Heat Pump - Should compressor run when it's 20 degrees outside?

Discussion in 'HVAC' started by Greg, Jan 9, 2004.

  1. Greg

    Greg Guest

    Should my new Carrier heat pump compressor (the outside unit) really be
    running when it is 20 degrees F outside? I thought they were only effective
    down to 40 degrees or so, and after that the system really relied on
    auxiliary heat. My Aux Ht does come on, and the house is warm enough, I'm
    just wondering if the compressor is wasting electricity or wearing itself
    out to no good effect. Should I call my contractor? Thanks. greg
    Greg, Jan 9, 2004
    #1
  2. "Greg" <> wrote in message
    news:...
    > Should my new Carrier heat pump compressor (the outside unit) really be
    > running when it is 20 degrees F outside? I thought they were only

    effective
    > down to 40 degrees or so, and after that the system really relied on
    > auxiliary heat. My Aux Ht does come on, and the house is warm enough, I'm
    > just wondering if the compressor is wasting electricity or wearing itself
    > out to no good effect. Should I call my contractor? Thanks. greg


    I believe the heat pump's efficiency has improved over the years. You
    should be fine down to around 10 deg. See how it performs and call your
    contractor if it doesn't meet your expectations for comfort and utility
    usage.

    - Robert
    American Mechanical, Jan 9, 2004
    #2
  3. Greg

    TURTLE Guest

    "Greg" <> wrote in message
    news:...
    > Should my new Carrier heat pump compressor (the outside unit) really be
    > running when it is 20 degrees F outside? I thought they were only

    effective
    > down to 40 degrees or so, and after that the system really relied on
    > auxiliary heat. My Aux Ht does come on, and the house is warm enough, I'm
    > just wondering if the compressor is wasting electricity or wearing itself
    > out to no good effect. Should I call my contractor? Thanks. greg
    >


    This is turtle.

    Like Robert said the Heat pump will work down to 10 degree F or less but
    what your wanting to know is the heat pump will heat down to 10 degree or
    less but the heat pump becomes not cost effective at about 10ºF or less. The
    heat pump is cost effective above 10ºF or higher. The straight electic heat
    strips will be cheaper to run below 10ºF of outdoor temperatrure.

    Now you say you had a new heat pump installed lately and i as a hvac
    installer / everything hvac/r . You can call the installer and ask him any
    question you want and not cost you a dime. they should answer any question
    you want answered or answer any question you are asking here. You can even
    ask them " Should i call you to come look at it because it is doing this or
    that". Call them up and discuss anything you want too for In this business
    your suppose to answer any question a customer has to ask and answer with
    Respect.

    TURTLE
    TURTLE, Jan 9, 2004
    #3
  4. Greg

    mccaldwell Guest

    My house's balance point in mid-Atlantic is around 20, and outside
    thermostat presently set to lock out aux heat above this point. May
    raise it a bit to speed up recovery on cold mornings. Even then, aux
    only assists. Heat pump has a positive efficiency down to about 0.



    "Greg" <> wrote in message news:<>...
    > Should my new Carrier heat pump compressor (the outside unit) really be
    > running when it is 20 degrees F outside? I thought they were only effective
    > down to 40 degrees or so, and after that the system really relied on
    > auxiliary heat. My Aux Ht does come on, and the house is warm enough, I'm
    > just wondering if the compressor is wasting electricity or wearing itself
    > out to no good effect. Should I call my contractor? Thanks. greg
    mccaldwell, Jan 9, 2004
    #4
  5. Greg

    Guest

    WHen heat pumps first made their way into the market...back in the late
    50's... the manufacturers used to let the compressors run all the time
    regardless of outside temps. They found out later, that, there reaches
    a point when its not beneficial against the cost of running the
    compressor.
    , Jan 9, 2004
    #5
  6. Greg

    JB Books Guest

    "TURTLE" <> wrote in message news:<btmp0p$8gr13$-berlin.de>...
    > "Greg" <> wrote in message
    > news:...
    > > Should my new Carrier heat pump compressor (the outside unit) really be
    > > running when it is 20 degrees F outside? I thought they were only

