HVAC DIY

Joined
May 16, 2011
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1,514
Location
Greenville, SC via Chicago, IL
My home has two HVAC systems, one per floor. My second-floor system is 22 years old. It's located in a spacious area of the attic. The returns and runs to vents are all flex duct. The current system still works. I feel that it's oversized as it cycles on for 5 minutes, then off for 20 during the summer months. I know AC compressor is 3-ton. The second floor is ~1250 sq ft. All brick home with quality thermal windows and R-19 insulation. Home is in Upstate South Carolina.

Armstrong Furance-G8A75DC10-18
Carrier coil-CE3AXA036000ABAA
Payne unit outside- PA12NA036-A

I've called a few contractors for quotes and they both have just sized the new replacement system based on the old set up. I KNOW this isn't correct, they're being lazy and not doing a manual S, and J. They will not get my money.

My thought:

Have someone help me properly size what I need. Purchase a simple Goodman single stage 80% furnace, 16+ seer setup based on my needs and assemble it next to existing. Remove existing and hire someone to do the sheet-metal work and connect line-set/compressor etc. Because everything is flex-duct, it's not challenging complete.

Whoever installed my current furnace takes zero pride in their work.

Anyone else tackle HVAC on their own?
 
If the unit doesn't run very long, downsizing the condensing unit for a smaller one, possibly 1 1/2-2 ton, while keeping all your existing furnace, coil, plenum, ductwork, etc. might be a less expensive alternative to replacing everything. I'm guessing you probably don't need the furnace in winter (since heat rises & you obviously have good insulation), so basically using your existing attic system as an air handler should get it done. A good friend of mine did this with his whole house system years ago-the A/C ran a lot, but it did an excellent job at dehumidifying the air & was less expensive to run than his old bigger condensing unit.
 
Definitely over sized. My whole house is 1200sqft and it has a 2 tonne unit that comes on for about 20 minutes and shuts off for an hour. In the summer when it's really hot 100F or more it will run for an hour and shut off for about 20 minutes.

The guy told me I could be fine with a 1 tonne but I insisted on a 2 tonne because we have no insulation in the walls of our 1940's house.

Get the contractor to do the actual J-Manual calculation and not just guess. Most are lazy and go by... "Well I just did a house this size" and the J-Manual calculation takes into account insulation, windows, levels, square footage etc.
 
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You can probably get the furnace and coil.
It is not legal for you to buy a condensing unit with the Freon in it, unless you are EPA certified.

At one time you could buy "dry" units. Not sure they are available anymore.

FYI, Goodman is now Chinese owned, if that matters to you.
 
The Braeburn 2200NC thermostat in my HVAC system can be adjusted to change the temperature increment from turning off to turning back on. Changing the increment from 0.5° to 2°, made the system run longer each time it turned on but it ran less frequently.
 
Put the job out for bid on service pro or thumbtack.

I used thumbtack for my ac/furnace replacement and found a very reasonable rate for a well installed American Standard system (Trane).

10 year warranty, no problems.

I looked at goodman but they had poor ratings, and I paid the same price for American Standard as someone else had quoted for goodman.

I believe I paid $2600 for a 2.5 Ton 14 seer American Standard unit with a 80 percent gas furnace installed.

Based on price of the materials, I figure the contractor made $800-$900 to install the unit and I was fine with that.
 
I calculated my own Schedule J. It was close tonnage wise to what's installed however, I keep my house at 78°F rather than the lower design point. This affects how long and how often the unit runs at. As someone else posted, my t-stat also could be tweaked to reduce the deltaT setting. I'll look into that.

Also designed my own duct system using Manual D and installed it myself. Previous system was restricted on both supply & return.

Still running a 27yr old 13 SEER Janitrol heat-pump. I clean the coils annually and closed up all return plenum leaks. House stays quite dry indoors given humid S. Tx conditions.
 
If it's got R22 in it, that stuff is crazy expensive now. You could get a HVAC company to remove that refrigerant and then sell it to them.
 
Originally Posted By: KJSmith
You can probably get the furnace and coil.
It is not legal for you to buy a condensing unit with the Freon in it, unless you are EPA certified.

At one time you could buy "dry" units. Not sure they are available anymore.

FYI, Goodman is now Chinese owned, if that matters to you.


Dry charge units are no longer available. They took advantage of a loophole in the R-22 phase out rules (charged with inert nitrogen at the factory instead of Freon). But they were generally the low end units as manufacturers weren't going to invest in high efficiency dry-charge units with regional standards on their way. The minimum efficiency required for new units in my region is 14 SEER.

Also, you are incorrect about Goodman. Daikin owns Goodman and is a JAPANESE company.
 
Originally Posted By: Schmoe
If it's got R22 in it, that stuff is crazy expensive now. You could get a HVAC company to remove that refrigerant and then sell it to them.


R-22 may be expensive, but with the sales dropping like a rock it's readily available and has actually come DOWN in price about 25% in the past six months. It's one of the commodities I manage for my employer. As long as leaks are repaired it's still way cheaper than replacing your system.

Current going rate if you're an OEM, is under $450 for a 30 lb jug. That's $15/lb. Many contractors are gouging.
 
Originally Posted By: flanso
The Braeburn 2200NC thermostat in my HVAC system can be adjusted to change the temperature increment from turning off to turning back on. Changing the increment from 0.5° to 2°, made the system run longer each time it turned on but it ran less frequently.


That would be the first thing that I would try. Find a thermostat that allows for greater temperature swings. They do exist. I think Lux makes one.
 
Originally Posted By: DBMaster
Also, you are incorrect about Goodman. Daikin owns Goodman and is a JAPANESE company.


OK, Goodman is Japanese owned, if that matters to you.
 
My Amana (Goodman) is 5 years old and we run the A/C cold like a freezer in the summer and the Furnace runs all the time in the winter because we have no insulation in the house and it's been rock solid reliable. Really happy with it.

I also keep the 24 volt ECM fan motor running 24 hours a day for circulation and to keep dust down. No issues.
 
Originally Posted By: KJSmith
Originally Posted By: DBMaster
Also, you are incorrect about Goodman. Daikin owns Goodman and is a JAPANESE company.


OK, Goodman is Japanese owned, if that matters to you.



Japanese knows how to make AC, Daikin is a very good brand in the Asian market.
 
Originally Posted By: PandaBear
Originally Posted By: KJSmith
Originally Posted By: DBMaster
Also, you are incorrect about Goodman. Daikin owns Goodman and is a JAPANESE company.


OK, Goodman is Japanese owned, if that matters to you.



Japanese knows how to make AC, Daikin is a very good brand in the Asian market.


I never said anything bad about them.
They are made in what I call far NW Houston.

Daiken moved all its USA manufacturing there earlier this year.... according to the local news.

Pretty sure Americans and Texans know a little about it also.
 
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They are not lazy. Maybe just pay someone for proper calcs instead. I cannot image more than $500 but may yield savings in equipment and energy costs latter.

I got lucky and had my home oil boiler downsized by 30% and notice the hot water savings over summer. As long as it keeps us warm the coldest day even on constant running(old one would cycle )
 
Japanese knows how to make AC, Daikin is a very good brand in the Asian market.

I never said anything bad about them.
They are made in what I call far NW Houston.

Daiken moved all its USA manufacturing there earlier this year.... according to the local news.

Pretty sure Americans and Texans know a little about it also.
Goodman used to be known only for their low cost and were typically sold to home builders. They had a bad reputation for quality, reliability, and longevity. This has changed dramatically since they were purchased by Daikin in 2012, and especially now that they started production in their new manufacturing facility in 2016.
 
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