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  1. #1
    iowa cool cat Guest


    I have a 15 year old Lennox 78% efficient furnace that I need to replace. The heat exchanger has been replaced once and we have noticed a boom when the gas draws in to ignite. We have the furnace serviced every Fall and A/C every Spring. It seems like small things are going wrong with it and we have had enough.
    I contacted two reputable local contractors to give us a bid on a new furnace; 80% and 92% efficiency units for comparison purposes. We are leaning towards a Ruud 60,000 BTU 92% efficiency two-stage furnace (model UGRK 06)after talking to the contractors and researching on our own.
    We live in East/Cenrtal Iowa and it appears that the 92% is the way to go.
    Does anyone have opinions on the Ruud 92%? What about a 2 stage variable speed blower Ruud model?

    The real purpose of posting this is that one contractor seemed to think that our duct work is fine that exists and the other one has issues with the duct work. A lot of what he said seemed to make sense, but I do have some reservations and want to make certain. I will list his concerns below.

    (1) The air intake plenum necks down at the top to a dimension of 6" X 24". This is the only cold air return to the furnace. (our home is 975 Square foot (on the main level) ranch style home. We are heating the basement as we have a bathroom and exercise area down there. The contractor feels that we need more area for the intake and proposes adding another intake in the basement. He said the current furnace is starving for air with the current set up.

    (2) He recommends adding a 6" Trion air filter. We have pets and my wife has allegies. I have looked into that previously and think that is a good idea. The first contractor said what we have now is fine (1" x 25" 3M allergen filter).
    Is the Trion a real deal as far as minimizing the cat hair and dust?

    (3) The transition from the furnace to the main heating plenum goes straight up into the bottom of the phlenum and obviously then hits the top of the phlenum before the heated air flows out to the ducts. The contractor recommend putting a 45 degree lead in on each side of the transition so it can branch to the phlenum with less turbulance.
    Is this a real issue?

    (4) The heating ducts that branch off from the main plenum are in question also. One runs straight out the end of the phlenum. The contractor suggests moving the duct to the side and extending the phlenum a couple of feet past the duct to minmize turbulance. The other end of the phlenum has 2 ducts right at the end and he feels that the phlemun should be extended a couple of feet there as well.
    What do you think?

    Our current furnace does make a lot of noise. My wife has complained about that since it was new 15 years ago. All of the duct work for the intake was redone then and it really was not a stellar job as far as workmanship in my opinion or hers. The contractor suggesting the duct reworking saw the unit and said immediately that the furnace needed a lot more intake than that to be efficient. He also explained that a lack of intake air flow could cause premature failure of a heat exchanger and other issues one of which was noisier than it should be. That grabbed my attention as we had not told him that the heat exchanger had been replaced 5 years ago, that it was noisy than the old one and that it cycled on and off a lot in the winter.

    Please let me know what you think about any or all of these issues. I am always looking for all of the facts prior to making a decision that will impact us for the next 20 years or so. Your assistance is greatly appreciated.

    Thank you,

    Iowa Cool Cat

  2. #2
    Join Date
    May 2000
    Indianapolis, IN, USA
    Post Likes
    The UGRK is a great furnace. Reliable, quiet, easy to maintain. No 2 stage variable speed but the top Ruud furnace is the infamous Modulator. Intead of 2 stages, it continuously varies fire from 40% to 100% and the blower is on temp sensors to maintain hot air throughout the whole firing range. If you have the budget for it, no furnace compares in heating comfort.

    1. 24x6 is about 1/2 the air you need so something must be done.

    2. 3M filters are great but plug up quickly blocking airflow. Their top model especially so. The Trion lets you get 9 to 12 months without media change. If you are prompt at changing the 3M monthly or every other month, stay with it. Most of our customers aren't.

    3. May not be worth the cost of doing the work but he has a point.

    4. Same as above. If done right, runs don't come off the end of a duct but hard to say if the bucks it will take to change is that big of a deal. Getting the proper amount of return is most critical.

    Undersized duct system will make even the quietest furnace noisy. On low fire, the blower can be set on the lowest speed and with a proper duct system, be very quiet. It does bump up a couple notches for high fire but still if ducting is right, be a quiet system. I put a single stage 06 Ruud furnace next door last fall. Quiet was the first comment I got from my friends.

  3. #3
    Join Date
    Oct 2003
    34.8n 102.4w
    Post Likes
    Sounds like the second guy wants your new system to work.Go with him.... JMHO.
    Life goes on long after the thrill of living is gone.

  4. #4
    Join Date
    Mar 2005
    leland nc
    Post Likes
    sounds like all of your conserns have already been answered
    the guy that was there and made all of the recamendations seems to know what he is saying and you say the sme thing
    since you are going to replace this unit now is the time to solve all of the complaints you had with the old unit and have it right. the rudd unit is a good unit and if installed correctly will give you many years of comfort
    if he can see the points of concern before you even tell him about then and recomends how the solve them well why go the expense and have the same problems with the new as with the old
    have him come back ask him qestions tell him all of you conserns make sure you understand everything you are beening told and go with the one that makes you feel the most comfortable

  5. #5
    Join Date
    Nov 2003
    Post Likes
    It sounds like everything has been addresses but I will add that the 3M filters are great at ruining heat exchangers if not changed every couple of weeks. The Trion is a major improvement.

    Yes the return needs to be improved, this will help with your airflow noise problems.

    adding the 45's where the plenum connects to the trunks will also help reduce noise.

    Never run a branch off the end of a trunk.

  6. #6
    iowa cool cat Guest

    Cool Thanks for the input guys


    Thanks for all of your input on the furnace selection and related issues. You have been extremely helpful. This is an awesome forum for those who are going through the process of finding information like I was. I wish there was a forum like this for more things to confirm or shoot holes in what I am thinking.
    Keep up the good work!!!!!!

    Iowa Cool Cat

  7. #7
    Join Date
    Apr 2004
    Post Likes
    Might want to get a quote on the Ruud mod 90 too, if you are going to upgrade, this is an outstanding option. Do a search in here for it or go to and see what I mean.

    BTW, I have the GRK 2 stage in my home, and love it. (even though it is aux for my HP)

  8. #8
    Join Date
    Apr 2003
    Post Likes
    air return 6 x 24 is about 700 cfm. Of course I'm a Trane fan ..... but it seems to me that Ruud is ok... Seems they over air them but their ok.... Yes do something with that return air... and make sure your supply air is enough too.

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