Comments on: 5 Tips for Sizing an Air Conditioner

By: Ben graf

Ben graf — Mon, 12 Feb 2024 16:52:02 +0000

I am only a homeowner so I don’t know what am hvac contractor would, but the carrier infinity I own (2018 gas furnace and heat pump AC) has a range of cfm, and that range was defined when the size of the AC was put into the computer. Even with the best energy settings I had too many registers for the cfm the blower would produce and the airflow out each register was so low in two bedrooms that they wouldn’t cool. Sizing up the AC seemed to fix the problem as then the cfm increased. Sorry I can’t be more helpful

By: Dustin Cole

Dustin Cole — Sun, 11 Feb 2024 18:28:34 +0000

In reply to Ben graf. Interesting, can you share your match-up models? And what your design vs actual cfm output was?

By: Ben graf

Ben graf — Wed, 07 Feb 2024 18:06:24 +0000

I have a carrier infinity furnace and heat pump/AC. We sized it for minimal cooling loads only to find out that determined max airflow by the infinity variable blower. Had I go up a ton in size to get enough airflow to cool bedrooms.

By: JC Garcia

JC Garcia — Mon, 07 Aug 2023 15:55:39 +0000

Nice article, but as a licensed HVAC contractor myself, it pains me to hear your perception and experience with contractors. It is our job to perform load calculations for all installations and ensure maximum efficiency and durability. If you run into a company that does not live up to this standard of quality, then you aren’t getting the value you are being promised.

On a second note, your system is only as good as it’s weakest link. Undersized ducts combined with oversized systems make for a tragically inefficient and uncomfortable system. Very little attention is paid to duct sizing, and that requires additional calculating by the contractor. Visual inspections inform you of any leakage, poor insulation, and overall poor design issues.

I agree wholeheartedly that the consumer should be as well informed as possible. This allows for a more productive conversation with the contractor, leading to a greater level of overall satisfaction and pride of ownership.

By: John

John — Sat, 01 Jul 2023 15:51:02 +0000

I recently got quotes for a new Carrier Infinity natural gas furnace and heat pump for a house in Minnesota. The furnace has a DC variable speed blower and modulated gas capability. One of the salesman stated that they use a computer program that imports previous energy usage data from the utility companies to determine the size unit needed. He stated that Model J heat load calculations were not needed. Just wondering if anyone has any thoughts on the use of this type of program? Thanks.

By: Travis Jones

Travis Jones — Thu, 29 Jun 2023 02:19:24 +0000

In reply to Travis Jones. Didn't realize this comment hadn't been approved when I posted the comment below. :-)

By: Travis Jones

Travis Jones — Wed, 28 Jun 2023 11:45:40 +0000

Allison – Enjoyed chatting at your book event in Austin in May!
(Thought I posted this question the other day … so if I posted it on another blog, sorry for the repetition.)

This post gets to one of my key questions. I’m in roofing and solar and am learning the home performance side of things. Bought a blower door and am learning to use it.

My question is about a rule of thumb or set of guidelines for helping homeowners understand the appropriateness of their current level of cooling. I’m in Dallas, and we oversize EVERYTHING! 🙂

What inputs would you need to give a reasonable response?

My thought is
1. Size of the home
2. Year the home was built
3. Tons of AC

Let’s use my home.
1. 2,535
2. 1966
3. 7 tons (2 ton and 2.5 ton for downstairs. 2.5 ton for upstairs)

At 1 ton per 362 square feet, that can’t be great. I think I’m oversized at my current level of air sealing. Once I run my blower door test and have that number (I’m betting north of 20), I can come up with a reasonable target.

Without more info though, could you say something like … “A house that age and size should be at 500 sqft/ton … or 700 sqft/ton … or ???

Appreciate any and all input.

Best,
Travis Jones

By: Travis Jones

Travis Jones — Tue, 27 Jun 2023 00:46:58 +0000

Do you have any rules of thumb for tons per square foot?

I would love to ask a customer 3 questions:
1. How many square feet is your house?
2. What year was it built?
3. How many tons of AC do you have?

If they say … 2,500, 1968, 7 tons … I could say … with proper air sealing and with some added equipment (especially dehumidification), we could get you down to … 4 tons?

BTW — that’s my house. And I live in Dallas. 🙂

By: Galen

Galen — Thu, 22 Jun 2023 02:15:07 +0000

In reply to BDF. Probably a setting on the setup to adjust fan speed. Mine has two" "normal" and "quiet" Quiet seems to be on fan speed lower than Normal

By: KasperG

KasperG — Wed, 21 Jun 2023 20:33:37 +0000

Thank you for the interesting article, topics that has always interested me. I do EnerGuide evaluations for homes in Ontario and right now we’re recommending heat pumps for home owners looking to ungrade their heating system and electrify. As we are heating dominant here, the cooling loads tend to be smaller than the heating loads in a typical home, when a homeowner installs a heat pump sized to heat their home, naturally it results in an oversized ‘AC’. We also recommend variable capacity units but as stated in the article this doesn’t fully solve the issue. On top of issues with humidity levels are there other unforseen consequences of this type of upgrade?