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  1. #14
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,929
    Quote Originally Posted by a/c-harris View Post
    Since I live in dallas we dont get below 30 degrees very often. So anything above 30 degrees the stat is set up to not allow electric heat to come on. This is common practice, I dont know why everyone in arguing.
    If you lived where it got cold in the winter, you would know why.
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  2. #15
    Join Date
    Jul 2007
    Location
    Manchaster, NJ
    Posts
    18
    looks like it is running ok
    1st stage is going to raise the temp only to a certain point when it cannot keep up. The stat then brings it to 2nd stage and then the strip heaters and ten back down to 1st stage to try to mantain set point temp
    being the temp is in the 20:s and the system is mantaining 68 and you are comfortable you doing good

    last thing you want imo is to rely on those electric strip heaters \ you bill will go through the roof

  3. #16
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    I agree, there is nothing wrong with your system.. That is normal, that's the ideal behind a two stage system = long run time for comfort!

    If the t-stat's 2nd stage can't keep up, then the Aux will kick in to help out and goes back to 2nd..... 1st.. as needed.

    So, sit back and enjoy the new system and knowing you are saving money by running the heat pump steady vs having the electric heat cycling the t-stat on and off.

    I have a two stage gas heat, and when we are 0˚F or colder, the 1st stage pretty much runs none stop, and cycles 2nd stage every now and then.

  4. #17
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    2,006
    Possible decription of the perfect heating system: One that puts exactly the amount of btu's into the structure that are being lost and runs 100% of the time that the outdoor temperature is such that setpoint can't be maintained without the addition of btu's.

    Why you ask.........

    Well it's like this....... if the area near the floor is getting cold the occupants will be uncomfortable (cold air sinks). This happens at different rates in direct proportion to the temperature difference between what you're trying to maintain in the home and what it is outside. The rate it happens is a result of the amount of btu's that are leaving the structure. To replace these in the exact amount that they're leaving results in PERFECT comfort. And IMO the ultimate in efficiency.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  5. #18
    Join Date
    Nov 2004
    Location
    Austin, TX
    Posts
    876
    Your two stage heat pump is doing exactly as it was designed.
    The second stage is coming on when the first stage doesn't keep up.
    The first stage runs almost all the time to match the heat loss from the home.
    Total wear and energy consumption is very low because the continuous run time reduces the amount of startup wear and current surge .
    Longer run times reduce air stratification within the home.

    Still the thought of the system running constantly drives some people nuts.
    I am for doing good to the poor, but...I think the best way of doing good to the poor, is not making them easy in poverty, but leading or driving them out of it. I observed...that the more public provisions were made for the poor, the less they provided for themselves, and of course became poorer. And, on the contrary, the less was done for them, the more they did for themselves, and became richer.
    ― Benjamin Franklin

  6. #19
    Join Date
    Jan 2007
    Location
    Arkansas NWA
    Posts
    33

    Not Maintaining

    In the origianal post he said it is not reaching setpoint! (unless I miss read) If I did soooooo sorry!

  7. #20
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,929
    He didn't say it wasn't maintaining set temp. He said it doesn't shut off.
    Its maintaining his set point (68*), but is running constantly when the OD temp is below 20*. And he thought it should shut off.
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  8. #21
    Join Date
    Jan 2007
    Location
    Arkansas NWA
    Posts
    33
    If it is reaching desired temp shouldnt the unit cycle off, or does the compressor (1st stage) run continuosly? If this is the case than I just learned something about this system.
    Thanks

  9. #22
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,929
    The stat is keeping it on, because the stat is not set up to completely satisfy the heat demand on second stage when its below first stage balance point ( a couple tenth of a degree).
    Its a comfort feature that can be disabled. But why buy a comfort system and then defeat its ability.


    Some 2 stage heat pumps have a lock out temp that they will automatically go to second stage heat pump after the OD temp gets to that lock out temp.
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  10. #23
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Quote Originally Posted by FSHnFRK View Post
    If it is reaching desired temp shouldnt the unit cycle off, or does the compressor (1st stage) run continuosly? If this is the case than I just learned something about this system.
    Thanks
    The thermostat utilizes the available stages of heat to maintain the set temperature as closely as it can, without overshooting.

    If the outdoor temperature is blow the balance point, the heat pump, or first stage of a multistage heat pump, will run continuously.
    The thermostat will cycle 2nd stage of the heat pump, and the electric supplemental heat on and off as needed to maintain the set temperature, but won't cycle the system completely off unless it starts to overshoot the set temperature.

    The idea is to do as much of the heating as possible with the heat pump, since it costs less per BTU of heat than straight electric heat, even down well below 0º outside.
    Cycling the heat pump off when it doesn't have to be cycled off also reduces the systems efficiency a lot.

    It is also a more comfortable way to operate the system, since you don't get the constant swing of the house heating up, then cooling down.
    If more government is the answer, then it's a really stupid question.

  11. #24
    Join Date
    Jan 2007
    Location
    Sioux Falls, SD
    Posts
    9

    It is also a more comfortable way to operate the system!!

    Sorry I didn't log on sooner as I see I've missed a lot of conversation about this subject.

    Benny makes some good points about how the system was set up to run and how his 5 stage heat pump works. Just one problem for most people, myself included. Is the system efficient? And is it comfortable? For me there is a fine line somewhere with any all electric heat pump system where I give up on saving a few pennies and opt for some comfort.

    It's like be married, meaning we all have to compromise once in awhile. I personally think all HP systems should have a plenum sensor set to monitor the discharge temperature to make sure we maintain a certain temp which the customer can feel comfortable with. Someone also mentioned schooling the customer on how a HP system works, which should be SOP for every installer worth his salt. The problem is everyone (especially older homeowners) have a different idea of what is comfortable to them. Hence we could argue about this until the cows come home.

    I'm just happy to see some interest in heat pumps. They are a great alternative heat source and very competitive if your electric rates are reasonable.


    Blue skies,
    Killowattdiver

  12. #25
    Join Date
    Apr 2004
    Posts
    7,680
    Blue Skies? Sounds like a skydiver. Ol' DocHoliday used to punch clouds but gave it up about 8 years ago.

  13. #26
    Join Date
    May 2007
    Location
    Upstate SC
    Posts
    188
    I could certainly see that, Firecontrol. Nicely put. Like you said, the rate of heat loss from inside to outside is directly propertional to the temperature difference between the inside and outside. (heat loss = overall heat transfer coefficient times surface area of your walls&ceilings times the difference in temps between inside and outside (q = UA(T1-T2) ).

    So if a tstat overshoots and warms your house 1-2 degrees warmer than your setting, your rate of heat loss is greater i.e. you're losing more BTUs during that time of overshot than you would lose if the setting was dead on. Thus you wasted the energy you put in the house from the setpoint to the point the system stopped at the overshot temp.
    Which from my understanding is why variable speed air handlers/blowers and multi-stage HPs and furnaces came about anyway... to try to eliminate the under and overshooting of your setpoint from sharp temperature changes, to softer, more attenuated temp changes. Minimize the area under the curve between the setpoint temp and actual temp on a graph of actual Ts versus setpoint. Anything above the setpoint you're wasting heat, anything below the setpoint you're not comfortable.

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