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: 616

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

Christopher Talarico posted a discussion

Heating with Tankless Water Heater & Hydronic Air Handler vs. Gas Furnace

Hi,I've looked around online and haven't found a lot of good information on home heating with…See More
8 hours ago
Profile IconSara Sabol, Christopher Talarico and Aaren Stewart joined Home Energy Pros
10 hours ago
Hal Skinner replied to Andy Gostisha's discussion Disguising Ductless Heat Pump Units
"Hi Andy. The bare metal units on a roof stick out like a sore thumb .  Coating them with our…"
10 hours ago
Paul Morin replied to Stephen Standley's discussion Which reading is more reliable on a Minneapolis Duct Blaster?
"Sorry for chiming in so late.  Sean’s comment early on in the discussion was the closest…"
14 hours ago
jerry gentile posted a status
"hello- anyone challenge the written QCI exam?"
16 hours ago
Kevin Jordan posted photos
21 hours ago
Susan E. Buchan's event was featured

EEBA Excellence in Building Conference at Doubletree Union Station Hotel

September 23, 2014 at 8am to September 25, 2014 at 2pm
yesterday
Susan E. Buchan posted an event

EEBA Excellence in Building Conference at Doubletree Union Station Hotel

September 23, 2014 at 8am to September 25, 2014 at 2pm
yesterday

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service