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  1. #1
    Join Date
    Dec 2008
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    103

    Question Approximately how much electricity in watts is my Heat pump using?

    outdoor unit: 2 ton XL16i
    air handler: Train 4TEE3F31B1000AA

    How many watts does it use in stage 1 after it's reached full speed?
    Stage 2?
    aux heat?

    Just trying to figure out how much the thing costs to run for an hour.

  2. #2
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
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    3,304
    Quote Originally Posted by Ziocarl View Post
    outdoor unit: 2 ton XL16i
    air handler: Train 4TEE3F31B1000AA

    How many watts does it use in stage 1 after it's reached full speed?
    Stage 2?
    aux heat?

    Just trying to figure out how much the thing costs to run for an hour.
    From Trane document titled "Split System Heat Pump Product & Performance Data", page 7.


    COOLING SENSIBLE HEATING
    COIL CFM CAPACITY CAPACITY KW SEER EER CAPACITY KW HSPF COP
    4TEE3F31A1 780 22800 16900 1.92 16.00 11.9 20000 1.54 8.4 3.8

    Page 31 says for 1st stage:
    4TWX6024B1 WITH 4TEE3F31A1 AT 600 CFM 1ST STAGE
    O.D. HEATING CAPACITY MBH AT TOTAL POWER IN KILOWATTS AT
    TEMP. INDOOR DRY BULB TEMP. INDOOR DRY BULB TEMP.
    F. 70 75 80 70 75 80
    2 5.2 5.2 5.1 1.22 1.26 1.29
    7 6.5 6.4 6.3 1.23 1.26 1.30
    12 7.7 7.6 7.6 1.24 1.27 1.31
    17 9.0 8.9 8.8 1.24 1.28 1.32
    22 9.7 9.6 9.5 1.25 1.29 1.33
    27 10.4 10.3 10.2 1.26 1.29 1.33
    32 11.2 11.0 10.9 1.26 1.30 1.34
    37 12.4 12.3 12.2 1.27 1.31 1.35
    42 14.5 14.3 14.2 1.28 1.32 1.36
    47 16.5 16.3 16.2 1.29 1.33 1.37
    52 17.7 17.6 17.4 1.30 1.34 1.38
    57 19.0 18.8 18.6 1.31 1.35 1.39
    62 20.3 20.1 19.9 1.32 1.36 1.40
    67 21.5 21.3 21.1 1.32 1.36 1.40
    72 22.8 22.5 22.3 1.33 1.37 1.41

    Page 31 says for 2nd stage:
    4TWX6024B1 WITH 4TEE3F31A1 AT 800 CFM 2ND STAGE
    O.D. HEATING CAPACITY MBH AT TOTAL POWER IN KILOWATTS AT
    TEMP. INDOOR DRY BULB TEMP. INDOOR DRY BULB TEMP.
    F. 70 75 80 70 75 80
    2 8.2 8.1 8.0 1.40 1.44 1.48
    7 9.5 9.4 9.3 1.41 1.45 1.50
    12 10.8 10.7 10.6 1.43 1.47 1.51
    17 12.1 12.0 11.9 1.44 1.49 1.53
    22 12.9 12.8 12.6 1.47 1.51 1.55
    27 13.7 13.5 13.4 1.49 1.53 1.58
    32 14.5 14.3 14.2 1.51 1.55 1.60
    37 15.8 15.6 15.5 1.53 1.57 1.62
    42 17.9 17.7 17.6 1.53 1.58 1.62
    47 20.0 19.8 19.6 1.54 1.58 1.63
    52 21.3 21.1 20.9 1.55 1.60 1.65
    57 22.6 22.4 22.2 1.57 1.62 1.66
    62 24.0 23.7 23.5 1.59 1.63 1.68
    67 25.3 25.0 24.8 1.60 1.65 1.70
    72 26.6 26.3 26.1 1.62 1.67 1.72

    You might ask your installing pro if he can get you a copy of publication PUB. NO. 22-1754-02-0305. That will be formatted in a way that is easier to read.

    Sorry about the poor formatting but you can figure out that it's a bit over 1500W under ideal circumstances. What I don't know is, the draw of your heat strips, or what factors make your actual installation different from the manual specs. I'm not a pro just a homeowner who has sticky fingers when it comes to collecting information.

