2-stage heat pump, variable speed furnace
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  1. #1
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    May 2008
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    2-stage heat pump, variable speed furnace

    We live in a 100+ year old, two-story house in Maryland, and have had seven estimates on retrofitting a new system (heat pump, furnace and duct work). We have narrowed our contractors down to two and would like your input on the best system that we have been quoted. More specifically is it worth the extra money to get the 2-stage outside unit and the variable speed inside unit or is one more important than the other? Winter here can be quite chilly and the summer is horribly humid.

    option 1: 16 SEER HP (2-stage) and variable speed oil furnace

    or

    option 2: 14 SEER HP (single stage) and variable speed oil furnace

    Like I said, our house is old and definitely not the most energy efficient, although we will be replacing a few windows and doors once the new system is installed.

    What do you think? Is there going to be a noticeable difference between the two systems in terms of comfort and efficiency? Is it more important to spend the extra money on the inside or outside unit?

    Thanks in advance!

  2. #2
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    I live in Abingdon, Harford County.

    Post the model numbers of the heat pump condenser (outside unit), matching indoor coil, and oil furnace.

    I don't think that 2 stage compressors are worth the extra money, but that's my personal opinion. Variable speed air handler motors can help with humidity removal during mild, humid summer weather.

    Since you are going with a heat pump for your primary heat, you want full btu's. Anotherwords, a 4-ton system should be 48,000 btu's not 44,000. Some system combinations are weak on btu's (this is the reason for posting all model numbers).

    You want 12 EER minimum and 9 HSPF minimum, regardless of SEER, for low operating costs for your new heat pump.

    Adding additional attic insulation, upgrading windows and doors, etc. reduces the heating/cooling load, and pays back every day. Ideally, these improvements should be done before the new system is properly sized by a heat gain/loss calculation.

    Good luck.

  3. #3
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    has your dealer performed a load calculation and if so, did you get a copy in writing and have you had an opportunity to review it with him?

    what is the cost of fuel oil and the efficiency of the oil furnace?

    what is your electric rate and does your utility offer any rate incentive for electric HP heating?

    you normally get a little better comfort and efficiency with a two stg condenser.

    you are aware that heating and cooling a two story home off a single system can be problematic. has your dealer suggested zoning controls or mentioned that two systems will provide better comfort than one system?

    have you analyzed the operating cost of oil vs propane for backup heat?

    just a few ideas to think about.

    IMO

  4. #4
    Join Date
    Mar 2003
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    The price difference can sometimes make the decision for you. I personnally like two speed systems as you don't have full load conditions very often. The lower stage may be able to run for you at part load conditions for longer periods as opposed to one stage cycling. This can help to overcome hot/cold spots caused by poor initial duct design. The variable speed fan does better dehumidiifcation. Really for me its about comfort, and i am willing to sacrifice a bit for better overall comfort. IE, it will cost you more for a higher seer two speed system, but FOR ME its worth it. of course I am not on a tight budget. In most cases where i have seen two speed systems, there really isnt a tremendous energy saving, but homeowners wil tell me about being more comfortable IN EVERY ROOM, instead of knowing that well, in summer you cant use that room or whatever.

  5. #5
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    May 2008
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    Thanks gary_g and tiger dunes.

    Option #1 is Trane HP Model #T4TWX6048A1000A, coil #T4TXCC043AC3HCA, furnace #TTDFIM087A9V5SA. BTUH cooling 48,000, BTUH heating 87,000, 16 SEER, AFUE 82%.

    Option #2 is Lennox HP model #XP14-036-230, furnace #023V2/3-70/90, I don't have a coil model #. AFUE 83%.

    Heating oil is ~ $4/gallon and I don't think that my electric co offers any incentives. We are sticking with oil because we just had a new tank put in last year and it still has oil in it from this past season.

    They did do a load calc, but I have not seen the numbers.

    Since this is going to be a big monetary investment, I am trying to make the best, educated decision that I can. We are meeting with one contractor tonight and the other tomorrow to try and make our final decision. Any final questions I should ask?

  6. #6
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    Jan 2004
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    Lancaster PA
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    If your no going to be tightning up the house anytime soon. A 2 stage OD unit, will provide much better humidity removal then a single stage.
    For a 2 stage to remove moisture right, you need the VS blower.
    2 stage units are comfort units.
    In heating you won't have that cold air feeling you got from your old unit. Same with the cooling if you get 2 stage, you won't have that sudden feeling that heavy air feeling because the humidity is high, because the A/C didn't run long enough on a mild temp high humidity day.

    Guessing they quoted you a Thermopride oil furnace.
    If not, ask them again if the oil furnace has a VS blower, or a Multispeed blower. They are not the same.
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  7. #7
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    1. you need to review load calculation. get it in writing.

    2.without more information, I would not go with a single system without zoning controls. you will be disappointed if you do.

    3.i don't care for the idea of a 4 ton HP on one quote and a three ton on another. one or both dealers are wrong.

    4.oil furnance backup would be my last choice unless you have big pockets and just are unconcerned with operating costs.

    5.i would crunch the numbers on the attached link for fuel comparison calculator. it may surprise you.

