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  1. #1

    Question Should we buy a new furnace? AC?

    We live in Michigan and our 2000 sq. ft. ranch was built in 1987. Our natural gas, forced air furnace is at the north end of our basement so that end of the house (bedrooms) is always warmer than the south end (living room, kitchen). We never run our furnace higher than 68 but we have higher than average gas bills. Similarly, we never run our AC lower than 80 but our electric bill is almost twice that of our neighbors who run their AC at 72. We had insulation added, our duct work taped, and re-caulked our windows. It doesn't seem to have helped.

    Our current furnace: Williamson Gasaver, 120000 BTU, 24 years old. This is a 2 stage furnace that was rewired to run at high only. I believe it could be switched back to 2 stage but we'd need a special thermostat.

    Our current AC: Bryant, 2.5 ton, up to 13 seer, 15 years old. It struggles to keep the house at 80 when the outside temp is in the 90's.

    When we moved in, 8 years ago, we figured we'd soon need to replace the furnace but it just keeps on going. We have $900 remaining of the tax credit so it seems like a good time to consider a new furnace. We've received 3 quotes (Amana, Bryant & Lennox). All three companies recommend a 95+% efficiency furnace so we can use our remaining tax credit. They also recommend 2 stage and variable speed. We were just looking for a new furnace but they all say our AC isn't big enough and recommend we replace it.

    OK folks, we'd REALLY appreciate some input:

    *Should we keep our current furnace and look into switching it back to a 2 stage furnace?
    *Should we forget about the tax credit and get estimates for less expensive furnaces that are lower than 95% efficiency?
    *Can a 2 stage and/or variable speed furnace help solve the problem of it being colder at the south end of our house?
    *Can a new furnace improve the performance of our current AC?

    Thanks in advance!

  2. #2
    Join Date
    Jul 2006
    Posts
    6,310
    Your furnace is probably older than 20 years and is probably more like 60 percent efficient.
    All my customers love the variable speed two stage or mod furnaces, hold on we have several people here from Michigan who will know more about your needs and tax incentives, federal and State.
    You sure are cocky for a starving pilgrim.

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,396
    *Should we keep our current furnace and look into switching it back to a 2 stage furnace?
    *Should we forget about the tax credit and get estimates for less expensive furnaces that are lower than 95% efficiency?
    *Can a 2 stage and/or variable speed furnace help solve the problem of it being colder at the south end of our house?
    *Can a new furnace improve the performance of our current AC?
    1. For efficiency reasons, I'd replace.

    2. No, take advantage and get the 95%

    3. Maybe. But too many claim these new furnaces will solve uneven heating but they can't overcome duct issues. Had a call yesterday that the guy's house isn't any more comfortable despite what our salesman told him.

    4. Maybe. Depends upon what kind of air the old Willie is moving. But likely not. 2.5 ton for 2000 sq ft in Michican doesn't sound too out of line. Could be your old unit isn't up to snuff. A good dealer would run a load calc and see what size A/C you need. Before anyone says go 3 ton, better make sure your duct system can hold the extra airflow needed. Also, too many like to oversize furnaces which isn't good either.

  4. #4
    Join Date
    Nov 2010
    Location
    Andover Kansas
    Posts
    2,115
    I agree with baldloonie, you should take advantage of the tax credit now before it is too late...and have a load calc done on your house to size the system corectly, then you will know if your current system is too small to handle the heat load in the summer.

    Your system is towards the end of it's average lifespan, so now is the time to replace it.

    With your furnace at one end of your house and bedrooms at the other, the previous owner may have not been satisfied with the furnace while it was on 1st stage and may be the reason it was wired to run on 2nd stage all the time.

    Some ductowrk issues can be overcome depending on the house and the originall installation, often by just adjusting the registers. I would recommend having a trained pro that uses an airflow balometer to check out the airflow in your house.

  5. #5
    Lots of good info! Thank you for taking the time to reply.

