Page 1 of 5 12345 LastLast
Results 1 to 13 of 60
  1. #1
    Join Date
    Mar 2007
    Posts
    55

    Is high energy usage normal when heating with XL-16i?

    Hi! Last May, I had a 3-ton Trane XL-16i unit installed with electric resistance as the backup heat and a new Trane thermostat (that seems to be set correctly to 3 stage heating/2 stage cooling). This replaced a Trane XE1000 unit of the same size and the same amount of resistance heating. During the summer and fall I noticed that the electric bill was down about 20%-25% when all cooling was needed. As late fall approached and mild heating was needed (never getting off of first stage), the electric usage was still down about 15-20%. But last month and especially this month as temperatures have continued to get colder here in SW Ohio, the electric usage has increased to higher than what the old unit had used. It seems that when this unit is running in second stage for long periods of time, it is definitely less efficient than the old unit. And on days when the auxillary heat is needed some, it gets even worse (which I expect). On a relatively cold day with highs in the 20's and lows in the single digits, energy usage from the heat pump is about 160-170+ KWH per day (and that's with one of the heat banks turned off as recommended by my installer to try to lower energy consumption) while regular day to day usage around the house with appliances, etc adds another 30-35 KWH. During the last 30 days, the average temperature has been 31 degrees and I've used a total of 3,800 KWH. With the old heat pump and a similar average temperature, I was using about 3,000 KWH total. The worst bill with the old heat pump was during a month that had an average temperature of 19 degrees and the total usage then was only 4,400 KWH. If we had a similar month that cold with this heat pump, I would guesstimate that I'd probably use about 5,500-6,000 KWH.

    I have the temperature in the house set to 68 degrees. When the temperature drops down into the low to mid 20's, 2nd stage begins to run constantly or almost constantly. Then as the temperature drops down to about 20, I notice that the aux heat will begin to occasionally kick on and off. When it is about freezing out, the output temperature at a register is about 80 degrees on 1st stage and about 84 degrees on 2nd stage. From what I can tell, switching from 1st to 2nd stage adds about 3-4 degrees to the output temperature. Everything appears to be running correctly and the temperature in the house is being maintained.

    When the 16i is running 2nd stage constantly, should it be less efficient than my old XE1000 unit? I would have expected a savings every month of the year but the way it's looking, I'll be paying higher electric bills during the colder winter months (probably from December - March) when 2nd and 3rd stage is being used. With a unit that is supposed to be so efficient with heating, I would have expected better. The way it seems, maybe I would have been better off saving money and getting a 14i or 15i. What's nice is that I have until May to decide since the installer I went with has a 1 year money back guarantee. But then the question will come up with what unit I should have installed next.

    Is there something wrong that I can check or have my installer check? He was out just last month and said everything looked really good. He ran several tests, including the temperatures and everything was really good including the amount of BTU's being produced.

    Any help or advice anyone can provide would be great. Thanks!

    Aaron

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,097
    The charge should be rechecked.
    I think you'll find your old XE1000 had a better heat rating then the 16i's do.

    Have your installer reconnect that other bank of strip heat, and lower the CPH for it, and secondstage.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Mar 2007
    Posts
    55
    I will go ahead and turn the second bank back on...The installer just turned it off at my circuit breaker box. As far as the heat rating is concerned, I guess I'm a bit confused how the XE1000 which had an HSPF of 7.5 (at least that's what my installer told me) would have a better heat rating than an HSPF of 9. Is there someplace I can go to check out the heat rating of different units?

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,097
    You'll have a hard time finding the rating of your old unit.
    ari.org will have the ratings of your new unit.

    The 16i has a good heat to wattage output(HSPF), but the BTU's of heat you get aren't a lot. So it runs longer to give you less heat, and the strips have to come on quicker to make up for it.

    Your old unit would have had a lower number because it used more watts per BTU outputi. But it also put out more BTU's at lower temps then the 16i. So your strips weren't needed as often, or as long.

    Again, an incorrect charge can also cause high heating bills from a heat pump.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  5. #5
    Join Date
    Mar 2007
    Posts
    55
    I checked the cph settings for each stage and here is what they are currently set to:
    1st stage = 3
    2nd stage = 3
    3rd stage = 9

    Any recommendations of what each stage should be set to?

