Page 3 of 3 FirstFirst 123
Results 27 to 33 of 33
  1. #27
    Join Date
    Oct 2007
    Posts
    21
    Thanks for your reply and I am trying to learn as I go, along with the contractor. I think hybrid systems are fairly new to this area as 3 out of the 4 contractors I had come out said that they had heard of heat pumps but weren't familar with them. The contractor I hired has the most experience in this area with heat pumps but is still learning. The Evolution thermostat does not calculate the best balance point but has a lot of other nice features as far as I can tell being a newcomer to this field. I will see if I can track down the LoadCalc software.

    Quote Originally Posted by arc8 View Post
    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!!
    Last edited by adamsdp; 11-14-2007 at 08:08 PM. Reason: spelling

  2. #28
    Join Date
    Oct 2007
    Posts
    21
    Under the advanced settings there is a selection where you can choose a heat pump lockout temperature. I think it is under Advanced/Settings/Hybrid Heat. If you can't find it let me know and I will try it again at home and reply.
    My default setting was none which I think means the heat pump would run as long as it could keep up with heating demands and then switch to the furnace if it could not keep up. I have set mine for 28 deg for now.

    Quote Originally Posted by wormie1205 View Post
    How do you change the balance point?

  3. #29
    Join Date
    Oct 2007
    Posts
    21
    My contractor spoke with the local Bryant rep and he said that there are two schools of thought on the balance point for this area - SE Michigan. One is that you have no heat pump lockout temp selected and let the heat pump run as much as possible until it can't keep up and then the furnace will take over as the heat pump will be cheaper to run than the furnace at any outdoor temperature that the heat pump can provide heat for. The other school is that the defrost cycle uses a good amount of electricity and also to save wear and tear on the heat pump, a balance point of 28-30 is a good setting. My contractor said they don't have a long history of information to go on in this area about the wear and tear/defrost cycle but he is going to look for software to provide more guidance.

  4. #30
    Since I am a BRyant rep please go to page 2 and read my reply. you are way overthinking this decision. I think a good train of thought for you is to lower it until it in not able to keep you comfortable and then move it up a couple of degrees.

    If not please set it at 20 and go from there

  5. #31
    Join Date
    Oct 2007
    Location
    KY
    Posts
    59
    Quote Originally Posted by stopro1 View Post
    There is no reasonable economic balance point where the fossil fuel furnace is more efficient than the heat pump, until it's about -10F outside, (equal to the furnace). Balance point is and always will be the point where there the heat pump can no longer satisfy the heating demand alone. When the room temp falls below the setpoint, you have fallen below the balance point, and will require back-up heating to maintain the same setpoint.
    You write that:
    "when the heat pump's COP is at .95 "

    The factor that you have not consideed in your analysis is the Cost of Power.

    However, the Conversion of Power (COP) is only one factor in the equation.
    At lower temps the Heat Pump COP becomes very low - you sited 0.95.
    If raw energy cost (BTU cost) from electricty is 2X the NG cost, the cross over point for the cost of home heating will not be the heat pump COP number.

    Neither of those consider the "comfort factor" of having blowing hot air, and that is homeowner subjective.

  6. #32
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    5,998
    Quote Originally Posted by aaCharley View Post
    You write that:
    ... However, the Conversion of Power (COP) is only one factor in the equation.
    C.O.P. = Coeffficient Of Performance

    http://en.wikipedia.org/wiki/Coefficient_of_performance
    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

  7. #33
    Join Date
    Oct 2007
    Location
    KY
    Posts
    59
    Thanks for the correction and the useful link to the proper definition.

    The coefficient of performance, or COP (sometimes CP), of a heat pump is the ratio of the output heat to the supplied work . . . .

    Conversion of Power is not correct - just the way I think of it.

    That COP number is variable, depending upon the outside air temp. The Wikipedia example uses a geothermal source which would have very little variability.

Page 3 of 3 FirstFirst 123

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