That is a 2.5 ton unit.

The 030 is the BTU/hr.

Another thing to consider is that houses in Texas are designed for max of 30 degree difference.

If it is 100 degrees outside, with no humidity, it could get to 70. If your wet bulb temperature starts rising, you'll start having issues. The water takes more energy to drop out of the air, reducing your ability to cook the air down as much.

~egon

Just wanted to let y'all know what I found. I ran a new load calc in Wrightsoft (same he had done) and used all the same criteria they did for building materials and got 2.4 tons as well.
The design criteria follows the city weather data in the software and it was 97 outdoor and 75 inside with a 50% humidity for cooling.
The only real issues I had with their calc was they had the duct systems chosen as "notable" sealed which I rarely ever see done in the field, they had the house as "semi-tight" which again we don't always see and they changed the SHR (sensible heat ratio) from the default .7 to .83 which effectively chooses a smaller unit. I don't agree with the results of my load calc or theirs. Could it be a glitch in wrightsoft? Who knows.
One other thing to note is that when I am choosing a system tonnage I go to a software that de-rates the unit for desired outdoor and indoor temperatures. Essentially if the load says I need a 2.5ton I go into the software and find the unit that is 2.5 actual tons at 102 outdoor and 75 indoor. I guarantee it won't be a 2.5t sized unit. Lower the desired indoor to 71 and it changes even more. I don't have that for Lennox, only the brand I sell.
In BCS the city hasn't started requiring load calcs, blower door testing or energy audits yet but I hear other towns in Tx do require such things. In my 20+ years experience there's no way in hell regardless of what the load calc said on his house that I'd put a 2.5t. I would have likely put a 4ton.
It sucks for him as the data they are going by is what they've got to work on and it appears as though they executed it as they interpreted to be correct.
The other thing you've got to be mindful of is ensuring that what was designed (on the house) is what's actually executed even though your job is only the hvac. I've had new houses where the blown in insulation guys missed the first three feet of ceiling but had R38 everywhere else, I've had houses call for plywood sheathing that didn't get installed, I've had houses change the stud size from 2x4 to 2x6 and vice versa, I've had spray foam guys miss entire joist cavities. If you don't catch these things and the house isn't cooling it can cause you to pull your hair out. I'm almost bald so I have to be mindful.
I'm hopeful that Tilden puts data aside and helps their client out. I'll be of any other help I can.

I live in one story 2584 sq ft house and have one 4 ton and one 3 ton

Really appreciate the feedback. Our builder is supposed to come back with a solution by the end if this week. Hoping they will bite the bullet and replace the current unit with a 4 ton unit

Are you me???? I have almost the exact same thing.

Jason_InfinityRoofer said:

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Dr. Venkman said:

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It not cooling the house is all the proof you need that it was done incorrectly. Rule of thumb is 1 ton per 500 sq ft. so 2.5 tons on 2518 sq ft seems way off.

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I have to respectfully Disagree. There is no "rule of thumb" in 2022 when dealing with Hvac. We have science. The fact that the AC wouldn't cool past 77 when it was over 100 degrees yesterday is actually a pretty good sign that his unit is sized correctly or not, who knows without a lot more info. . We have design temps, and 100 degrees is well outside of it. What is the Op design temp, should all be on the Man J.

If they arrived at 2.5 tons from a man j on a modern standard build house of 2500 sq ft, then we need to know what assumptions were made and where you are located. It won't fly in texas….anywhere.

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I don't know. Sure, we have science for load calculations. But, at the end of the day, it really isn't an exact science when you take it down to the individual house like you're claiming it is. As AgAcGuy laid out, several assumptions are still made in these calculations. Anytime you make assumptions, you're opening up more room for error.

uncover&humpit said:

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Really appreciate the feedback. Our builder is supposed to come back with a solution by the end if this week. Hoping they will bite the bullet and replace the current unit with a 4 ton unit

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4 ton may be worse. You might end up with short run times, this removes less moisture from the air. Not a good thing in Houston.

Also, with more moisture in the air, you'll have to get the temp reading on the t'stat lower to feel as comfortable.

BenTheGoodAg said:

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Jason_InfinityRoofer said:

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Dr. Venkman said:

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It not cooling the house is all the proof you need that it was done incorrectly. Rule of thumb is 1 ton per 500 sq ft. so 2.5 tons on 2518 sq ft seems way off.

---

I have to respectfully Disagree. There is no "rule of thumb" in 2022 when dealing with Hvac. We have science. The fact that the AC wouldn't cool past 77 when it was over 100 degrees yesterday is actually a pretty good sign that his unit is sized correctly. We have design temps, and 100 degrees is well outside of it. What is the Op design temp, should all be on the Man J.

If they arrived at 2.5 tons from a man j on a modern standard build house of 2500 sq ft, then we need to know what assumptions were made and where you are located. It won't fly in texas….anywhere.

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I don't know, Jason - let me preface this with how I normally really value and agree with your opinions, but "100 degrees is well outside of design temperature"? Where are you living in Texas? I'm in the northern tip and still saw 106 multiple times this week. And you mean to tell me there's no margin in HVAC design? And while a rule of thumb is not proper design, it definitely is outside a typical ratio of square footage to tonnage. My $.02, it smells like the undersized both from a square footage standpoint, and from a performance standpoint. Maybe the calcs are using the ridiculous DoE requirements (78* when home, 85* when away, 82* when sleeping).

