Homeowner question: Comparing cost vs efficiency
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  1. #1
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    Homeowner question: Comparing cost vs efficiency

    I hope it is ok to post this.. I'm not asking for pricing advice from anyone.. but for reference, I want to post some relative figures for what I'm looking at.

    Someone please tell me if this is not ok, and I'll pull this right away.

    Ok... First off... I'm not rich, so money is definetly an object. I currently have a 5-ton Goodman 10seer (Straight-A/C) unit manufactured in '99 I with a Bristol Scroll compressor. The compressor has a pin-hole in it on the side at an internal weld.

    New compressor installed - (**Edited: about twice the price of a 5-ton compressor)
    (I have no problem with this figure.. I know they don't give out free 5-ton compressors)

    Or I could get a new outside unit installed for about the same price and use the same evap coil/AH that is in place now, I'm guessing this would still put me somewhere in the 10 seer range.

    Or I could get a new 13 seer Heatpump inside/outside installed for roughly twice this. (I don't believe this has variable speed fan)

    Or.... I could go with a 16 seer unit with 2-stage compressor and variable speed fan for just a little more than 3x as much.

    I am in the deep south, the temps in the summer months are in the mid 90's and humidity runs very high. May-Aug are the big summer cooling months here. Winter's are relatively mild. I may have 1 month where the power bill gets up a bit in January, but nothing like the stretch we see in the Summer months. For heat it is just using the Internal coil heater, no air pump at this point. My summer cooling costs is prob $250-300 a month in the hottest months.

    I'm very confused on what to do here... the people I have talked with have all been straightforward, and I know it's probably impossible to determine what savings I would see from going with the higher seer units, but I'm just looking for an idea of how much more efficient would the higher priced units be over what I have installed now. I have to do something anyways.. with a hole in the compressor

  2. #2
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    If you edit out the price of the compressor, the post should be OK.

    I just read somewhere that replacing a 10 SEER system with a 13 SEER system would provide a 30% savings in operating costs. 14 SEER would be 40%, etc. I would take this as a ballpark estimate.

    If you replace the whole system, I would step up from the 13 SEER to the Goodman 14 SEER. Make sure you get the optional TXV (thermostatic expansion valve) for the air handler coil. It provides maximum cooling efficiency under all operating conditions.

    In my opinion, a 14 SEER offers the best combination of purchase price and true operating costs.

    A good installation is critical for a properly performing, long lasting system.

    Good luck.

  3. #3
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    Jul 2004
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    South Alabama
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    Done...
    I like the idea of the variable speed fan, I do have some issues with humidity in the house. It is 2400sq ft of living space with single pane windows. The tech recommended to stay with a 5-ton... he said that the variable fan would help with the humidity. It is a Carrier Infinity system BTW.
    But... that's a lot of money... One good point is I could get a low interest loan from the local power company, the other options I'm just going to have to put it on the Credit card which is not low interest.

    I hope I'm not being too much of a goober by asking these questions, but I've been reading these forums for a long time.

  4. #4
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    Quote Originally Posted by bmilam View Post
    Done...
    I like the idea of the variable speed fan, I do have some issues with humidity in the house. It is 2400sq ft of living space with single pane windows. The tech recommended to stay with a 5-ton... he said that the variable fan would help with the humidity. It is a Carrier Infinity system BTW.
    But... that's a lot of money... One good point is I could get a low interest loan from the local power company, the other options I'm just going to have to put it on the Credit card which is not low interest.

    I hope I'm not being too much of a goober by asking these questions, but I've been reading these forums for a long time.
    Goodman makes a variable speed air handler - the model# starts with AEPF. It can be used with any Goodman heat pump from 13 SEER to 18 SEER. Model# ARUF is the 3-speed air handler, ASPF is the 5-speed air handler.

    www.GoodmanMFG.com

    Carrier Infinity is the Cadillac of the line. Carrier also makes a mid-level Performance series which has excellent efficiencies when paired with the right air handler.

  5. #5
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    Hot and humid.
    A single stage with VS will make it feel better then what your old system did.
    A 2 stage with VS will be able to lower the humidity more yet. Possibily allowing you to set the stat a degree or 2 higher, and still feel as comfortable.

    Not sure how cold your area gets, or how long your heating season is. But a heat pump does help to lower the bill compared to strip heaters.
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  6. #6
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    Another thing I just thought about
    The tech said there wasn't any real reason to replace the evap coil.... (currently 10 seer) if I replaced the outside unit... I'm guessing it would be a 13 seer unit since thats the minimum. He explained that I certainly would not be seeing 13 seer.

    I understand that it would not be as efficient , but would I have anything close to my current 10 seer performance if doing this?

    I've been browsing/searching the forums for hours now... and have read some scary stuff now on mismatches. Should I be worried about this option?? Would it make sense to go ahead and replace the inside unit ?

    Sorry for the stupid homeowner querstions

  7. #7
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    If you reuse your old indoor coil. You could have anything from a 9 SEER to a 12 SEER.

    If your compressor fails, and the distributor or manufacturer ask for the mod and serial of the indoor coil, and it doesn't match, they will void the compressor warranty.

    Read the mismatch performance.
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  8. #8
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    Thanks Beenthere! That is a heck of a lot of difference.

  9. #9
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    Yep.

    And if they can't get it to work right in a lab. How is anyone gonna make it work right in the field.
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  10. #10
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    Your indoor humidity problems could be a result of an oversized system. 5 tons is a lot for 2400 sq. ft., but your climate might just warrant that. I have a smaller system (3.5 tons) for my house (around than 3500 sq. ft. including conditioned finished basement) and it cools to 72* on the hottest 90*+ days with fine humidity control; however, I am in Maryland, not Alabama. My home has shade, and yours may not. Insulation, windows, etc. also vary, so it's possible that you may need 5 tons (my point is to make sure! ). How often does (did) your system cycle on an average day? Oversized systems use more electricity. 2-stage systems help with humidity removal and longer cycles, but they still need to be sized properly. If any contractor wants your job, I would ask him to perform a load calculation to be sure of sizing.

  11. #11
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    Quote Originally Posted by beenthere View Post
    If you reuse your old indoor coil. You could have anything from a 9 SEER to a 12 SEER.

    If your compressor fails, and the distributor or manufacturer ask for the mod and serial of the indoor coil, and it doesn't match, they will void the compressor warranty.

    Read the mismatch performance.
    Why didn't they do a test with a 10 SEER outdoor unit and 13 SEER indoor unit mismatched? Don't they anticipate any problems with a setup like this? Interesting read nonetheless.

  12. #12
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    Quote Originally Posted by RyanHughes View Post
    Why didn't they do a test with a 10 SEER outdoor unit and 13 SEER indoor unit mismatched? Don't they anticipate any problems with a setup like this? Interesting read nonetheless.
    You can get the BTUs from the larger then needed coil.
    So all it would do is prove you lose latent BTUs with that match up.
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  13. #13
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    Quote Originally Posted by beenthere View Post
    You can get the BTUs from the larger then needed coil.
    So all it would do is prove you lose latent BTUs with that match up.
    Along with charge issues and efficiency issues, correct? I'm just checking because I thought even a 13 SEER mismatched coil on a 10 SEER heat pump was bad. I guess it's a gamble still.

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