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  1. #14
    Join Date
    Aug 2003
    Location
    Lincoln, Nebraska
    Posts
    1,051
    You can't run a gas furnace and heat pump at the same time.
    Its a good Life!

  2. #15
    Join Date
    Oct 2007
    Posts
    21
    I just spoke with my installer and he said that at the classes he went to from Bryant, they calculated an economic balance point of about 28 degrees for this area (Michigan). He said one of the factors making the heat pump more costly at the lower temperatures is the added electricity for the defrost cycle. He is going to revisit this whole issue with the Bryant rep and get back with me.
    Last edited by adamsdp; 11-13-2007 at 10:52 AM. Reason: spelling

  3. #16
    Join Date
    May 2007
    Location
    Upstate SC
    Posts
    188
    I assume this is correct. I know it is for my system.

  4. #17
    I am in Minnesota and have a very similar system to yours.

    A lot goes in to figureing out where to set the lockout. Typically I see most of my dealers setting it at 25 but I run mine down to 20 since I have a zoned system and I keep my house around 68.

    you could set it at none but then the heatpump would run for 25 minutes before the furnace would come on-thus fighting a losing battle.

  5. #18
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,435

    Question C.O.P. for BRYANT Heat Pump in mid 20'F

    Quote Originally Posted by adamsdp View Post

    I am looking for the best Economic balance point.

    From some of the replies it sounds maybe I should go back to the default setting of no heat pump lockout temperature and just allow the furnace to come on when the heat pumpt cannot keep up with the heating demands?

    I am going to pursue trying to figure out at what temperature the furnace will become more economical to run than the heat pump.

    It sounds an approximation might be the best one can do, but I still think it will be useful information. Thanks.
    Economic balance point is not hard to determine once you know your utility rates and
    heat pump C.O.P. in the temperature range of interest.

    Calculated Economic balance point is likely clsoe to the 3-ton 15 SEER/8.4 HSPF heat pump / 2,000 sq. foot residence Heating Balance Point.
    Calculated Economic balance point does not accurately account for the defrost cycle.

    S.E. Michigan
    Electric Rate ... ... ... $0.11 / kW
    = 100,000 BTU/therm / 3413 BTU/ kW = 29.3 kW/ Therm
    $3.22 / 100,000 BTU

    http://www.michigan.gov/mpsc/0,1607,...5189--,00.html

    specific C.O.P. ascertained for BRYANT heat pump 286-036 ( assumed same as CARRIER Performance Series)
    Effective cost = $1.15 at C.O.P. of 2.8 @ 27'F)

    xxxxxxxxxxxxx
    Natural Gas ... ... ... .. $1.00 / Therm
    http://www.dleg.state.mi.us/mpsc/gas/rates/gasrates.pdf

    Therm = 100,000 BTU
    at 95 % efficiency .. $1.053 / 100,000 BTUh

    K.I.S.S.

    Economic balance point = ~ 33' F ... Moderate-High electric rate versus relatively low Natural Gas cost pushes the economic balance point
    higher than I would have anticipated for a HSPF 8.4 system.
    C.O.P. at 22'F - 28'F seems to be LOW. Perhaps, someone has an accurate ARI rating in this range.
    C.O.P. values below were interpolated from the 47'F - 17'F data to show cost comparison /Economic Balance Point.

    Based on review BRYANT (CARRIER PERFORMANCE Series) equipment specs.
    ________________________ $3.22 $0.11 29.3

    ..'F C.O.P. Effective
    47 __ 3.60 ___ $0.895
    46 __ 3.56 ___ $0.905
    45 __ 3.52 ___ $0.916
    44 __ 3.48 ___ $0.926
    43 __ 3.44 ___ $0.937
    42 __ 3.40 ___ $0.948
    41 __ 3.36 ___ $0.959
    40 __ 3.32 ___ $0.971
    39 __ 3.28 ___ $0.983
    38 __ 3.24 ___ $0.995
    37 __ 3.20 ___ $1.007
    36 __ 3.16 ___ $1.020
    35 __ 3.12 ___ $1.033
    34 __ 3.08 ___ $1.046
    33 __ 3.04 ___ $1.060
    32 __ 3.00 ___ $1.074
    31 __ 2.96 ___ $1.089
    30 __ 2.92 ___ $1.104
    29 __ 2.88 ___ $1.119
    28 __ 2.84 ___ $1.135
    27 __ 2.80 ___ $1.151
    26 __ 2.76 ___ $1.168
    25 __ 2.72 ___ $1.185
    24 __ 2.68 ___ $1.203
    23 __ 2.64 ___ $1.221
    22 __ 2.60 ___ $1.240
    21 __ 2.56 ___ $1.259
    20 __ 2.52 ___ $1.279
    19 __ 2.48 ___ $1.300
    18 __ 2.44 ___ $1.321
    17 __ 2.40 ___ $1.343
    Last edited by dan sw fl; 11-13-2007 at 09:54 PM. Reason: Add C.O.P. Table
    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

  6. #19
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    Quote Originally Posted by m kilgore View Post
    You can't run a gas furnace and heat pump at the same time.

    hey uhhhh big timer, they both run when defrost kicks in,(if wired properly)!



    .

  7. #20

    Question

    How do you change the balance point?

  8. #21
    Join Date
    Aug 2003
    Location
    Lincoln, Nebraska
    Posts
    1,051
    duh....I wasn't talking during defrost.
    Its a good Life!

  9. #22
    Join Date
    Jan 2002
    Location
    East Grand Forks, MN
    Posts
    1,375
    I am looking for the best Economic balance point.

