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  1. #1
    Join Date
    Dec 2006
    Posts
    6
    I posted earlier concerning my search for a new gas furnace and heat pump to replace my aging furnace and A/C. What advantages do a variable speed furnace offer vs. a 2 stage furnace? Plus are there any differences between Carrier and Trane products?

    I live in Omaha, NE and have a 2 story house with 1600 sq ft above grade + a finished basement. HVAC reps have recommended 90K - 100K BTU furnaces w/ 3 ton heat pumps.

    Thanks for your help!

  2. #2
    Join Date
    May 2002
    Location
    MEDIA PA
    Posts
    1,361

    Two stage

    varible speed is my choice . Both Trane and Carrier are fine (the best) equipmemt . I'm a dealer for both . Carrier infinity system is outstanding .

  3. #3
    Join Date
    Nov 2004
    Location
    Naples, Fla.
    Posts
    1,403
    Max - you're mixing up the equation here:

    Our heating guys can offer some guidance, but break it down like this:

    1) Is a HEAT PUMP more effective in terms of BTU p/ watt than a GAS furnace for my market given KWH cost vs Therm

    2) The term variable speed applies to the BLOWER not the heating source, heat pumps & gas furnaces are available with and w/o variable speed. Variable speed will help keep electric cost down, make up for poorly sized duct work and have some inherent benefit for dehumidification and circulation.

    3) The TWO stage you're speaking of address's the firing rate of the GAS furnace. Two stage offers better temp control, better economy and less temp swing than a ONE stage

    4) In many markets in makes sense to invest in a dual fuel system employing both a HP & GAS where the HP handles the load down to IE: 30 degrees then the GAS takes over - this "balance point" depends on fuel cost and product design

    5) Note - even heat pumps have two stage options --- 1st the best have 2 speed compressors IE: Carrier Infinity, and ALL HP's will cycle conventional strip heat to supplement the demand in low temp applications.


    Have you sought out a competent contractor yet? Have they performed these calcs for you?


  4. #4
    Join Date
    Dec 2006
    Posts
    6

    Frown

    Thanks for your help. I have 4 bids from contractors. Whether they are all competent is a matter of opinion. I believe the heat pump / gas furnace combo makes sense and will save me on natural gas costs during mild fall/winter weather which we have a lot of in Omaha. We also get a fair amount of very cold weather, so I need the furnace.

    Concerning the variable vs dual stage blower, I'm not sure the variable is worth the extra money. Plus I'm concerned that it's too confusing and variable speed blowers are prone to problems.

    You mentioned "calculations". I'm not sure any of the reps performed calculations to support their reccomendations. What kind of calculations should they have done.

    Thanks!

  5. #5
    Join Date
    May 2002
    Location
    MEDIA PA
    Posts
    1,361

    Variable speed

    A variable speed is the blower motor , than run on 3 phase DC . All of the magic is done inside the motor . The saving , is that the V/S motor runs on approx. 1 amp.of electric , were a PSC motor could use up to 9 amps. Put in simple english its like running 1 lamp as to 9 lamps. THe saving is in the cost of energy used.

  6. #6
    Join Date
    Dec 2006
    Location
    IN
    Posts
    59

    Calculations - Variable Speed Furnace

    Max,

    The calculations that these guys are referring to are called load calculations. These calculations determine that exact size of equipment that your home requires. What these guys want you to realize is that if the 4 contractors that you've gotten proposals from didn't spend time measuring your home (measuring square footage, window & door area, ceiling height, attic & sidewall insulation amounts, color of roof, brick or vinyl siding, etc) then they don't really have any evidence to back up their proposals. They may have looked at your current furnace and air conditioner size and basing the proposal off of that, but that's not really providing you a quality service. Moral of the story... get another contractor if none of these four didn't do a load calculation.

    Variable speed furnace - is it worth the extra cost? YES! The variable speed system will enhance the comfort of both the heat pump and furnace and improve the energy efficiency of each as well. In addition, if you've purchased any indoor air quality products (i.e. electronic air cleaner, humidifier, ultra-violet light, etc) the variable speed blower will improve the performance of these products as well.

    Hope this helps,
    -Garrett

  7. #7
    Join Date
    Dec 2006
    Location
    KY
    Posts
    33

    Re: Calculations - Variable Speed Furnace

    Originally posted by gcook
    Max,

    Variable speed furnace - is it worth the extra cost? YES! The variable speed system will enhance the comfort of both the heat pump and furnace and improve the energy efficiency of each as well. In addition, if you've purchased any indoor air quality products (i.e. electronic air cleaner, humidifier, ultra-violet light, etc) the variable speed blower will improve the performance of these products as well.