    > effective
    > > down to 40 degrees or so, and after that the system really relied on
    > > auxiliary heat. My Aux Ht does come on, and the house is warm enough, I'm
    > > just wondering if the compressor is wasting electricity or wearing itself
    > > out to no good effect. Should I call my contractor? Thanks. greg
    > >

    >
    > This is turtle.
    >
    > Like Robert said the Heat pump will work down to 10 degree F or less but
    > what your wanting to know is the heat pump will heat down to 10 degree or
    > less but the heat pump becomes not cost effective at about 10ºF or less. The
    > heat pump is cost effective above 10ºF or higher. The straight electic heat
    > strips will be cheaper to run below 10ºF of outdoor temperatrure.
    >
    > Now you say you had a new heat pump installed lately and i as a hvac
    > installer / everything hvac/r . You can call the installer and ask him any
    > question you want and not cost you a dime. they should answer any question
    > you want answered or answer any question you are asking here. You can even
    > ask them " Should i call you to come look at it because it is doing this or
    > that". Call them up and discuss anything you want too for In this business
    > your suppose to answer any question a customer has to ask and answer with
    > Respect.
    >
    > TURTLE


    straight electric strips with a cop of one will never be cheaper to
    run that a heat pump with a cop off three. now the heat pump should
    run as long as it can keep up with the heat loss for the most savings.
    once you go below the balance point the heat pump will no longer keep
    up to the heat loss and some kind of aux second stage added super
    dooper booster rocket heater will be needed to keep the house warm.
    the balance point can vary widely depending on the actuall home and
    the region it is in and by the living habits of the occupants. so you
    are fine running at 20 and maybe lower than that.

    jb books
    JB Books, Jan 9, 2004
    #6
  7. Greg

    TURTLE Guest

    "JB Books" <> wrote in message
    news:...
    > "TURTLE" <> wrote in message

    news:<btmp0p$8gr13$-berlin.de>...
    > > "Greg" <> wrote in message
    > > news:...
    > > > Should my new Carrier heat pump compressor (the outside unit) really

    be
    > > > running when it is 20 degrees F outside? I thought they were only

    > > effective
    > > > down to 40 degrees or so, and after that the system really relied on
    > > > auxiliary heat. My Aux Ht does come on, and the house is warm enough,

    I'm
    > > > just wondering if the compressor is wasting electricity or wearing

    itself
    > > > out to no good effect. Should I call my contractor? Thanks. greg
    > > >

    > >
    > > This is turtle.
    > >
    > > Like Robert said the Heat pump will work down to 10 degree F or less but
    > > what your wanting to know is the heat pump will heat down to 10 degree

    or
    > > less but the heat pump becomes not cost effective at about 10ºF or less.

    The
    > > heat pump is cost effective above 10ºF or higher. The straight electic

    heat
    > > strips will be cheaper to run below 10ºF of outdoor temperatrure.
    > >
    > > Now you say you had a new heat pump installed lately and i as a hvac
    > > installer / everything hvac/r . You can call the installer and ask him

    any
    > > question you want and not cost you a dime. they should answer any

    question
    > > you want answered or answer any question you are asking here. You can

    even
    > > ask them " Should i call you to come look at it because it is doing this

    or
    > > that". Call them up and discuss anything you want too for In this

    business
    > > your suppose to answer any question a customer has to ask and answer

    with
    > > Respect.
    > >
    > > TURTLE

    >
    > straight electric strips with a cop of one will never be cheaper to
    > run that a heat pump with a cop off three. now the heat pump should
    > run as long as it can keep up with the heat loss for the most savings.
    > once you go below the balance point the heat pump will no longer keep
    > up to the heat loss and some kind of aux second stage added super
    > dooper booster rocket heater will be needed to keep the house warm.
    > the balance point can vary widely depending on the actuall home and
    > the region it is in and by the living habits of the occupants. so you
    > are fine running at 20 and maybe lower than that.
    >
    > jb books


    This is turtle.

    I'm here just reading with my mouth open as to the words of the Great JB.

