Its really not that complicated if he is within a half ton either way it will be close enough, and he probably is. Load calcs in general are a waste of time and money, what if your load calc said a 39,000 BTU an hour ac system is needed. You would have to buy one higher or lower than that because if you go shopping for a 39,000BTU unit you won't have much luck finding one.

 

Get a new contractor. If he did not do a load calc after you asked for one, he doesn't know how. That ios NOT a contractor you want to do business with.

Either that, or click the link on this page, download the software, and run your own.

I'd get a new contractor.

 

trust your contractor? i dont want to so no for sure but i'de do some more checking. you can do your own heat load/loss calc by clicking the bullseye at the top of the page but we do them on every job for our customers. heck i thought they hired me cause i was the pro with the answers not just eyeballing and guessing. get a few more estimates.

 

if you go shopping for a 39,000BTU unit you won't have much luck finding one.

Pretty easy to put together a system that produces 39,000 BtuH, just choose the airhandler and condenser from the manufacturer's extended ratings guide, or from the ARI website.

A load calc that is 1/2 ton off is no big deal, but I have seen contractors "eyeball" houses as much as three tons off on a 4 ton load. And my own house in Oklahoma was ONLY 1 ton oversized, but was uncomfortable as any house I ever lived in.

 

I'm in the process of doing a replacemet A/C. My contractor had no problem with doing a load calculation. In fact, one of the reasons I chose the contractor that I did, was because he said he would do the calculation. I don't think my system was sized correctly when it was first installed, so the load calc was very important to me. I also got tired of hearing "if you like 3 tons, you'll love 4". It doesn't take much research to figure out that's exactly the wrong way to do it. Especially in the east (high humidity). All the posts from the pros on this board will tell you the key is to pick a good contractor. That's easier said than done. It actually takes some work to figure out the right questions to ask.

 

Heeeeeeeeeeeeeeeeeere's Bama

 

Do you feel that the existing size of your equipment was suffuceint for your home ? if so then so will the new one of the same size, any contractor that needs to do a load calc on such a standard type house probably doesn't have enough experience doing this kind of work. ( this actually applies to non standard houses as well) I would be embarassed if I needed to do a load calc to size a piece of residential equipment. gees o man c'mon U got to be kidding me this isn't rocket science no matter how hard you try to make it look like it.

 

Do you feel that the existing size of your equipment was suffuceint for your home ? if so then so will the new one of the same size, any contractor that needs to do a load calc on such a standard type house probably doesn't have enough experience doing this kind of work. ( this actually applies to non standard houses as well) I would be embarassed if I needed to do a load calc to size a piece of residential equipment. gees o man c'mon U got to be kidding me this isn't rocket science no matter how hard you try to make it look like it.

If you refuse to do a load calc for a customer who wants one, you are a loser. If you think you can eyeball a load on every house, you're an idiot.

You might think what you do is not rocket science, but then you are doing it wrong.

I was a contractor and service tech for more than 15 years, and worked in the industry for more than 20, before becoming an engineer. And let me tell you this, it is closer to rocket science than even I thought it was.

Maybe you live in a part of the country where humidity is low and any size unit works good? Or maybe you live in a part of the world where people don't recognize comfort? Or maybe, just maybe, you are an idiot?

I don't know for sure, but I am willing to bet that one of those is correct.

 

None of those are correct, though I will agree that maybe everyone couldn't do what I do with the same amount of precision and accuracy (100%) but I know that I canand always do.

 

Uh, huh.

Try this one:

1550 square feet in Norman, OK. 18 inches of wood cellulose in the attic, 5.5 inches in the walls. Double pane glass, on a slab, 3 bedroom, 2 bath.

Give it your best shot. Need more info? Just ask.

 

Eddy

Wrong hill to die on, seriously.

A world of shit is headed your way if you continue on this kick.

 

And what temperature and relative humidity would you like to hold a 1% tolerance to sir ?

 

I can't look.

 

Now when I post the correct answer are you going to fess up or lie to make me look bad ?

 

I would like to hold 72ºF, and . . . . .oh, let's make it easy on you. . .50% RH.

I have a family of four, two boys (13 and 10) and two large adults.

 

Bamacracker is a man of his word.

If you get it right, he'll admit it.

 

Do you feel that the existing size of your equipment was suffuceint for your home ? if so then so will the new one of the same size, any contractor that needs to do a load calc on such a standard type house probably doesn't have enough experience doing this kind of work. ( this actually applies to non standard houses as well) I would be embarassed if I needed to do a load calc to size a piece of residential equipment. gees o man c'mon U got to be kidding me this isn't rocket science no matter how hard you try to make it look like it.

If for no other reason you should run a load calc and keep it in the customer file in case you get dragged to court. I've been surprised by equipment sizes from my load calcs occasionaly. I run those twice, they come up the same, I put them in and get good feedback. Every time a system is oversized you screw your customers' power bills.

 

Do you feel that the existing size of your equipment was suffuceint for your home ? if so then so will the new one of the same size, any contractor that needs to do a load calc on such a standard type house probably doesn't have enough experience doing this kind of work. ( this actually applies to non standard houses as well) I would be embarassed if I needed to do a load calc to size a piece of residential equipment. gees o man c'mon U got to be kidding me this isn't rocket science no matter how hard you try to make it look like it.

WOW!

 

Actually, most of the older guys here already know the answer, cause I posted it here about 4 years ago. I also posted it in other forums as well. In addition, I have photos, and the load calc I did before rebuilding the A/C to my own specs.

 

2 ton, 2.5 ton coil, 900 cfm

 

Everyone stand back.

This only happens every once in awhile, and you don't want to get splattered.

 

Need more info? Just ask.

Yes ,please.

 

Well dang! You only undersized it by 1/2 a ton! That ain't too bad, since the original "expert" put in a 3 1/2 ton unit on a 2.5 ton load, and the house was so uncomfortable we hated it. I finally installed a 3 ton, 2 speed compressor, and converted it to heat pump. It was still oversized in cooling (maintained 67 degrees on a 107º day) when on high speed, but the humidity control from running in 1/2 speed was awesome.

The load calc called out 31,650 total capacity.

But, the truth is, you did not meet the challenge you threw down for yourself. The two tons you specified would have me calling you out to replace or correct it.

Perhaps it is not rocket science, but you are NOT doing it correctly.

 

Now what you don't know sir is who is right or wrong, you said that I undersized by a half ton this must mean that on a design day your unit is running full out all the time correct ? if this is not correct then you don't know how the 2 ton is going to perform because you have not maxed out the one you have. And without looking I doubt that the design temp is 107 degrees.And isn't it standard practice to be under than over and don't you think the 2 ton with a 2.5 ton coil would provide dehum.

[Edited by fat eddy on 02-25-2005 at 09:45 PM]

 

Good clean healthy debate between the pro's. I respect that. A cold one for everybody in the room. But what size AC and heating unit do I need? Who you callin old fat eddy? Well maybe I'm a little old...