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  1. #1

    Trane air conditioner: 13 versus 15 SEER?

    Our 15 year old Carrier AC has failed yet again and I'm not going to fix it this time. We've gotten a few quotes and I've zeroed in on one from a small reputable dealer who sells Trane.

    The choice I have to make is between the XB13 "standard efficiency" 13 SEER unit and the XR15 "high efficiency" 15 SEER unit. Both are four ton with single stage compressors. We're replacing both the compressor and the coil.

    We're in Southern California so the AC typically gets used on and off during the summer and that's it. However, our electric rates are pretty high. The 15 SEER unit is 25% more expensive than the 13 SEER unit and the actual dollar amount isn't trivial. I'm thinking it's not worth it based on the payback. However, I'd very much like to get some feedback on that. It's also worth keeping in mind that our old Carrier was probably 10 SEER or less.

    Thanks!

  2. #2
    Well the 15 SEER mathematically should use about 13% less energy than the 13 SEER, so depending on what % of your electricity bill your A/C is that may or may not be a substantial difference for you.

    Also consider that with Trane the XR units have a better warranty than the XB unit. XR has 10 years on the entire condenser whereas the XB Unit has 10 years on the compressor and 5 years on everything else (If you register it that is). Check the Trane website for more info on that.

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,234
    Remember that few "15 SEER" units will get 15 SEER without a matched high efficiency blower motor inside. The XR15 is certainly one of them. You'll get 14 SEER which can save you a few bucks over 13.

    The XR gives you a bit nicer unit than the XB13, namely some sound deading effords. The XB300 is a whole nuther story!

  4. #4
    Thanks for the feedback. I'll be keeping the current blower (and of course all the existing piping). Then again, I probably won't get 13 SEER out of the XB13 either. The warranty is longer on the XR15 but at 25% more cost I still don't think it's worth it.

    The XB13 is a bit nosier but nothing we can't handle. I expect it'll be quieter than the Carrier was.

    If there is nothing inherently bad with the XB13 unit I think I'll go that route.

    Thanks again!

  5. #5
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,311
    Keep in mind an A/C unit has to run 7 minutes before it gets it's maximum efficiency. Oversized units with cycle off before you ever get past the first 7mins. Undersized units will get past the first 7 minutes a lot more often, but you risk it being a few degrees hotter in your house for a few hours on the days that exceed design conditions. When doing your manual J you could reduce the outside and/or increase the inside design temperature a trade off for lower power bills. If you're OK with 80 inside when it's 100 outside you can put in a smaller unit (that uses less power) than if you require 70 when it's 100 outside.

  6. #6
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,234
    You will get 13.00 from an XB13 and matching coil. Just when you try to get much higher than 14, it takes the efficient fan motor to do it.

  7. #7
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,669
    if the furnace is 15 years old i would replace it also ,get a furnace with a ecm motor. especialy if electric is high

  8. #8
    I can't think of any time the AC has run for less than seven minutes. When it's hot, it runs in something more like half hour cycles. For reference, hot here is 80's to low 90's in the extreme (we're on the coast). Correct me if I'm wrong but with both units being four ton (I couldn't find detailed specs like BTU's) they'll have the same cooling capacity, right?

    The furnace is 15 years old but it works fine and I'm just not prepared to spend the money to replace it for the sake of increased efficiency. The payback period is just too long to justify it.

    I'd say we run our AC for something like 30-60 total days a year. The furnace is used sparingly as well, maybe running for a few hours in the morning and a few more at night. The weather tends to be pretty mild here in San Diego.

    Thanks again and if you have more info to share please do!

  9. #9
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,311
    4ton with a 90 degree design temp is either a really big or very poorly insulated house.

  10. #10
    The house is 2,700 square feet (two floors) with a concrete tile roof and stucco exterior. The insulation is average.

  11. #11
    Join Date
    Apr 2008
    Location
    Northwest Arkansas via Chicago Area via Straight Up from There on Lake Superior
    Posts
    1,411
    Quote Originally Posted by OpenTrackRacer View Post
    The house is 2,700 square feet (two floors) with a concrete tile roof and stucco exterior. The insulation is average.
    Not a pro, but I would consider more attic insulation and some caulking. We're at high 90's now in NW AR and my 4 ton dual fuel HP on an ~3700 sqft house with temp at 78 seems only to go into 2nd stage when it runs long in low stage and the timer kicks it up. Typically, I have a hard time getting the AC to run longer than 5-7 minutes. Sounds like my unit is over sized for cooling to me but no 3.5 ton unit was available and I guess 3 ton was too small.

  12. #12
    I'm not sure what you're getting at. I'm not upgrading to a larger AC unit or dissatisfied with the cooling ability of my current Carrier (when it worked). I'm simply replacing a defective air conditioner with a new one of the same cooling capacity.

    Incidentally, when I run my AC the thermostat is usually set for something more like 72-74.

    Quote Originally Posted by jerryd_2008 View Post
    Not a pro, but I would consider more attic insulation and some caulking. We're at high 90's now in NW AR and my 4 ton dual fuel HP on an ~3700 sqft house with temp at 78 seems only to go into 2nd stage when it runs long in low stage and the timer kicks it up. Typically, I have a hard time getting the AC to run longer than 5-7 minutes. Sounds like my unit is over sized for cooling to me but no 3.5 ton unit was available and I guess 3 ton was too small.

  13. #13
    Join Date
    Apr 2008
    Location
    Northwest Arkansas via Chicago Area via Straight Up from There on Lake Superior
    Posts
    1,411

    Talking

    Referring to a previous post with which I agree: "4ton with a 90 degree design temp is either a really big or very poorly insulated house". When ever you replace HVAC you should reassess whether you can put in the "right" equipment. Pre-existing size does not mean correct size. You also said hat your electric is high. Well, one way to decrease it is to replace over sized equipment and to improve insulation.

    My previous unit was the same size as the new and it appears over sized after some insulation upgrades and more efficient system. Just trying to be helpful.

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