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  1. #1
    Richard Thacker's Avatar
    Richard Thacker Guest

    Default Air Conditioning, Ambient Temperature and RLA Effect

    Gentlemen I have a question that I would like explained, if possible, by someone with some knowledge of motors.This occurred last year...

    Example: 3.5 ton system / with a listed R.L.A. of 18.4 Amps / Outdoor temp is 91*F / Return air is 74*F / Supply air 58*F / Actual observed R.L.A 18.1amps / unit is 2 years old

    I called for the system to be further evaluated by an HVAC Specialist because the RLA seemed to running to high and may be a sign of motor concern. The answer I recieved from the contractor who installed the unit was " The system is running normal and there is not a problem with amp draw. The higher amp draw is due to very high outdoor temperatures making the unit have to work harder."

    Now I don't know a lot about motors, but I can not see how a system that under normal conditions would be running +/- 11.5 amps would need that much more power for a day that was only 91*F. What I would like to know, and explain it in simple terms:

    1. Is the HVAC contractor correct?
    2. If he is correct when did 91*F become "very high outdoor temperatures" and why would it cause such a high jump in the RLA?

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  2. #2
    Join Date
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    Default Re: Air Conditioning, Ambient Temperature and RLA Effect

    Perhaps you have an HVAC background, but IMO that's well beyond the every HI SOP I'm aware of, and likely to land you in hot water.

    Last edited by Michael Thomas; 03-09-2009 at 08:01 AM.
    Michael Thomas
    Paragon Property Services Inc., Chicago IL
    http://paragoninspects.com

  3. #3
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    Default Re: Air Conditioning, Ambient Temperature and RLA Effect

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  4. #4
    A.D. Miller's Avatar
    A.D. Miller Guest

    Default Re: Air Conditioning, Ambient Temperature and RLA Effect

    Quote Originally Posted by Jerry Peck View Post
    JP: I just read that thread and now can safely report to you that I know less about the matter than before.


  5. #5
    Richard Thacker's Avatar
    Richard Thacker Guest

    Default Re: Air Conditioning, Ambient Temperature and RLA Effect

    Jerry, thank you. That did explain a great deal...I think.


  6. #6
    Denny L West's Avatar
    Denny L West Guest

    Default Re: Air Conditioning, Ambient Temperature and RLA Effect

    Did you get that answer in writting from the contractor . cause that will defuinatly clear you on that . and If Your Not Lisc. HAVC that is out of the scope of a home inspection. sometimes its better to say its not my area of expertise and recommend a HAVC contractor to evaluate then its up to the client to except or not .


  7. #7
    Richard Thacker's Avatar
    Richard Thacker Guest

    Default Re: Air Conditioning, Ambient Temperature and RLA Effect

    Gentlemen I have a question that I would like explained, if possible, by someone with some knowledge of motors.This occurred last year...

    Example: 3.5 ton system / with a listed R.L.A. of 18.4 Amps / Outdoor temp is 91*F / Return air is 74*F / Supply air 58*F / Actual observed R.L.A 18.1amps / unit is 2 years old

    Correction: The actual supply Temp at the time was 68*F


    I Don't know if data would have made a difference, but is still a concern on its own merits.


  8. #8
    Richard Stanley's Avatar
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    Default Re: Air Conditioning, Ambient Temperature and RLA Effect

    only 6 degree delta -- needs service.


  9. #9
    Richard Thacker's Avatar
    Richard Thacker Guest

    Default Re: Air Conditioning, Ambient Temperature and RLA Effect

    So as I see it RLA only becomes relevant when it exceeds the manufacturers listed maximum limit and amp draw should not be used as a standard for measuring a motors condition.


  10. #10
    Join Date
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    Default Re: Air Conditioning, Ambient Temperature and RLA Effect

    Quote Originally Posted by Richard Thacker View Post
    So as I see it RLA only becomes relevant when it exceeds the manufacturers listed maximum limit and amp draw should not be used as a standard for measuring a motors condition.
    That's a good way to put it.

    Now, for a knowledgeable HVAC guy who is also checking many other things and putting them all together to arrive at some 'Yep, it's about a goner' or 'Nah, it's okay for now' decision, that's way beyond my knowledge with air conditioning.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

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