    Hope this helps,

    How about a 2-stage 80% furnace (with variable speed blower) Vs. a modulating 90+% furnace (also with a variable speed blower) Vs. a 92% single stage furnace with a non-variable blower. All backed by a single stage 13 SEER heat pump. Considering RUUD equipment in Louisville KY.

  8. #8
    Join Date
    Dec 2006
    Posts
    6
    I don't think it gets cold enough in Louisville to warrant a 90% or above furnace. 80% should be good enough for you. I'm still not convinced that a variable speed blower is worth the extra money. I do think the heat pump makes sense. No need to go with anything above the 13 seer, the payback could be longer than the HP will last.

    Good luck!
    Max

  9. #9
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    Originally posted by max_w
    I'm still not convinced that a variable speed blower is worth the extra money.
    What or how can we convince you?

    The pro of what I like about the Variable Speed.

    -Able to run the fan 24/7 for comfort in the home, Temps both upstairs, and basement is the same.

    -With then fan ON, the air flow is very soft and quiet.. don't feel any draft in the winter.

    -Quiet ramping in heating and cooling.. No sudden start up/blast of air.

    -Better control of humidity in A/C mode with a use of dehumidstat.

    -Able to set CFM per ton set up to match the A/C and your region humidity

    -Use less power, with less power, I am able to run the fan and not worry about my meter spining faster.


    These motor been around since late 80's and pretty well proven by now. A good install will make this last just as long or longer than a standard PSC blower motor.

    Only down fall it if you don't get the extneded warranity, it can be expensive to replace... I'd suggest, and I know lot of us here say get the 10 years parts and labor warranity.. It's a good peace of mind for the next 10 years.

  10. #10
    Join Date
    Dec 2006
    Location
    IN
    Posts
    59

    80% vs 90% Modulating vs 90% Single

    Housepoor,

    I live just above you in Indiana and it gets pretty cold in our area just like yours. I really like the idea of the duel fuel heating system that you're considering. Duel fuel gives you the best of both worlds, if the electricity gets out of hand you can always switch back to gas and visa versa.

    If you're going to use a 13 SEER heat pump (hopefully you're looking at a R-410A refrigerant heat pump) then I would choose either the 80% variable or the 90% variable furnace and forget about the single-stage furnace.

    I know that you might be thinking that you don't need the 2-stage or modulating gas heat since your utilizing a heat pump but if you look at the improved efficiency that the variable speed system gives the heat pump, it's worth the cost of the variable speed. When you look at any ARI certified HVAC system, the highest efficiency system always utilizes a variable speed system. I believe the RUDD/RHEEM modulating qualifies for a $200 US Tax Credit (I think it reaches a 95% AFUE).

    If I was you I'd consider how long I would probably live in the home as a basis for choosing between the 80% and 90% variable speed furnaces. If I'm going to be in the home over 7 or 8 years then I'd go with the 90% furnace, if not then the 80%. Either variable speed furnace will provide added indoor comfort to your home.
    -Garrett

  11. #11
    Join Date
    Dec 2006
    Posts
    6
    What is R-410A refrigerant? Does this differ from regular freon?

    Thanks!

  12. #12
    Join Date
    Dec 2006
    Location
    IN
    Posts
    59

    R-410A Refrigerant

    R-410a is an environmental friendly refrigerant that is being phased-in by the government. R-22 can harm the environment and starting in 2010 no new equipment can utilize R-22.

    What this means to homeowners is since R-22 in being phased out the cost of repairs dealing with R-22 will drastically increase. It will be just like the R-12 phase out with the automotive industry - try to get R-12 in today's market and you either pay an arm and a leg for it or its illegal!

    R-22 this past year alone has more than doubled in price and the other factor to consider is equipment quality. R-410a operates at higher pressures and this means that the sturdiness of the equipment has to be able to handle it. If you read most of the manufactures equipment articles, they feel like their R-410a units are the best units they've ever produced.
    -Garrett

  13. #13
    Join Date
    Aug 2006
    Posts
    13
    I live just across the river from Louisville. I just installed a new system about 3 months ago. I'd be glad to give you a contact for a system. I'm a consumer not a dealer, so no sales pitch here, but just from recent experience.

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