    These companies leave me feeling like I'm from another planet when I ask about doing load calcs, etc. They imply that they know what we need based on their past experience. Do you think that's just standard in our market (SE Michigan)?

    How picky can we be and still expected to have it installed by year end for the tax credit?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,770
    Try to find a company that will do a load calc. Your 120,000 BTU may be grossly over sized. And your duct under sized for it. This will often cause the closest rooms to be warm/hot, and the furtherest rooms to be cool/cold in the winter. Along with higher heating bills.

    A 2.5 ton A/C on a large furnace like that. Can often have problems from too much air flow. hard to cool the air if too much is going through the coil.

    A correctly sized 2 stage will help to even out room temps in the house(its not a cure all though). A 2 stage being controlled by the thermostat, will give you long on times at a reduced air flow. Which helps even out room temps by not "forcing" a lot of air out of the supplies that are the closest to the furnace. Allowing the other rooms to get more air. But, if they just put back in the same size as you have now, and you only needs an 80,000 BTU 95%, your not going to get the comfort you paid for. And your room temps will still vary a lot form one end of the house to the other.
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  7. #7
    Hello beenthere! I see you're in PA. My sister lives there and we vacation there often. Beautiful state!!

    Yes, we were told that the current 120,000 BTU furnace is over sized because when it was installed (1980's) "the bigger the better" was a common Philosophy.

    The quotes we received were for 70,000 or 80,000 BTU furnaces. Does that sound in the ballpark for a 2000 sq. ft. ranch in Michigan?

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,770
    Closer then a 120,000 does.

    Weather a 60,00 is enough can't say. It may be, and the 80,000 would be over sized.

    A load calc is the best way to know.
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  9. #9
    Im with the other guys on this. If you are concerned with the amount of money you are spending to heat or cool your home, you really should think about upgrading in AFUE. As far as hot and cold spots within your home, you may want to think about zoning. Explain your concerns to your local tech, and they should be able to provide you with some solutions.

  10. #10
    Don't buy any system from anybody that hasn't done, or won't do prior to equipment selection, a load calculation.

    Considering the deadline for qualification for the tax credit: Today, right now, get online and buy HVAC-calc and spend the rest of the day working it. It will be an inexpensive way to determine whether someone is blowing smoke.

  11. #11
    Thanks for all the help! Based on your input we have another HVAC company coming this week for a quote. They said that they WILL be doing a j calc. We're telling the other companies that we wont consider their quotes until they come back and do a j calc.

    A few people have suggested that we try to sell the old furnace on craigslist. Anybody here have an opinion on that idea?

    Thanks again!

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,770
    Let the HVAC company scrap it.
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  13. #13
    I got a general idea of how to size my new furnace based on my old one, how long it is on during the coldest days of the year, and its efficiency. FWIW, I live in Colorado in what is probably a similar climate as yours, though drier, windier and sunnier on average.

    You have a 120,000 input with let's say 60% efficiency (as a previous poster suggested). That means your furnace has an output of 72,000 btus. That should help you start to get an idea of what size you need for your new furnace.

    Does your old furnace stay on all the time during the coldest days? If so, then you probably should try to get about the same output or more from your new furnace. Can you leave your old furnace off for much of the day? Then you probably can go down in btus. Another question is, does it short-cycle: In other words, does it come on for a while, turn off, and then come on again 5 or 10 minutes later? That could mean your current output is higher than you need, or maybe a 2-stage would help.

    I had to go through all of this myself. As many posters in this forum will tell you, it's standard practice in the industry to oversize furnaces. I personally haven't found a single contractor who I feel can reliably "eyeball" what size furnace is appropriate for my house, because it has simply been a part of the culture to oversize them. So you definitely will get a better idea from the manual J.

    I personally am leaning very strongly towards the 80% efficiency. It means I won't have to deal with the extra piping and condensation with the higher efficiency furnaces, and there's less stuff to break down. Also, my heating bills are so low that I would never get back the cost of installation, despite the government rebates.

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