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  1. #1
    Join Date
    Mar 2010
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    5

    Modulating Furnace vs. 2 stage

    I am considering updating a 20 year old Goodman single stage furnace to a high efficiency Trane or Rheem furnace. I have a two story 2600 sq ft house in southeastern Wisconsin with new windows and R-30 insulation. In looking at high efficiency furnaces, I can get either a two stage or modulating furnace. I have heard that modulating furnaces sometimes do not heat the upper rooms as well at the lower heat settings which negates some of the advantages. I have heard the two stage furnaces do not have the problem. Is this true? How can I find out without a costly install only to discover my upper floors do not have enough heat? Any thoughts on Rheem vs. Trane?

  2. #2
    Join Date
    Feb 2007
    Posts
    999
    Quote Originally Posted by tftay01 View Post
    I am considering updating a 20 year old Goodman single stage furnace to a high efficiency Trane or Rheem furnace. I have a two story 2600 sq ft house in southeastern Wisconsin with new windows and R-30 insulation. In looking at high efficiency furnaces, I can get either a two stage or modulating furnace. I have heard that modulating furnaces sometimes do not heat the upper rooms as well at the lower heat settings which negates some of the advantages. I have heard the two stage furnaces do not have the problem. Is this true? How can I find out without a costly install only to discover my upper floors do not have enough heat? Any thoughts on Rheem vs. Trane?
    I am going through my 2nd winter with my Rheem Mod. Previously, I had an oversized beast (was 20 years old). When it ran, the the air flow was strong and it was noisy as hell.

    That being said, I was always cold (especially on the 2nd floor) and since the furnace would short-cycle, I couldn't wait for the next cycle to begin.

    Now, after morning recovery, the heat runs most of the time and I have to put my hand to the register to feel the heat, barely trickling out.

    Needless to say, it is quite comfortable. Haven't had to use the space heater in the (2nd floor) bedroom.

    If the unit is sized correctly, it will run long cycles (at reduced input) and you should be comfortable.

    I say that, as you need to have your ductwork evaluated and corrections made if necessary. Mine would not win any blue ribbons, but with minor changes, I am much more comfortable at greatly reduced airflow (quiet).

    One note: I don't believe the Mod qualifies for the $1500 tax credit, as it is less than 95 AFUE.

    Amp

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,168
    Our customers love Rheem's Mod, been selling for 10+ years. But alas, Amp is right - doesn't qualify for the full tax credit til the new line comes out this fall. So I'd look at the RGRM 2 stage or if you are into Trane, the XV95 or I think their Mod is XC95.

  4. #4
    Join Date
    Mar 2010
    Posts
    5
    Thanks! So it looks like if properly sized, I should not have a problem. Actually Rheem is coming out with a 95+ modulating furnace this month that qualifies, but Trane has one now that does qualify. Should I wait for the Rheem?

  5. #5
    Join Date
    Jul 2006
    Posts
    6,528
    Quote Originally Posted by tftay01 View Post
    Thanks! So it looks like if properly sized, I should not have a problem. Actually Rheem is coming out with a 95+ modulating furnace this month that qualifies, but Trane has one now that does qualify. Should I wait for the Rheem?
    I would.
    You sure are cocky for a starving pilgrim.

  6. #6
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,119
    Quote Originally Posted by tftay01 View Post
    Thanks! So it looks like if properly sized, I should not have a problem. Actually Rheem is coming out with a 95+ modulating furnace this month that qualifies, but Trane has one now that does qualify. Should I wait for the Rheem?
    Rheem or Trane either one.

    Make sure contractor checks all ductwork for proper air flow this is very important for your comfort, esp 2nd floor.

    We sell Am Std and the first mod we put in I had to go back because their HP wasn't defrosting and they had to run on em heat until I went back with the new part. The first thing Homeowner asked me when I went back; "What has been heating my house? The furnace hasn't come on once since you diagnosed the HP." The temp had been 20 to 30 and the furnace was their only source of heat. I told him just the furnace because it was in em heat. Needless to say he was quite impressed that he hadn't heard it. He also told me their house has never been this comfortable.
    Last edited by Chuck; 03-10-2010 at 05:21 PM. Reason: clarification

  7. #7
    Join Date
    Mar 2010
    Posts
    5
    Is the modulating furnace worth the extra cost - around $? seems like the two stage would give a nice improvement in comfort over my current single stage.
    Last edited by beenthere; 03-10-2010 at 08:27 PM. Reason: price

  8. #8
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,168
    Didn't know Rheem's mod would be out this soon.

    With A-S/Trane, make sure they are including the communicating control and not using a single stage stat. They are pricey but do a lot for the furnace including dehumidification control in cooling season.

    2 stage is nice, modulating is amazing.

  9. #9
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,837
    Multi-staging and modulation are huge for comfort. Is it worth the extra money to be comfortable for the next 15-20 years? Probably not if you bought a Yugo when they were around. Would you pay $1.00 per day to get a system that provides continuous heat on cold days, rather than on-off-on-off? If yes then you've answered your own question. However one other issue comes up as well. Did anyone do a load analysis on your house or are they just going by the old unit size? I sold a furnace today to a gentlman who had a 150,000 Btu input 120,000 Btu output gas furnace. The load analysis revealed a need for 41,409 Btu's at -2 OAT. Talk about over sizing!! The existing furnace is working and he did purchase a modulating furnace. His comfort level will go through the roof with the new furnace compared to the old. And yes he has AC and it's a 2-ton unit and it will be like night and day for him when the furnace is properly sized for the house AND for the AC system. The only question is, how many 'steps' does one need to get comfort?

    The DOE data says that the top 20% of a gas furnace is only used 2% of the time for a properly sized furnace. So that begs the question, does one really need steps 4, 5 or 6? Just a question to ponder.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  10. #10
    Join Date
    Mar 2010
    Posts
    5
    Actually, none of the contractors did a manual J calculation, but the Rheem guy spent more time looking at my ductwork and room sizes. He actually recommended a slightly smaller furnace - a 90,000 btu input versus 100,000 for the trane and carrier (my current Goodman 92 is a 100,000 btu). I downloaded a program that performs the calculation in more detail (not a manual J, however). It asked for room sizes, window surface area, insulation thickness, etc. that seemed to do a better analysis than the typical internet based calculation where you just put in your square footage. It came up with an 84,000 btu heat load. Interestingly, the Rheem guy is pushing the two stage because in his experience (which is about 30 years in business), two story houses have problems with air flow to the second story. He has put in sensors in the second story to counteract this problem. The result is the furnace modulates somewhat higher than normal negating some of the advantage. I realize he may be pushing two stage because Rheem has no modulating furnace that qualifies for the tax credit, although he did quote me on a York modulating furnace. He, however, seems to spend more time answering my questions than the others.

    Still uncertain if the modulating is worth the extra cost - about $ extra particularly if two stage provides a big improvement in comfort.
    Last edited by beenthere; 03-11-2010 at 12:20 PM. Reason: Removed price difference

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,074
    I removed the price difference from your post.

    No pricing questions. Please read site rules, thank you.
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  12. #12
    Join Date
    Mar 2010
    Posts
    5
    Sorry about the price mention. I have read the forum rules now and will abide by them.

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