Replaced my A/C this weekend, results of downsizing by 1/3.

Recently my 13 yr old Carrier A/C devolved a leak and I chose to replace the system rather than track down the leak and repair the coil. I had been reading about doing manual J calculations and how contractors are scared to death to undersize. I had been talking to co-workers about this and it's an uphill battle getting them to think different than 1 ton per 500sq ft. So I decided to take confidence in correct sizing and "put my money where my mouth is" and install a 2 ton sized A/C.

House: 1587sq ft located in Oklahoma City, built 1999.
OLD A/C: Carrier 3 ton 12SEER system original to the house.
New Condenser: Thermalzone (Rebadged Rheem/Ruud) 2 ton 14.5 SEER.
New coil: 2 ton RFCL 13-16SEER with TXV

Results:
Temperature the old unit cycled until it was above 105, clearly oversized for our area. New 2 ton unit can keep 76F inside with a 100 degree outdoor temperature, but runs continuously to do so.
Humidity is HIGHER in the day with the new system even though it runs more. 45% vs. 40% for the old system. I've already reduced the 3 ton blower to it's lowest speed.
As a test I've captured the condensate in a bucket to measure humidity removal. The 3 ton system with piston metering pulled more humidity by day, less by night. The new TXV system pulls more humidity at night than day. Both units keep humidity about 45% at night.
Power Old unit consumed 3,000 to 3,500 watts depending on outside temperature. New unit consumes 1,800 to 2,500watts depending on outdoor temperature. Power use is on my in home wattmeter and includes blower consumption.
Delta T Old unit got about 18 degrees most of the time, day or night. New unit gets 14 degrees in day, 18 degrees at night. Keep in mind the blower speed was lowered when the new A/C was installed.
Cycle time Cycles were running about 6 minutes with the old unit, new unit runs about 8-10 minutes per cycle.
Noise New unit is WAY quieter, both units have 8 pole motors. Scroll compressor can barely be heard compared to the recip compressor of the old unit. With the new unit you can barely hear the fan, very impressed. Neighbor still has his 3 ton builder unit with the 1125 RPM fan and it's twice as loud as my old unit.

The coworker that helped me install it was impressed with how quiet the unit is and how much cooling it put out considering that it's only a 2 ton. He was a bit skeptical that the 2 ton could pull it off, but it's doing so with flying colors IMHO. So, believe the load calculations and don't fudge the input number to get the result you want. Yes the numbers may seem low, but they DO work !!!

Views: 1570

Comment

You need to be a member of Home Energy Pros Forum to add comments!

Join Home Energy Pros Forum

Comment by Tom DelConte on December 10, 2013 at 11:09am

Nicely done Install !

Comment by Curt Kinder on September 9, 2012 at 12:41pm

Absolutely agree - we routinely drop tonnage by 0.5 to 1.0 following a careful Man J, generally including a Blower Door test to nail down infiltration figure

Forum Discussions

How would you insulate this roof?

Started by David Butler in General Forum. Last reply by John Hatfield 2 hours ago. 3 Replies

Psychrometric Chart Training

Started by John Krochmalny in Training 23 hours ago. 0 Replies

Dirty solar panels

Started by Evan Mills in General Forum. Last reply by Stacie Bagnasco on Monday. 1 Reply

Latest Activity

Crista replied to Brad Cook's discussion Too many Heat Pump Water Heaters in a basement?
"You might find this study of…"
1 hour ago
Profile IconCrista, David Potter, Walter Neboshynsky and 3 more joined Home Energy Pros Forum
1 hour ago
Lindsay Bachman's event was featured
Thumbnail

2017 HPC California Regional Home Performance Conference & Trade Show at Hilton Long Beach

November 14, 2017 at 7am to November 15, 2017 at 3pm
We are excited to join together with industry leaders along with fellow weatherization…See More
1 hour ago
Joe Hughes's event was featured
Thumbnail

HEALTHY BUILDINGS SUMMIT 2017 Conference at Seven Springs Mountain Resort

November 2, 2017 to November 4, 2017
Join us for another year of outstanding "Research to Practice" presentations with world class…See More
1 hour ago
Michael Duclos's event was featured
Thumbnail

Passive House Massachusetts - Symposium at District Hall, Boston, MA

October 25, 2017 all day
Getting High Performance Buildings DonePassive house standards and strategies have come a long way…See More
1 hour ago
Diane Chojnowski's event was featured
Thumbnail

2017 Home Performance Coalition California Regional Home Performance Conference & Trade Show at Hilton Long Beach

November 14, 2017 to November 15, 2017
We are excited to join together with industry leaders along with fellow weatherization…See More
1 hour ago
John Hatfield replied to David Butler's discussion How would you insulate this roof?
"The solution maybe installation of foam fill panels between the existing raised metal ribs within…"
2 hours ago
Marc Tannenbaum posted a blog post

3 Issues HVAC contractors Should Know About Impacting Customer Comfort and Health

There is an epidemic of people suffering in many of the 100 million homes across the U.S.  Many of…See More
2 hours ago

Photos

Loading…
  • Add Photos
  • View All

© 2017   Created by Home Performance Coalition (HPC)   Powered by

Badges  |  Report an Issue  |  Terms of Service