    I know last month when they came out and checked everything including the charge, the installer said it was normal. I have the sheet showing all of the things they tested along with the numbers measured...What should the charge be for this unit?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,097
    I'd set stage 3 to 3 also.
    At 9, it cycles way too much, and cost more.

    The charge readings are not a set pressure, but pressure and temps.
    Temp indoor and outdoor. Line pressures and line temps.
    If they just have pressure, it doesn't mean much.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #7
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295

    TRANE Heat Pumps

    Quote Originally Posted by s012adh View Post
    As far as the heat rating is concerned, I guess I'm a bit confused how the XE1000 which had an HSPF of 7.5 (at least that's what my installer told me) would have a better heat rating than an HSPF of 9. Is there someplace I can go to check out the heat rating of different units?
    Heating Performance Rating
    at 70'F Indoor Temp. and 1200 CFM

    ___ XR14 _______________ XL16i
    4TWR4036 ________ 4TWX6036
    Temp _ kW BTUh___ kW BTUh * 1,000

    47 _ 2.81 31.8 ____ 2.39 33.2
    42 _ 2.73 28.2 ____ 2.34 30.6
    37 _ 2.65 24.5 ____ 2.29 28.1
    32 _ 2.62 22.6 ___ 2.26 26.2
    27 _ 2.61 21.0 ____ 2.24 24.9
    22 _ 2.60 21.1 ____ 2.22 23.5

    Obviously, your performance is not exactly what you wish.
    (at about feezing out ... 84' - 68' = 16' = dT actual)

    Q = 1.08 * dt * CFM
    dT = Q / ( 1.08 * CFM)
    at 32'F your heat rise should theoretically be ~20.2'F
    = 26,200 /( 1.08 * 1200)

    It appears that the charge may be causing the unit to
    underperform by ~ 20%.

    Send me an e-mail ( in profile) if you wish to see the XR14 and XL16i catalogs.
    (semi-large [ 1 MB] PDF files)
    Last edited by dan sw fl; 01-27-2008 at 07:40 PM. Reason: XR14 above not XL14i (which is added below)
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295

    Confused

    Quote Originally Posted by s012adh View Post
    a 3-ton Trane XL-16i unit installed with electric resistance as the backup heat and a new Trane thermostat (that seems to be set correctly to 3 stage heating/2 stage cooling).

    I have the temperature in the house set to 68 degrees.

    When the temperature drops down into the low to mid 20's, 2nd stage begins to run constantly or almost constantly. Then as the temperature drops down to about 20, I notice that the aux heat will begin to occasionally kick on and off.

    When it is about freezing out, the output temperature at a register is about 80 degrees on 1st stage and about 84 degrees on 2nd stage.

    I would have expected a savings every month of the year but the way it's looking, I'll be paying higher electric bills during the colder winter months (probably from December - March) when 2nd and 3rd stage is being used.

    With a unit that is supposed to be so efficient with heating, I would have expected better. The way it seems, maybe I would have been better off saving money and getting a 14i or 15i. What's nice is that I have until May to decide since the installer I went with has a 1 year money back guarantee. But then the question will come up with what unit I should have installed next.

    Is there something wrong that I can check or have my installer check?
    Thanks! Aaron
    Switching to a 14i will not improve energy cost unless the charge is correct.

    Based on ratings,
    XL 16i should be 34% better than a XR14 at 32'F

    _kw ___BTU//kW "BTU "Output" _ C.O.P.
    ________________ 26,200
    2.26 3413 7713.38 _____3.397
    2.62 3413 8942.06 _____2.527 1.344
    ________________ 22, 600


    26,200 BTUh
    1,296 20.216'F dT

    1.08* CFM = 1,296

    4TWX6036B1 WITH 4TEE3F40A1 AT 1200 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 16.7 16.5 16.4 ___ 2.10 2.16 2.22
    7 18.5 18.3 18.2 ___ 2.13 2.19 2.26
    12 20.4 20.2 20.0 ___ 2.16 2.23 2.29
    17 22.2 22.0 21.8 ___ 2.19 2.26 2.33
    22 23.5 23.3 23.1 ___ 2.22 2.28 2.35
    27 24.9 24.6 24.4 ___ 2.24 2.30 2.37
    32 26.2 26.0 25.7 __ 2.26 2.33 2.39
    37 28.1 27.8 27.5 ___ 2.29 2.36 2.43
    42 30.6 30.3 30.1 ___ 2.34 2.41 2.48
    47 33.2 32.9 32.6 ___ 2.39 2.46 2.53
    52 35.0 34.7 34.4 ___ 2.42 2.49 2.56
    57 36.9 36.5 36.2 ___ 2.45 2.52 2.60
    62 38.7 38.3 38.0 ___ 2.48 2.55 2.63
    67 40.5 40.1 39.8 ___ 2.51 2.59 2.66

