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  1. #1

    Another question about heat pumps

    Last week I asked for advice about whether to go with a gas furnace or a heat pump and most said go with the heat pump. I have read a few threads about heat pumps and extreme cold temps and I'm confused. If I get a heat pump, would it be better to go with electric heat strips or a backup gas furnace. I live in central Nebraska and the temps can get into the double digits below zero. I want the most efficiency as far as cost, but my primary interest is in staying warm.
    I have gotten an estimate from a Lennox dealer for an XP14-036-230 heat pump with heat strips. Will this be sufficient to warm my, two-story with basement, 2400 square foot home? Any comments will be appreciated. Thanks.

    Neal

  2. #2
    Join Date
    Jan 2003
    Location
    Olathe Kansas
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    246
    You'll be needing some backup heat for sure at those temps. Usually strip heat is is sized so it can heat home entirely by itself if needed. Talk to your dealer about these concerns. Couldn't tell you if elec. backup will be cheaper than nat. gas in your area. Might want to ask about that option too. Weigh your options before you pull the trigger.

  3. #3
    Join Date
    Dec 2007
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    Southern, CA
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    520
    You'll need backup of some kind, as heat pumps poop out I hear when it gets 45 to 50 and below. Cause there's no heat out there to bring inside. From what I've read here, SoCal is bass ackwards from most of the country. Here they charge up the wazoo for electric, and natural gas is real cheap. And anybody here using a HP is a fool. I've never paid more than $50 a month for gas, but know people who've had a $400+ a month strip heat tab. A little less with a HP. Since prices seem to change daily, your best resource for info may be a crystal ball. Go with whats cheapest for backup, in your area it might be strip heat.

  4. #4
    Join Date
    Jan 2004
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    Heat pumps provide plenty of heat at temps below 40°F.

    OP: Whats your electric rate, and whats your gas rate.(Delivered, all taxes included).
    Also, was a load calc done to know how much heat you need.
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  5. #5
    Join Date
    Aug 2008
    Location
    Indianapolis
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    41
    You'll need backup of some kind, as heat pumps poop out I hear when it gets 45 to 50 and below. Cause there's no heat out there to bring inside

    there is heat in the outdoor air down well below 30 and below 0 and below -30 but there is point where you spen more money to get the heat than you gain and that is usual around 30 outside

  6. #6
    In my previous post, I gave the costs for gas and electric rates in my area. One member calculated that gas @ 80% eff. would cost $17.11 per million btus, gas @ 90% eff. would cost $15.21 and electricity would cost $6.31 per million btus, so he recommended the HP. I'm certain that I will need backup heat, but whether gas or electric is more efficient. I want to be warm.

    Will the electric heat strips provide enough heat if the temps are below zero?

  7. #7
    Join Date
    Jul 2004
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    Massachusetts
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    Quote Originally Posted by Coolmaniac View Post
    You'll need backup of some kind, as heat pumps poop out I hear when it gets 45 to 50 and below. Cause there's no heat out there to bring inside. From what I've read here, SoCal is bass ackwards from most of the country. Here they charge up the wazoo for electric, and natural gas is real cheap. And anybody here using a HP is a fool. I've never paid more than $50 a month for gas, but know people who've had a $400+ a month strip heat tab. A little less with a HP. Since prices seem to change daily, your best resource for info may be a crystal ball. Go with whats cheapest for backup, in your area it might be strip heat.
    This is a joke answer, right? 80% of the heat in the air is still available at zero-degrees. Absolute zero is well below that you might remember from thermodynamics class, -459*F. So a HP can pick up a lot of heat at temps. below 25 or 30. Whether it has sufficient capacity to heat the space is subject to proper sizing and installation. And I seriously doubt that the amount of gas you burn in So. California would heat a Nebraska home for 24-hours in the dead of winter.