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First, I'm not an HVAC dude. No surprise there. I only know what I know because I always have to follow behind all of my contractors when I had my house remodeled. That included manual J stuff. Anyway, if you're in a spot that regularly sees those temps, then I'd imagine your particular design temp for hvac work is a lot higher than say someone that lives in Virginia. For Houston, if you're going with average temps and you roll in your insulation values and whatever, there will be extreme days that the AC just can't completely keep up with. That was my point with all my long winded verbiage.

Either way, I am in agreement that a standard house build of 2200 square feet sporting a 2 ton unit is going to be undersized. The options are insulate a lot better or put in a bigger unit.

Also, based on the info from the other thread by ACGUY, I am incorrect with my previous post. So, yeah, I was wrong and I retract those bits and pieces.

EMY92 said:

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uncover&humpit said:

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Really appreciate the feedback. Our builder is supposed to come back with a solution by the end if this week. Hoping they will bite the bullet and replace the current unit with a 4 ton unit

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4 ton may be worse. You might end up with short run times, this removes less moisture from the air. Not a good thing in Houston.

Also, with more moisture in the air, you'll have to get the temp reading on the t'stat lower to feel as comfortable.

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My house is a bit larger at 2680 square feet, but I have a 4 ton downstairs and a 2.5 upstairs. While I don't know anything about a/c sizing, I have a lot of area under vaulted ceilings That said, I absolutely had short run times on my downstairs unit in mild weather, but when it went out I replaced it with a 4 ton 2-stage unit. It works infinitely better.

That's a different scenario. The two stage compressor operates as a "smaller" unit until it needs more capacity.

htxag09 said:

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Jason_InfinityRoofer said:

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Dr. Venkman said:

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It not cooling the house is all the proof you need that it was done incorrectly. Rule of thumb is 1 ton per 500 sq ft. so 2.5 tons on 2518 sq ft seems way off.

---

I have to respectfully Disagree. There is no "rule of thumb" in 2022 when dealing with Hvac. We have science. The fact that the AC wouldn't cool past 77 when it was over 100 degrees yesterday is actually a pretty good sign that his unit is sized correctly or not, who knows without a lot more info. . We have design temps, and 100 degrees is well outside of it. What is the Op design temp, should all be on the Man J.

If they arrived at 2.5 tons from a man j on a modern standard build house of 2500 sq ft, then we need to know what assumptions were made and where you are located. It won't fly in texas….anywhere.

---

I don't know. Sure, we have science for load calculations. But, at the end of the day, it really isn't an exact science when you take it down to the individual house like you're claiming it is. As AgAcGuy laid out, several assumptions are still made in these calculations. Anytime you make assumptions, you're opening up more room for error.

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You are correct. Absolutely.

I didnt mean to imply the calculation was the end all be all, I just know most AC contractors don't do it at all. ACGUY12 post has shown exactly why there is a value in having a true professional with experience and a HUMAN BEING thinking about it. This goes against my post to some degree, but I am in agreement with you. You have to use the science, and then understand the results and consequences. ACGUY got the same number, but he also understands the assumptions made that allowed that number to be produced. He then takes that number and relies on professional experience to temper and adjust to the right product. 50 years ago, they would have dropped at 5 ton in that house and it probably would have been a bit too big.

This is why you don't select the cheapest guy in town.

The other point he made cannot be overstated....what the builder and HVAC was SUPPOSED to do, and what they ACTUALLY did is not always the same. I know with roofing, I am inside attics a lot and I see all kinds of really bad stuff. Wires everywhere, insulation haphazardly tossed about, roof decking with holes in it that the original roofer just shingled over and didnt close.....all kinds of stuff.

Ive had similar issues with roofing in terms of 'how much do you need'. I can measure a roof all day long, but ultimately, I can look at it and say "Yeah, that number isn't right because of X, Y, and Z."

uncover&humpit said:

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Really appreciate the feedback. Our builder is supposed to come back with a solution by the end if this week. Hoping they will bite the bullet and replace the current unit with a 4 ton unit

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I would ask if you can upgrade to a two-stage system and put a 4 ton unit in.

I'd bet OP can, but not for free. It'll be an interesting read after the conversation happens and OP comes back.

Haha. Your reputation is intact. Good bull.

Our builder is going to replace the air conditioner, they want to install a 3.5 ton unit. Once I get the written offer, I am going to ask how much extra for a 2-stage 4-ton unit. They are having an entirely new mechanical contractor come out to do the swap. Guess they aren't too happy with the original installer. They mentioned that similar floor plans and layouts all had 3.5 ton or larger units.

That's great news IMO!

Loved to hear things are now going the correct way.
Professor Mech.Eng/Arch that also did work on the side in Aggieland
always began with 475sf/ton & 525sf/ton if a condition floor above it.
THEN
he ran calculations that included

• people loads, e.g. 20=1 ton (parties)
• windows
• shade trees
• volume
• heat generating fixtures &/or outlets
• insulation
• ventilation

So, if you got a 4ton single stage in those old days, with a lower SEER rating
he would have begun with 1900sf. So the improvements in insulation, SEER, CODE-enforced duct sealing, maybe you are A-OK?

This 1980's old house has more windows than normal, so 1776sf just got a variable stage 4 ton and we've never been so pampered since house was new.

You can always pay to consult with a Mech.Eng specializing in HVAC or more cheaply a Home Inspector pro .... call in show, free advice is The Money Pit

So the buulder came out last week and replaced the entire unit with a 3.5 ton unit. So far the new unit is able to keep up with the 100 degree temps never getting above the set temp of 75, the humidity in the house is lower and its running about 15 hours a day compared to 23 hours a day with the 2.5 ton unit. Im thankful Tilson saw their error and make a correction in a timely manner.