Page 1 of 2 12 LastLast
Results 1 to 13 of 14
  1. #1
    Join Date
    Feb 2007
    Location
    Central Illinois
    Posts
    5

    Replacement Furnace blues-My wife's cold blue fingers around my neck

    Hello. I bought an Trane XR90 100k BTU furnace to replace a furnace with a cracked heat exchanger that was 150k btu & 25 years old. I had a few load calcs done & all of them came out to 100k BTU at 90% efficiency to be sufficient.
    The wife is very unhappy with the new furnace as it blows air that is not nearly as warm & takes a longer time to warm up the house when going from cold to warm as we have the thermostat set to cool down at night & during the day when we are gone.
    My question: Is there nothing I can do except adjust the times on the thermostat that the furnace starts up & endure the cold looks from the wife? I am thinking that the cooler air is logical given the size difference of the furnaces.
    Thanks.

  2. #2
    Join Date
    Jan 2007
    Posts
    332
    Blue fingers?--Did you marry a smurf? just kidding. How much do you set back the temperature at night. It may be set back too far and the unit can't recover quick enough. Some digital stats have a smart recovery feature that should compensate for this larger setback by automatically starting earlier. You might check and see if yours has that feature and is activated. Have you checked the supply temps. from all registers and airflow? Dropping from 150 to 100 is a pretty big drop, but hopefully the load calc was done properly. Could be working normal, or could have a problem. Maybe you should call your installer and have them make sure it is working properly.
    Believe none of what you hear and half of what you see.

  3. #3
    Join Date
    Feb 2007
    Location
    Central Illinois
    Posts
    5
    I set it 10 degrees back at night & during the day. It previously took about 45 minutes to go to 72 & now it took over an hour & a half. I will check the temps & ask the installer. The thermostat is not that smart.
    The furnace itself is full heat at all times if I am not mistaken?

  4. #4
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    10Ί is a big setback, try a setback of 5Ί. The 10Ί setback may have actually been costing you more than it was saving you all these years anyway, or at least not saving you enough to be worth putting up with the colder temperature.

    Newer furnaces move a lot more air than the old furnaces used to, so the supply temperature is lower. Your new 100k furnace probably moves a similar amount of air, or even more air, than your old 150k furnace did.
    If more government is the answer, then it's a really stupid question.

  5. #5
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    so what if it takes 2x longer?
    track your btu/degreeday/sqft --

    since I do not have a "smart" t-stat, I brought up temp in steps, 45min ea --

    the larger the temp diff, the less heat loss |gain from the house.
    but, you two have to decide what you are comfortable with!

    as Mark stated, the size of the furn has nothing to do with the supplied air temp -- provided it is working normally, eg: 150k = 100k
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  6. #6
    Join Date
    Mar 2006
    Location
    The South
    Posts
    2,240
    fury

    The XL90 is a 2 stg gas furnace with a conventional blower. Assuming furnace is sized and installed correctly, then I would look at your T-Stat as the culprit. A programmable thermostat with adaptive intelligence feature is required to handle and anticipate your setback and recovery setpoints. With a gas furnace, I would not be concerned with a 10 degree setback assuming you have the correct thermostat and it is functioning correctly. I suspect you are using the wrong stat for your furnace.

    IMO

  7. #7
    Join Date
    Feb 2007
    Location
    Central Illinois
    Posts
    5
    Thanks for all the replies. I do appreciate it.

    It is an XR90 rather than an XL90. (I was going to go with the XV or XL, but we will be moving eventually.)

    I had previously tracked the savings of 5 degree setback vs. 10. 10 had a discernable difference on the bills. I will make changes to the nightime setback & time that it returns to normal.

    It does seem to move a similar or slightly higher amount of air, & it is colder air.

    I am sure we will get used to it & I will be out of the doghouse eventually. I just wanted to verify that this was normal so I could tell her that & ensure that the furnace is operating normally.

  8. #8
    Join Date
    Mar 2006
    Location
    The South
    Posts
    2,240
    fURY

    Sorry, my bad-did not have my glasses on.

    The XR90 is a single stg mid line Trane furnace.

    I still believe your problem lies with your T-Stat. With a sgl stg furnace, you will be throwing out about 92K BTUs and your home should come up to thermostat setting very quickly.

    BTW, what brand/model stat do you have?

  9. #9
    Join Date
    Feb 2007
    Location
    Central Illinois
    Posts
    5
    I believe it is a LUX TX9000 but I could be wrong. I do have an old thermostat to test with.
    Thanks.

  10. #10
    Join Date
    Aug 2002
    Location
    Southold.calm
    Posts
    6,356
    Quote Originally Posted by furyalecto View Post
    I believe it is a LUX TX9000 but I could be wrong. I do have an old thermostat to test with.
    Thanks.
    Please don’t be testing anything. You have a new system with a warranty. Let the installing contractor do any testing.

  11. #11
    Join Date
    Feb 2004
    Posts
    451
    Fury
    Have the installer come back and do a temp. rise on it. As long as it is within the recommended range you can lower the fan speed to increase the supply temp. Coupled with adaptive intelligence, and lowering the setback, you might be able to sleep in the same bed tonight.
    Before you criticize someone, walk a mile in their shoes...that way you are a mile from them and have their shoes

  12. #12
    Join Date
    Jan 2007
    Posts
    115
    more then one way to skin a cat. gas furnaces used to have an adjustable hi limite switch and an adjustable pressure rate to the burner. you can have the gas turned up so that it's closer to the limit, and often times the limit switch can be pushed up a bit (but within the range the mfg will endorse and warrant, and have the installer to the tweaking)

    figure out some area's to attack that reduce the thermal load. That's the same as getting a bigger furnace, but has a payback.

    make sure the humidity level is good, as that affects how temperature "feels"

    push the fan speed up a notch (do you have speed options?) I think you can get a bit more heat off an exhanger w/more air.

  13. #13
    Join Date
    Feb 2006
    Posts
    468

    More air?

    The OP said that the air is already on the cool side relative to the old furnace - speeding up the blower will only make that worse.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event