would be a heat load calculation.

Offline Admin

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Re: a/c sizing
« Reply #2 on: June 13, 2017, 04:28:03 PM »
That's the safe bet for sure.  I follow the HVAC design sizing but to be honest 90% of the time I divide the square feet of the house by 950 and come up with the same size.  The designers tend to undersize now to improve comfort.

Offline Jorgebaloy

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Re: a/c sizing
« Reply #3 on: July 12, 2018, 12:17:30 PM »
Measure the space: Whether you want to cool just one or two rooms or a whole house, you’ll need to figure out how many square feet the area is. First, measure the length and width of the room or rooms to be cooled.

Most of time, you can find the square footage of your entire home in your mortgage paperwork or property tax statements, which will save you from having to re-calculate. If you do need to get out the tape measure, remember not to include your basement, attic space, or closets.

Calculate the square feet: Once you have the length and the width of the area, you’ll need to multiply those two numbers together to come up with the square footage.

Determine the cooling capacity: How fast an A/C can produce cool air is measured in BTUs (British Thermal Units) per hour. You need approximately 30-35 BTUs/hour for each square foot of space if you live in a warm climate and 50-60 if you live in a cooler climate.

Offline tenletters

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Re: a/c sizing
« Reply #4 on: July 12, 2018, 03:49:56 PM »
a great start would be a heat load calculation.


Typical Internet response. I bet my life your company is not doing heat loads on all retros. If you say you are, I call complete BS.

Offline Porcupinepuffer

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Re: a/c sizing
« Reply #5 on: July 12, 2018, 04:58:17 PM »
That's the safe bet for sure.  I follow the HVAC design sizing but to be honest 90% of the time I divide the square feet of the house by 950 and come up with the same size.  The designers tend to undersize now to improve comfort.

Typical Internet response. I bet my life your company is not doing heat loads on all retros. If you say you are, I call complete BS.

He only pointed out how he comes up with the same answer by doing the square footage method when compared to HVAC design sizing... No need to get angry.
Besides, the units are sold in half ton increments. It's not like we can size and predict what will be perfect for every BTU under every situation.

Offline Admin

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Re: a/c sizing
« Reply #6 on: July 12, 2018, 05:39:56 PM »
Quote
Typical Internet response. I bet my life your company is not doing heat loads on all retros. If you say you are, I call complete BS.

We do about 1000 new construction homes a year and we have a HVAC design for every house.  In alot of municipalities this is a requirement.

Offline tenletters

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Re: a/c sizing
« Reply #7 on: July 12, 2018, 06:54:49 PM »
That's the safe bet for sure.  I follow the HVAC design sizing but to be honest 90% of the time I divide the square feet of the house by 950 and come up with the same size.  The designers tend to undersize now to improve comfort.

Typical Internet response. I bet my life your company is not doing heat loads on all retros. If you say you are, I call complete BS.

He only pointed out how he comes up with the same answer by doing the square footage method when compared to HVAC design sizing... No need to get angry.
Besides, the units are sold in half ton increments. It's not like we can size and predict what will be perfect for every BTU under every situation.
Quote
Typical Internet response. I bet my life your company is not doing heat loads on all retros. If you say you are, I call complete BS.

We do about 1000 new construction homes a year and we have a HVAC design for every house.  In alot of municipalities this is a requirement.

Oh damn no. I quoted the wrong response lol

I meant to quote the, "a great start would be a heat load calculation." post

Sorry  :-X

Offline Admin

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Re: a/c sizing
« Reply #8 on: July 12, 2018, 10:19:30 PM »
No problem!  ;D

Offline walker

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Re: a/c sizing
« Reply #9 on: July 13, 2018, 05:08:52 PM »
a great start would be a heat load calculation.


Typical Internet response. I bet my life your company is not doing heat loads on all retros. If you say you are, I call complete BS.

thanks for the vote of confidence.  My company who knows, I do only service work for them.  On side work, yes I do them, its looks good to the customer.  but as Admin pointed out 9.5 times out of 10 they come out exactly as you'd think they would using rule of thumb.

Offline tenletters

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Re: a/c sizing
« Reply #10 on: July 13, 2018, 05:53:46 PM »
a great start would be a heat load calculation.


Typical Internet response. I bet my life your company is not doing heat loads on all retros. If you say you are, I call complete BS.

thanks for the vote of confidence.  My company who knows, I do only service work for them.  On side work, yes I do them, its looks good to the customer.  but as Admin pointed out 9.5 times out of 10 they come out exactly as you'd think they would using rule of thumb.

I just disagree is all. Doesn't mean yourself or the company does bad work. I really do not believe you're completing a certified heat load on side jobs, unless it's for new housing that is.

It's possible you have a spreadsheet with fill in the blanks like reliance sales staff, but that's not a heat load and often times tells the installer to put a 120k btu furnace and a 1 1/2 ton AC in an 800 sq ft house.

If you actually are doing a real certified heat load, awesome. It looks really good on you.

Offline walker

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Re: a/c sizing
« Reply #11 on: July 15, 2018, 07:08:01 AM »
a great start would be a heat load calculation.


Typical Internet response. I bet my life your company is not doing heat loads on all retros. If you say you are, I call complete BS.

thanks for the vote of confidence.  My company who knows, I do only service work for them.  On side work, yes I do them, its looks good to the customer.  but as Admin pointed out 9.5 times out of 10 they come out exactly as you'd think they would using rule of thumb.

I just disagree is all. Doesn't mean yourself or the company does bad work. I really do not believe you're completing a certified heat load on side jobs, unless it's for new housing that is.

It's possible you have a spreadsheet with fill in the blanks like reliance sales staff, but that's not a heat load and often times tells the installer to put a 120k btu furnace and a 1 1/2 ton AC in an 800 sq ft house.

If you actually are doing a real certified heat load, awesome. It looks really good on you.

I use coolcalc manual J which is ACCA approved, good enough for me.

Offline tenletters

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Re: a/c sizing
« Reply #12 on: July 15, 2018, 11:14:45 AM »
a great start would be a heat load calculation.


Typical Internet response. I bet my life your company is not doing heat loads on all retros. If you say you are, I call complete BS.

thanks for the vote of confidence.  My company who knows, I do only service work for them.  On side work, yes I do them, its looks good to the customer.  but as Admin pointed out 9.5 times out of 10 they come out exactly as you'd think they would using rule of thumb.

I just disagree is all. Doesn't mean yourself or the company does bad work. I really do not believe you're completing a certified heat load on side jobs, unless it's for new housing that is.

It's possible you have a spreadsheet with fill in the blanks like reliance sales staff, but that's not a heat load and often times tells the installer to put a 120k btu furnace and a 1 1/2 ton AC in an 800 sq ft house.

If you actually are doing a real certified heat load, awesome. It looks really good on you.

I use coolcalc manual J which is ACCA approved, good enough for me.

That looks pretty decent actually. I just ran through one quickly. Came pretty close on my house. Good stuff man.