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: 393

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

angela hines replied to Alan Gindt's discussion Minneapolis Blower Door, Pressure Pan, and Bacharach CO 3 For Sale in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"What is the price for them together? What is the price just for the blower door set?"
16 hours ago
Alan Gindt replied to Alan Gindt's discussion Minneapolis Blower Door, Pressure Pan, and Bacharach CO 3 For Sale in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Yes"
16 hours ago
Profile IconKevin Love, Shannon Kahl and Lauren McNutt joined Home Energy Pros
17 hours ago
Anna Jursik's blog post was featured
18 hours ago
Everblue posted a status
"New Energy Auditor Jobs posted on our Massachusetts Job Board! Check them out: http://www.everblue.edu/hiring/job-board/massachusetts"
19 hours ago
Everblue posted events
20 hours ago
angela hines replied to Brooke Ingram's discussion 3 full sets of testing equipment available for sale! in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Hi is the Minneapolis blower door set still available?"
21 hours ago
angela hines replied to David Allen's discussion Like new! Great Deal! Minneapolis Blower Door system, Duct Blaster and Flir i-7 Infrared Camera for sale in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"I am interested in the blower door and camera. Are they still available? If so i will buy. Please…"
21 hours ago
angela hines replied to Alan Gindt's discussion Minneapolis Blower Door, Pressure Pan, and Bacharach CO 3 For Sale in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Is this still for sale? I am interested and would want to buy."
21 hours ago
angela hines joined allen p tanner's group
Thumbnail

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More
21 hours ago
Anna Jursik posted a blog post
21 hours ago
Tom Mallard replied to Kaushal Bharath Raju's discussion Affordability & Deep Energy Upgrade/Passive House Retrofit in Berkeley, California.
"After seeing the cost estimates by Glenn, my addition of insulation board under the siding on a…"
yesterday

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service