    You say it is cheaper to run a heat pump in ambiant temperature of zero or
    less and the manufactors [ Carrier , trane, and Amana ] will tell you to
    turn the heat pump off at less than +10ºF and switch to straight electric
    heat because it is not cost effective [ not cheaper to run ] than the
    electric heat. Now they do say the +10ºf is cost effective over the straight
    heat pump.

    So i guess JB knows more than Carrier and the other manufactors but I will
    have to be a dumb ass and listen to Carrier and other manufactors.

    TURTLE
    TURTLE, Jan 10, 2004
    #7
  8. Greg

    Jabs Guest

    Dave,
    You must be pretty new to this industry cause if you were around back in the
    50's, you would know that those guys from back then learned A/C &
    refrigeration from the refrigeration bible 'Refrigeration, Air Conditioning
    & Cold Storage by Raymond C Gunther. Compared to today's journeyman, those
    HVACR guys from the 50's would wipe their asses with today's journeyman.

    Jabs


    <> wrote in message
    news:...
    > WHen heat pumps first made their way into the market...back in the late
    > 50's... the manufacturers used to let the compressors run all the time
    > regardless of outside temps. They found out later, that, there reaches
    > a point when its not beneficial against the cost of running the
    > compressor.
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    Jabs, Jan 10, 2004
    #8
  9. Greg

    TURTLE Guest

    "Jabs" <> wrote in message
    news:zrLLb.49319$...
    > Dave,
    > You must be pretty new to this industry cause if you were around back in

    the
    > 50's, you would know that those guys from back then learned A/C &
    > refrigeration from the refrigeration bible 'Refrigeration, Air

    Conditioning
    > & Cold Storage by Raymond C Gunther. Compared to today's journeyman,

    those
    > HVACR guys from the 50's would wipe their asses with today's journeyman.
    >
    > Jabs


    This is Turtle.

    I haven't heard it called the Bible in years with a big S.

    TURTLE
    TURTLE, Jan 10, 2004
    #9
  10. Greg

    Greg Guest

    Thank you all for the interesting and educational replies to my question.
    Greg

    "Greg" <> wrote in message
    news:...
    > Should my new Carrier heat pump compressor (the outside unit) really be
    > running when it is 20 degrees F outside? I thought they were only

    effective
    > down to 40 degrees or so, and after that the system really relied on
    > auxiliary heat. My Aux Ht does come on, and the house is warm enough, I'm
    > just wondering if the compressor is wasting electricity or wearing itself
    > out to no good effect. Should I call my contractor? Thanks. greg
    >
    >
    Greg, Jan 10, 2004
    #10
  11. Greg

    Guest

    Re: Heat Pump - Should compressor run when it's 20 degrees outsiJAB

    Jab,

    I only reported what i heard in tradeschool that when heat pumps first
    came out , the compressors ran continuously. I was in tradeschool back
    in 1976. So..ive been in the trade for 28 years.

    Dave
    , Jan 10, 2004
    #11
  12. On Sat, 10 Jan 2004 06:42:34 GMT, Steve Kraus
    <> wrote:

    >Just for my own education, when a heat pump is running at a temp below
    >where it's cost effective, where is the energy being lost or is it just in
    >the exposed lines and energy to run the fan? What I mean is, with
    >resistance heat you get one unit of heat energy for one unit of
    >electricity. With a heat pump running at efficient temperatures you get
    >several units of heat because you're just transporting it from the
    >outside. As the outside temp drops you get less and less. But shouldn't
    >you always get at least as much as you're putting into it? If you're
    >getting less heat energy out than electric energy you put in the difference
    >has to go somewhere so I guess that's the question. Turning the fan and
    >losses from the lines exposed to cold. Anything else? Just curious.
    >


    You can reach a point ( of cold outside ) where you're gaining
    so little heat, and at the same time losing energy ( as it converts to
    heat and gets lost outside ), that you have no net gain.

    For instance - some of the electricity you put into the
    compressor turns into heat there, as it will with any motor. If it's
    cold enough out, you can lose all that via the compressor casing.
    Also, the energy lost at the outside fan via the same means of motor
    heat will never be recaptured at all, ever.

