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: 824

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

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.

Latest Activity

Bradford E. White replied to Elizabeth Guinn's discussion ERV in need of backflow preventer.
"I would use an in-line backdraft damper such as Artis Industries or the ones made by Fantech and…"
13 hours ago
Kim Tanner posted a video

Wireless Air Leakage Testing

This webinar will discuss the use of WiFi technology to conduct and document blower door and duct leakage tests for compliance with local energy codes. The s...
14 hours ago
Profile IconPerry Grossman, Daniel Pate and Ottawa Furnace Filters joined Home Energy Pros
14 hours ago
Kirsten Richnavsky added a discussion to the group Building Performance Institute (BPI)
Thumbnail

Breaking the link between unhealthy homes and unhealthy kids

Listen in on IAQ Radio to a discussion on reducing the household triggers that cause asthmaattacks…See More
16 hours ago
Kirsten Richnavsky posted a discussion

Breaking the link between unhealthy homes and unhealthy kids

Listen in on IAQ Radio to a discussion on reducing the household triggers that cause asthmaattacks…See More
16 hours ago
Kim Tanner posted events
17 hours ago
Ottawa Furnace Filters posted a blog post

Some Useful Information about Furnace Air Filters

There is not much we can do about the air pollution outside of a house in Ottawa, Canada, but we…See More
18 hours ago
Fresh Air Duct Cleaning posted blog posts
22 hours ago

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service