    Using a HP alone in Nebraska for the dead of winter is probably not a good idea, unless it's a geo-thermal properly installed. Otherwise I'd recommend a dual-fuel system, whereby you take advantage of the HP during the milder days and use the fossil fuel system for the coldest weather. You need to do your homework as to the efficiency of gas versus electric heat in your area. You can choose from natural gas, if available, propane gas, fuel oil if available or electric resistance heat. A good HVAC company that does dual fuel systems will be able to help you with that, so your job is to find a good company. Start that process by polling by telephone each company in the phone book and accept for bids only those companies that answer the question appropriately. The question is, "How do you size a furnace or air conditioning system for a home?" The only acceptable answers are those that refer to a heat gain/loss analysis. All other methods, by experience, by square footage or similar should be rejected out of hand.
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  8. #8
    Join Date
    Jan 2004
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    Quote Originally Posted by mountainrivers View Post
    Will the electric heat strips provide enough heat if the temps are below zero?
    Electric strip heaters can provide as much heat as gas, with the right air handler.

    How much heat do you need in BTUs.
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  9. #9
    Join Date
    Jul 2008
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    Poestenkill, NY
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    This comes down to fuel cost and equipment cost. That's it.

    Any type of system can be sized to match the heat load of the building. HP with electric resistance back-up or HP with natural gas back-up seem to be your two most obvious choices. You need to do the math to determine which back-up fuel is cheaper to burn, resistance electricity or natural gas. In most areas, gas is a no-brainer. By far. I think your rates were unique IIRC, so you need to do the math with your rates.

    Further, I suspect the capital cost of an all electric system would be cheaper than the capital cost of dual fuel, obviously varying your pay back time. Your electric service size might also come into play if you go wuth electric resistance back-up, changing the service entrance is expensive if that were necessary.

  10. #10
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    Jul 2008
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    Poestenkill, NY
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    Quote Originally Posted by Coolmaniac View Post
    You'll need backup of some kind, as heat pumps poop out I hear when it gets 45 to 50 and below. Cause there's no heat out there to bring inside.

    Yikes.

  11. #11
    Join Date
    Nov 2007
    Location
    Olympia, Wash.
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    Quote Originally Posted by Coolmaniac View Post
    You'll need backup of some kind, as heat pumps poop out I hear when it gets 45 to 50 and below. Cause there's no heat out there to bring inside. :
    That is simply wrong. I'm not a professional but there have been professional folks on this site who will tell you otherwise. Personally, my natural gas furnace backup heat doesn't come on until the outside temp drops to 25 degrees.

    My balance point is 17 degrees (the cost where my furnace and heat pump cost the same to run based on my energy rates) and I'm thinking of lowering the set point to 20. However, I made some other changes to the house and want to see how the KWH compare from 2007 to 2008. My house stayed nice and warm at 70 degrees last year. Others will tell you the same experience.

    Factories seem to have the default thermostat settings at 40 degrees for backup heat. You set the thing for your area and your electricity/gas costs and your system performance.
    "Therefore, since we have been justified through faith, we have peace through our Lord Jesus Christ.." (Romans 5:1)

  12. #12
    Join Date
    Nov 2004
    Location
    NJ
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    1,195
    I know a couple of guys who live in Ne. They have co-op's that charge amazing elec rates in the < $.03 KW range while gas costs in the > $15 per 1000 CF. Heat pumps are way cheaper and even elec resistance can cheaper to operate.

    I just did our local rates on Friday and we're at $1.70 for 1000 CF for nat gas and elec is at $.195 a KW. That should give you an idea of how cheap the elec can be in some areas.
    Ed J

  13. #13
    Join Date
    Jun 2007
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    Quote Originally Posted by mountainrivers View Post
    In my previous post, I gave the costs for gas and electric rates in my area. One member calculated that gas @ 80% eff. would cost $17.11 per million btus, gas @ 90% eff. would cost $15.21 and electricity would cost $6.31 per million btus, so he recommended the HP. I'm certain that I will need backup heat, but whether gas or electric is more efficient. I want to be warm.

    Will the electric heat strips provide enough heat if the temps are below zero?
    That member was probably me, and I believe I used a C.O.P. of 3.25 (at 35F ambient) to calculate the cost of 1 million btu's of heat for the heat pump.

    So, electric resistance heat would be 3.25 times the operating cost of the heat pump:
    $6.31 x 3.25 = $20.52 for 1 million btu's of electric resistance which is more expensive than the 80% efficient gas ($17.11) and 90% efficient gas ($15.21).

    If I were you, I would probably consider a dual-fuel system (heat pump plus gas furnace auxillary). This way, if the price of either gas or electricity swings high, you can choose the lower cost heating fuel. Choices are a good thing.

    Take care.

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