    Paul ( pjm @ pobox . com ) - remove spaces to email me
    'Some days, it's just not worth chewing through the restraints,
    ya know ?'

    HVAC/R program for Palm PDA's
    Free demo now available online !! http://pmilligan.net/palm/
    Free superheat charts for 38 Ref's online at http://pmilligan.net/pmtherm/
    pjm@see_my_sig_for_address.com, Jan 10, 2004
    #12
  13. Greg

    Jabs Guest

    Re: Heat Pump - Should compressor run when it's 20 degrees outsiJAB

    Dave,
    I'm sorry, I didn't know you were a 20+ year journeyman. Had I known, I
    probably would have sucked-up to you a little bit more. Back when I started
    in the mid 1970's, the 20+ year journeymen that I worked under taught me how
    to set the heat-pump defrost timers to help keep the C.O.P. at a higher
    level. Back then, they even showed me how to use a low outside air
    temperature thermostat to by-pass the heat-pump's compressor from operating
    and use electric heaters instead. I guess maybe that's why I think so
    highly of those 1950's HVAC guys. However, nevertheless and moreover, I'm
    glad your here.

    Jabs


    <> wrote in message
    news:...
    > Jab,
    >
    > I only reported what i heard in tradeschool that when heat pumps first
    > came out , the compressors ran continuously. I was in tradeschool back
    > in 1976. So..ive been in the trade for 28 years.
    >
    > Dave
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    >
    Jabs, Jan 10, 2004
    #13
  14. Greg

    Jabs Guest

    Steve,
    Not to mention the heat-pump's defrost period too.

    Jabs


    "Steve Kraus" <> wrote in message
    news:sEWLb.1588$...
    > > For instance - some of the electricity you put into the
    > > compressor turns into heat there, as it will with any motor. If it's
    > > cold enough out, you can lose all that via the compressor casing.
    > > Also, the energy lost at the outside fan via the same means of motor
    > > heat will never be recaptured at all, ever.

    >
    > Yeah, that makes sense.
    Jabs, Jan 10, 2004
    #14
  15. Greg

    Guest

    Re: Heat Pump - Should compressor run when it's 20 degrees outsiJAB

    Jab,
    Thanks...its nice to be here too. This DG has a wealth of info to be
    shared and learned.

    Dave
    , Jan 11, 2004
    #15
  16. Greg

    JB Books Guest

    Re: Heat Pump - Should compressor run when it's 20 degrees outsiJAB

    wrote in message news:<>...
    > Jab,
    > Thanks...its nice to be here too. This DG has a wealth of info to be
    > shared and learned.
    >
    > Dave


    the first thing you need to learn is how to qoute. but i wont hold my
    breath on a webtv user.

    jb books
    JB Books, Jan 12, 2004
    #16
  17. Greg

    CBhvac Guest

    Re: Heat Pump - Should compressor run when it's 20 degrees outsiJAB

    "JB Books" <> wrote in message
    news:...
    > wrote in message

    news:<>...
    > > Jab,
    > > Thanks...its nice to be here too. This DG has a wealth of info to be
    > > shared and learned.
    > >
    > > Dave

    >
    > the first thing you need to learn is how to qoute. but i wont hold my
    > breath on a webtv user.
    >
    > jb books


    Blow Job Booky...its QUOTE, and WebTV...but thats ok...we wont hold our
    breath on an illiterate drunk con artist on his knees in front of a 286
    either..
    Oh..and for longer than you have existed, its been proper to capitilize the
    first work in a sentence, therefore, its The, not the, as you have attempted
    to hammer out in your drunken state of existance.
    CBhvac, Jan 12, 2004
    #17

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. dean
    Replies:
    1
    Views:
    196
  2. Replies:
    3
    Views:
    286
    Bubba
    Dec 30, 2005
  3. jr
    Replies:
    3
    Views:
    154
  4. RedDwarf
    Replies:
    9
    Views:
    129
    Dr. Hardcrab
    Apr 13, 2008
  5. RedDwarf
    Replies:
    3
    Views:
    116
    KJPRO
    Jun 11, 2008
Loading...

Share This Page