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: 1531

Comment

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

Join Home Energy Pros

Comment by Tom DelConte on December 10, 2013 at 8:09am

Nicely done Install !

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

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

Videos

  • Add Videos
  • View All

Latest Activity

Profile IconJeffery Liang and Ellen Phillips Soroka joined Home Energy Pros
yesterday
Charles Cormany added a discussion to the group Job Board
Thumbnail

Energy Efficiency Incentive Program Manager - Efficiency First California (Berkeley)

Position Title: Program Manager Terms: Full time, available immediatelyAbout Efficiency First…See More
Thursday
Charles Cormany joined Diane Chojnowski's group
Thumbnail

Job Board

This group is for posting jobs related to all aspects of the home performance industry including…See More
Thursday
Linda Wigington liked Home Energy Magazine's blog post Art Rosenfeld's Legacy
Thursday
terry nordbye added a discussion to the group Energy Auditing Equipment for Sale, Trade or to Purchase
Thumbnail

Combustion anaylizer Testo 310

This little beauty only has a few hours on it. Almost brand new in box.Sell: $350.Terry 415 669…See More
Thursday
Barbara Smith's video was featured

Indiana HCA...On Location - Celebrating 40 Years of the Weatherization Assistance Program (WAP)

The Indiana Housing and Community Development Authority (IHCDA) interviewed two clients of Weatherization Assistance Program (WAP). Both homes were weatheriz...
Thursday
Home Energy Magazine's blog post was featured
Wednesday
Profile IconEfficiency First California and Kevin Daly joined Home Energy Pros
Wednesday

Home Energy Pros

Welcome to Home Energy Pros – the unique digital community by and for those who work in the home energy performance arena.

Home Energy Pros was founded by the developers of Home Energy Saver Pro (supported by the U.S. Department of Energy) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network. Please honor our Guidelines

© 2017   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service