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  1. #1
    Join Date
    Sep 2008
    Posts
    18

    Ductless split system

    My contractor replaced a 9000 BTU 10 SEER ductless system with a 20 SEER Inverter system rated 3000-12000 BTU. We are in the tropics, air temperature in the high 80's mostly, year round. I keep accurate records of power consumption and temperatures, and the new system uses about 70% as much power as the old, not half as advertised.

    Old unit used 6 KW per day, new one about 4.3KW per day. At our very expensive power rates it adds up. Is this as would be expected, or might something not be working right. He already evacuated the system to humor me and weighed the charge to make sure it had come charged properly, and it had. It cools great and is quiet, just not as efficient as we had hoped. He had sold me on it using a chart from the manufacturer that claimed a 20 SEER would use 1/2 the power of a 10 SEER.

    Thank you!

  2. #2
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,570
    the new unit is 30% larger than the old unit.
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

  3. #3
    Join Date
    May 2009
    Location
    West L.a
    Posts
    93

  4. #4
    Join Date
    Sep 2008
    Posts
    18

    Ductless split

    Quote Originally Posted by Freezeking2000 View Post
    the new unit is 30% larger than the old unit.
    For what it is worth, the temperature and humidity in the room is the same as with the old unit and the manufacturers chart shows it will perform at 20 SEER and replace anything from 3000 BTU up. It only runs at full speed for the first few minutes when turned on, and then the inverter slows the compressor down until it is barely running. Are they being misleading?

  5. #5
    Join Date
    Oct 2009
    Location
    San Diego, CA
    Posts
    55
    Keep in mind that with your new variable system which is constantly running, duct losses are a much bigger factor and can cause you to lose a lot more "cold" if they are leaky and/or poorly insulated. That's the price to pay for additional comfort. If your ducts are easily accessible, have them checked for leaks and insulation (that should have been evaluated when the new system was installed).

    I'm surprised that the humidity is the same as with the old system - the new one should be running more and thus removing more humidity which should let you bump the thermostat up a couple degrees and maintain the same comfort.

  6. #6
    Join Date
    Sep 2008
    Posts
    18

    Ductless split

    It's ductless.

    The compressor runs more hours, but the discharge air isn't quite as cold due to the lower pressure from the low speed of the compressor. The indoor unit slows down too but the delta across the indoor unit is not as great after the room stabilizes at temperature. Humidity averages out and the temperature is more consistent in the room. I have several more units to replace and they would pay for themselves pretty quickly at our electric rate if they actually work as advertised

  7. #7
    Join Date
    Oct 2009
    Location
    San Diego, CA
    Posts
    55
    Quote Originally Posted by jimblu View Post
    It's ductless.
    Whoops - totally forgot that bit. The unit must be less efficient when running at less than full capacity, then.

  8. #8
    Join Date
    Sep 2005
    Location
    Bay Area, CA
    Posts
    843
    It being oversized marginally shouldnt be an issue unless the previous unit was undersized, as its an inverter. Temp outside vs kw used is only telling you part of the story though.
    Global Warming or: None like it hot
    No pleasure, no rapture, no exquisite sin greater... than central air. -Dogma

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,754
    How do you know its using 70% as much as the old unit.
    Was the old unit on its own electrical meter?
    Is the new unit on the same seperate electrical meter?

    If no to both of those questions. How do you know that its using 70% of what the old unit did?

    If your electric bill with the old unit was 100 dollars a month. And now with the new unit, its 75 dollars a month. That could be a 50% reduction in electric for A/C.
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    How many times must one fix something before it is fixed?

  10. #10
    Join Date
    Sep 2008
    Posts
    18

    Ductless split

    I have a digital KW totalizer on the circuit, along with a recording thermometer and humidity. The outdoor temp, humidity, sunshine and wind is pretty consistent. I could see the difference on the day it was installed and have a few months history to look at now. I guess my question is if you replace a 10 SEER with a 20, in real life is the bill likely to be cut in half?

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