    Think of this a constructive criticism reply.

    First you needed to have done a HeatLoad calculation, especially by your contractor! You need this to figure out your particular thermal balance pt and your economic balance pt. And this brings me to, how in h-- did they figure out your equipment sized??? The Evolution is a great system, but it doesn't mean you are getting the best system for your house!!!

    !!It's very important to sized a whole system and fit it to your existing home!!

    Now the equipment: The economic balance pt must be less than your thermal balance point. But how would you know that if you don't have a LoadCalc to guide you!
    With a loadcalc in one hand and the right equipment selected to meet the need for efficiency and comfort's sake, you can determine 1. how much the heat pump can handle (at what temp pt to shut off), 2. when you want the gas furnace to come on (at what temp pt to turn on), and 3. if supplemental heat is required (sometimes it cost less to run the heatpump and resistive heat together than a gas furnace to a certain pt.).

    But i could be all wrong about this idea if the Hybrid Heat system has a minicomputer built-in to figure this all out!

    Good Luck with your new Hybrid Heat!!

  10. #23
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,435

    Thumbs up Get It Together !

    Quote Originally Posted by wormie1205 View Post
    How do you change the balance point?
    With
    __ NEW house,
    __ ___ NeW equipment,
    __ ___ ____ electric rate change, or gas cost decrease.
    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

  11. #24
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    Quote Originally Posted by m kilgore View Post
    duh....I wasn't talking during defrost.
    duh, never say cant!



    .

  12. #25
    Join Date
    May 2007
    Location
    Upstate SC
    Posts
    188
    Arc8 - Nice way to tie together the two types of balance points.

    About that minicomputer figuring it all out. I read in an online home magazine the other day that there is a system that allows you to tell the tstat what the cost per KWh you pay for electrcity and what the cost per therm you pay for natural gas, and it figures out what the economic switchover point is. Anyone hear of that? The article didn;t mention brand names, it just gave the impression that that methods is the standard for todays high end systems. I did not think this was the case, but figured someone must make a tstat that allows that. It's a simple calc for a minicomputer.

  13. #26
    Join Date
    Oct 2007
    Posts
    21
    Here in SE Michigan, the D1.7 electric rate (space conditioning) for heat pumps is about $.065 for summer and $.037/kWh for winter. Where did
    you get the Bryant Equipment specs from? Your calculations below look very helpful. Thanks.



    Quote Originally Posted by dan sw fl View Post
    Economic balance point is not hard to determine once you know your utility rates and
    heat pump C.O.P. in the temperature range of interest.

    Calculated Economic balance point is likely clsoe to the 3-ton 15 SEER/8.4 HSPF heat pump / 2,000 sq. foot residence Heating Balance Point.
    Calculated Economic balance point does not accurately account for the defrost cycle.

    S.E. Michigan
    Electric Rate ... ... ... $0.11 / kW
    = 100,000 BTU/therm / 3413 BTU/ kW = 29.3 kW/ Therm
    $3.22 / 100,000 BTU

    http://www.michigan.gov/mpsc/0,1607,...5189--,00.html

    specific C.O.P. ascertained for BRYANT heat pump 286-036 ( assumed same as CARRIER Performance Series)
    Effective cost = $1.15 at C.O.P. of 2.8 @ 27'F)

    xxxxxxxxxxxxx
    Natural Gas ... ... ... .. $1.00 / Therm
    http://www.dleg.state.mi.us/mpsc/gas/rates/gasrates.pdf

    Therm = 100,000 BTU
    at 95 % efficiency .. $1.053 / 100,000 BTUh

    K.I.S.S.

    Economic balance point = ~ 33' F ... Moderate-High electric rate versus relatively low Natural Gas cost pushes the economic balance point
    higher than I would have anticipated for a HSPF 8.4 system.
    C.O.P. at 22'F - 28'F seems to be LOW. Perhaps, someone has an accurate ARI rating in this range.
    C.O.P. values below were interpolated from the 47'F - 17'F data to show cost comparison /Economic Balance Point.

    Based on review BRYANT (CARRIER PERFORMANCE Series) equipment specs.
    ________________________ $3.22 $0.11 29.3

    ..'F C.O.P. Effective
    47 __ 3.60 ___ $0.895
    46 __ 3.56 ___ $0.905
    45 __ 3.52 ___ $0.916
    44 __ 3.48 ___ $0.926
    43 __ 3.44 ___ $0.937
    42 __ 3.40 ___ $0.948
    41 __ 3.36 ___ $0.959
    40 __ 3.32 ___ $0.971
    39 __ 3.28 ___ $0.983
    38 __ 3.24 ___ $0.995
    37 __ 3.20 ___ $1.007
    36 __ 3.16 ___ $1.020
    35 __ 3.12 ___ $1.033
    34 __ 3.08 ___ $1.046
    33 __ 3.04 ___ $1.060
    32 __ 3.00 ___ $1.074
    31 __ 2.96 ___ $1.089
    30 __ 2.92 ___ $1.104
    29 __ 2.88 ___ $1.119
    28 __ 2.84 ___ $1.135
    27 __ 2.80 ___ $1.151
    26 __ 2.76 ___ $1.168
    25 __ 2.72 ___ $1.185
    24 __ 2.68 ___ $1.203
    23 __ 2.64 ___ $1.221
    22 __ 2.60 ___ $1.240
    21 __ 2.56 ___ $1.259
    20 __ 2.52 ___ $1.279
    19 __ 2.48 ___ $1.300
    18 __ 2.44 ___ $1.321
    17 __ 2.40 ___ $1.343

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