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  1. #1
    Join Date
    Jul 2011
    Location
    New Orleans, LA
    Posts
    19

    Qusetion about Blower Motor, kWhrs etc.

    Forgive all the details. My question is pretty straightforward I think but the background may help. In another thread, I had mentioned that the blower motor on my ac had gone out several years in a row. The current motor is in its second season, so that wasn't the focus of the thread. In that thread, I was helped to find some big 'holes' in my return air chase which seemed to be pulling humid, hot attic air into the system. As soon as I plugged those, I could feel the difference.

    The other issue was my utility bill which was $300 for June with an average daily usage of about 107kwhs per day. What I noticed today looking back at prior year bills is that the average daily usage is up substantially this year. I don't think I'm talking about small differences:

    ...............2011.........2010
    June......108 kw...... 86 kw
    May.........78..................69
    April.........68..................43
    Mar..........47.................28

    I've been thinking that when I have some vacation time later this month, I want to get someone out to take a look at the system and at least do the annual maintenance. I'd like to ask them to check some other things out for me at the same time: look at duct design, possibly do a manual J calc etc.

    My thinking (correct me if I'm wrong) is that if they determine that I should have the duct work adjusted (need more air to back of house), I would want to make sure any changes to the ductwork I do now would be compatible with a new (possibly smaller) unit when I replace this one. I have 4 tons now which is probably on the big side and I've recently been doing some sealing, caulking etc. so my guess is that when this 12 yo unit goes, the next one will be sized smaller.

    1. I am now wondering if the increase in energy usage I am seeing could be related to an impending problem with the blower motor, especially considering that up until recently, it was probably pulling pretty filthy air into the system from the attic.

    2. If an issue with the blower motor is likely, what should I ask them to look for? (Remember, for several years, 'they' just came out and replaced it to the tune of several hundred dollars...no word about root causes of failure.

    3. Out of sheer curiosity, how does the total energy usage of a central unit break out between the components. In general, for a well installed say 4 ton unit, how much of the average 4800kw per hour are eaten up by the compressor? The blower? etc?

    Like I said, I will be scheduling someone to come out later in Aug or early Sept and I'd like to be able to have some understanding so I know what to ask while he's here etc.

    Thanks

  2. #2
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    Quote Originally Posted by Nola_Gal View Post
    ...1. I am now wondering if the increase in energy usage I am seeing could be related to an impending problem with the blower motor, especially considering that up until recently, it was probably pulling pretty filthy air into the system from the attic. The indoor fan uses about 20% of your system power when cooling in the recommended auto setting on your stat.

    2. If an issue with the blower motor is likely, what should I ask them to look for? (Remember, for several years, 'they' just came out and replaced it to the tune of several hundred dollars...no word about root causes of failure. Who knows? Your history is not good.

    3. Out of sheer curiosity, how does the total energy usage of a central unit break out between the components. In general, for a well installed say 4 ton unit, how much of the average 4800kw per hour are eaten up by the compressor? 80% The blower? 20% etc?...
    Your power consumption has changed for some other reason. A 10% to 15% increase in blower power consumption (or 2% to 3% increase in total power consumption due to the blower motor) would probably overheat the blower motor and cause it to shut off on safety. It could be a defective compressor run capacitor or increased running time due to dirty indoor coil, filter, shortage of refrigerant, dirty outdoor coil, some other factor or a combination of factors.
    That is a pro's job. Good luck.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  3. #3
    Join Date
    Jul 2011
    Location
    New Orleans, LA
    Posts
    19
    Are doing/checking all of those things generally considered 'standard' when getting annual maintenance?

    Don't worry. I'll caulk and even re-seal loose ducts, but I have no illusions about doing anything beyond that myself. I went on Angie's list today and found a local AC company with good reviews. I'll be calling them tomorrow to get something scheduled.

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