    4TWX4036B1 WITH 4TEE3F37A1 AT 1200 CFM
    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 18.7 18.5 18.3 __ 2.77 2.86 2.94
    7 20.2 20.0 19.8 ___ 2.77 2.85 2.93
    12 21.7 21.4 21.2 ___ 2.76 2.84 2.93
    17 23.1 22.9 22.7 ___ 2.76 2.84 2.92
    22 24.5 24.3 24.1 ___ 2.79 2.87 2.96
    27 26.0 25.7 25.5 ___ 2.82 2.91 2.99
    32 27.4 27.1 26.8 __ 2.86 2.94 3.03
    37 28.8 28.6 28.3 ___ 2.85 2.94 3.02
    42 30.4 30.1 29.8 ___ 2.79 2.87 2.95
    47 32.0 31.7 31.4 ___ 2.72 2.80 2.88
    52 33.5 33.1 32.8 ___ 2.71 2.79 2.87
    57 35.0 34.6 34.3 ___ 2.70 2.79 2.87
    62 36.4 36.1 35.7 ___ 2.70 2.78 2.86
    67 37.9 37.5 37.2 ___ 2.69 2.77 2.85
    72 39.4 39.0 38.6 ___ 2.69 2.77 2.85
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  9. #9
    Join Date
    Mar 2007
    Posts
    55
    Where is the "proper" place to measure the temperature to get an accurate gauge of the change in temperature? I know that with the measurements on the sheet that the installer provided to us, he measured the supply temperature in our crawl space someplace and then used the temperature that we had the thermostat set on to determine the temperature difference? I know that when he came out last month, that he wrote the supply temperature down as 92 (with an outside temperature of 41) although at that temperature I've only seen the temperature at the register be about 85-86. The ducting is well-insulated so is it possible to lose that much heat at a register that's 15' from the furnace? Even further away from the furnace, the temperature at the register is about the same. Or is there someplace that I can easily check coming directly out of the furnace to see if the installer's readings were correct? Based on the formula given, I should be seeing a temperature difference of 23-24 and using the installer's supply temperature of 92 and the intake temperature of 68, you get that.

  10. #10
    Join Date
    Jan 2007
    Location
    Minneapolis, MN
    Posts
    415
    Was the air flow through the unit actually measured? Improper airflow will affect unit capacity. Also charge cannot be properly adjusted without the correct airflow. Most assume 400 cfm per ton but do not confirm it.

  11. #11
    Join Date
    Dec 2007
    Location
    oregon
    Posts
    885
    Quote Originally Posted by mbarson View Post
    Was the air flow through the unit actually measured? Improper airflow will affect unit capacity. Also charge cannot be properly adjusted without the correct airflow. Most assume 400 cfm per ton but do not confirm it.
    Use a true flow plate in the filter rack or filter grille.
    Genius = The guy who can do anything...except make a living!

  12. #12
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295

    Unhappy Testing

    Quote Originally Posted by s012adh View Post
    I know that when he came out last month, that he wrote the supply temperature down as 92 (with an outside temperature of 41) although at that temperature I've only seen the temperature
    at the register be about 85-86.

    Or is there someplace that I can easily check coming directly out of the furnace to see if the installer's readings were correct?

    ... intake (return air) temperature of 68,
    Check the Supply Air temepraute directly at the air handler outlet
    ... through a very small hole in the duct with a wire temperature probe

    'F Rated BTUh ___ kW ... C.O.P.
    42 ___ 30,600 __ 2.34 .. 3.83

    30,600 BTUh/ 1,296 CFM = 23.6'F dT at 42'F

    dT is only accurate/meaningful IF you also know the total air flow.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  13. #13
    Join Date
    Mar 2007
    Posts
    55
    The airflow was measured to be 1202 CFM.

Page 1 of 5 12345 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event