    Hope this helps -- Pstu

  3. #3
    Join Date
    Nov 2008
    Posts
    1,673
    Quote Originally Posted by Ziocarl View Post
    Just trying to figure out how much the thing costs to run for an hour.
    http://en.wikipedia.org/wiki/Electricity_meter
    Take meter wattage readings over a one hour time difference over several days or weeks.

    Please post all your numbers.
    There is information in their variation from reading to reading.
    "Standard deviation is a widely used measure of the variability or dispersion"

    TIA

  4. #4
    Join Date
    Dec 2008
    Posts
    103


    Why did I think there might be a simple answer for once?

    Thanks for looking up the info. I'm just overwhelmed by it.



    Let's just say that it's 1500 watts.... So do you mean to tell me that if I run the heatpump (non auxilary mode) for 1 hour, I'll be using as much electricity as my littel portable 1500 watt space heater running for an hour? That's freaking amazing!! If so, I'll never use the space heater again.

    Somehow I don't think that's right though.

    Oh and reading my meter doesn't soudn like the answer. That would give me real world info just for that moment in time. It would reflect a whole host of other devices in the house and I wouldn't be able to control which stage the heatpump was in and if it was running constantly. I just want a theoretical number for my heatpump running constantly in each stage.

  5. #5
    Join Date
    Sep 2006
    Posts
    1,253
    Quote Originally Posted by Ziocarl View Post


    Why did I think there might be a simple answer for once?

    Thanks for looking up the info. I'm just overwhelmed by it.



    Let's just say that it's 1500 watts.... So do you mean to tell me that if I run the heatpump (non auxilary mode) for 1 hour, I'll be using as much electricity as my littel portable 1500 watt space heater running for an hour? That's freaking amazing!! If so, I'll never use the space heater again.

    Somehow I don't think that's right though.

    Oh and reading my meter doesn't soudn like the answer. That would give me real world info just for that moment in time. It would reflect a whole host of other devices in the house and I wouldn't be able to control which stage the heatpump was in and if it was running constantly. I just want a theoretical number for my heatpump running constantly in each stage.
    No, what pstu has posted is correct and actually better than the generalizations made. If you follow the line across in the 1st stage numbers that starts with 27 you will see the number 1.24. That number is the kW used. You will also see the number 10.4 right after the 27. That is the about of BTUs you get for 1.24kW at 27*F. In other words you get 10,400 BTUs for 1,240 watts of electricity at 27*F.

    Now, that little 1,500 watt space heater is only giving you 5,100 BTUs.

    You now see the efficiency of a heat pump as compared to any other heating device. You get more out of it for less costs than any oil furnace, gas furnace, boiler, or electric resistive heat.

  6. #6
    Join Date
    Nov 2008
    Posts
    1,673
    Average heat loss for a house is 5.9 BTU/(sq. ft-HDD), with a range from 1.7 to 11.

    One hour of 30F counts as 35/24 HDD. Measure it at night.

    With a 2000 sq. ft. house you should have a 17,000 BTU loss in this hour, with a low value of 5,000 for a tight house, and a high value of 32,000. Your aux heat [at an efficiency of ~100%] is a good check for this value.

    Turn off everything in the house at the breakers except the heat pump for one hour or else measure your normal wattage draw during this hour and subtract from the reading.

    With these numbers you should be able to measure your avg. COP during the hour, and with several readings the effects of wind, rain, etc. should cancel out.

    Whaddya' bet the real world measurements come out worse than the manuf's stated figures?

  7. #7
    Join Date
    Apr 2009
    Posts
    523
    Too many variables. Outside temp being one of the biggest.

    Regardless I have a dual fuel set up and before that Gas and AC. But there was NO circumstance where it made sense to have a space heater. I actually wanted one, something about a little heater I find neat and somewhat relaxing.

    Electric heat in any of its forms is expensive. And while a heat pump aux heat is more expensive, its doing more. Keep in mind electric is 100% efficient. So with more expense comes more heat, your just heating the entire house.

    And its pretty much always less expensive to heat with the heat pump even if it does have to run longer.

    The only circumstance is if you were flat broke and just locked yourself in one room and heated at minimum with a space heater then it would work out for you...

    The bad thing about heating one room at a time is there is no insulation between rooms, dry wall, dead space, more dry wall, room. So you are usually better heating everything with a properly operating heat pump.

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