    6.what is your electric rate cost/KWH?

    IMO


    http://www.warmair.com/html/fuel_cost_comparisons.htm

  8. #8
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    Quote Originally Posted by 1894House View Post
    Trane HP Model #T4TWX6048A1000A, coil #T4TXCC043AC3HCA, furnace #TTDFIM087A9V5SA. BTUH cooling 48,000, BTUH heating 87,000, 16 SEER, AFUE 82%.
    I would ask Mr Trane to see the ARI (American Refrfigeration Institute) Certification for that combination for the XL16i.

    I find that heat pump condenser and coil with only 1 ARI match, at that was with a different furnace.

    ARI# 3009079. 42,000 btu cooling, 10.4 EER, 13.75 SEER, 38,000 btu heating at 47F, 8.2 HSPF. These numbers suck. Hopefully your numbers are much better than that.

    Good luck.

  9. #9
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    May 2008
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    okay, now I'm thoroughly confused. I'm not real clear on the ARI combination certification. Is there a possibility that the sucky numbers that you listed would somehow be different for me? I'm meeting Mr. Trane tomorrow and Mr. Lennox tonight. What did you think of the Lennox combination that I gave?

    Not that you have all day to explain these things to me, but I would appreciate any info you can give. Basically, you are telling me NOT to go with the Trane combo, right? Should I bother getting a price on the Lennox system with a 16 SEER HP (2-stage) or is the 14 SEER single stage good enough? If I am going to spend the money a better be comfortable!

    Thanks!

  10. #10
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    I live in Montgomery County, so I understand the climate we have. I would go with the 2-stage unit, but make sure it's sized properly. Of course, going with a 2-stage unit gives you a little more leeway as far as sizing goes, but you won't be comfortable without a properly sized system. What tiger dunes said about sizing is right; the fact that one quoted a 3-ton and the other a 4-ton is something to be concerned about. The ARI information is essentially the actualy efficiency and capacity (btu's) that these systems provide, not the "up to xx SEER" stuff. Ask the Trane dealer to see his load calculation and for "proof of efficiency." Need more info on thermostat, ductwork, etc. to accurately compare these quotes. Have you considered a heat pump? They've come a long way and are efficient units for heating and cooling, depending on your electric rates. I know we have some high electric rates around here, but it's the same way with rising fuel prices (from what I hear; I don't actually have fossil fuel). If you went with a properly-sized single-stage system, I would look at the Trane XL15i (4TWX5 series). Good luck with the quotes. Feel free to ask for more input on them (we love to pick apart quotes ).

  11. #11
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    Quote Originally Posted by 1894House View Post
    okay, now I'm thoroughly confused. I'm not real clear on the ARI combination certification. Is there a possibility that the sucky numbers that you listed would somehow be different for me? I'm meeting Mr. Trane tomorrow and Mr. Lennox tonight. What did you think of the Lennox combination that I gave?

    Not that you have all day to explain these things to me, but I would appreciate any info you can give. Basically, you are telling me NOT to go with the Trane combo, right? Should I bother getting a price on the Lennox system with a 16 SEER HP (2-stage) or is the 14 SEER single stage good enough? If I am going to spend the money a better be comfortable!

    Thanks!
    The ARI# means that the components (condenser, indoor coil, and furnace)are an approved match by the American Refrigeration Institute. The certificate, which you can print out once you have the ARI#, lists SEER, EER, HSPF, cooling btu's, and heating btu's at 47F at 17F outside temps for the heat pump system.

    Yes, the sucky numbers could be different than yours. This is why you need the contractor to supply you with the ARI# or ARI certificate. If there is no ARI#, then "buyer beware". I am NOT telling you to NOT go with the Trane, I am telling you that you need an ARI approved combo to get the efficiency ratings and performance that you are being quoted.

    I can't do anything for Lennox because the coil model number is not stated.

    You should get as many system quotes as you can. If purchase price is not an issue, then go with the 2 stage system. If purchase price is an issue, a single stage system (14 or 15 SEER) should do fine as long as it is properly sized and installed.

    Good luck.

  12. #12
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    May 2008
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    thanks guys, you've been really helpful. In reference to zoning controls, are they available for heat pumps and oil furnaces? I've spent all this time getting quotes on oil and now I am starting to wonder if it would make more sense to go with LP (natural gas isn't available here). Is there a big cost difference between the two types of furnace? Is installing the propane tank a significant expense? Are the zoning controls real pricey? I'm making it sound like I am overly concerned with the initial cost, and it is a concern, but I am also very interested in getting an energy efficient and comfortable system.

  13. #13
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    Don't unnecessarily jump right into zoning. It would be good to have ductwork that is "zoning-ready," but with a two-stage system with a variable-speed blower running 24/7, you may be fine--so I'd give it a shot first. I don't have serious issues with one system without zoning in my house (2 stories). A lot of it has to do with air distribution and proper system sizing, which unfortunately is ignored all too often. Do you have ductwork already? The upstairs is inevitably going to be warmer in the summer and winter, but it may not be too bothersome. It varies by situation, though. I leave my thermostat at 72* for cooling usually, and my home has plenty of shade; I'm not sure about your situation.

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