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Thread: What furnace should we get?

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  1. #1
    DIY Member Sincraft's Avatar
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    Default What furnace should we get?

    Ok, need some expert (and possibly amateur) advice here!
    We have been 'thinking' of changing out our furnace for a few years now.

    We moved into this place, a townhouse with shared walls on both sides, but out 1400 sq townhouse utilizes about $300-350 in gas bills per month during the coldest months. Our air conditioner using about $150 during the summer months.

    Our windows are older and are going to be replaced.

    We are unsure what to do about the furnace/air however.

    We have had 4 people here, and the rates they are quoting are FAR higher than most others we know that have had work done in their houses. And each company doesn't seem to agree as to what needs done?????????

    Our old furnace vents through a flu that the water heater is connected to. Two of the companies told me that a 'sleeve' will need to be put up all the way to the third floor out the chimney vent because the pipe is too large for the water heater. Sounds right to me but what do I know.

    The other two told me they could put a blower in and I wouldn't have to do that??? sounds right to me also, but what do I know??

    I've had recommendations to go from SUPER effecient, to not even bothering and just using the same exhaust system instead of outside the side of the house, to push it up the way it is done now, through the shared vent with the water heater.

    We plan on being here another 5 years but I know the furnace is on it's last legs.

    Many of the companies want to replace our somewhat new air conditioner also. Their explanations sound like gobbly gook to me, but again - what do I know..??

    Any advice on this would be great. I want the best furnace I can get for the money, and I'll research that...but I need to know what efficiency to get.
    Many have advised us that we will not recoup our additional costs to go with a higher efficiency. The run from the furnace to the outside is a straight shot and I've offered to do most of the work (removing the old and drilling the holes to the outside..one for the lower ones and two for the higher ones)

    Not sure what else I can do to figure out what one to get...and the reasoning behind it.

    Thanks..

  2. #2
    Plumber Cass's Avatar
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    The first question is what part of the country do you live in. What State.

  3. #3
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Sincraft
    Our old furnace vents through a flu that the water heater is connected to. Two of the companies told me that a 'sleeve' will need to be put up all the way to the third floor out the chimney vent because the pipe is too large for the water heater. Sounds right to me but what do I know.

    The other two told me they could put a blower in and I wouldn't have to do that??? sounds right to me also, but what do I know??
    It sounds to me like they are all saying something would need to be done with the water-heater vent if you have a high-efficiency furnace installed, and I would definitely go with the sleeve or "flue liner" rather than a blower. I have one of those, and it is merely a thin, flexible aluminum duct hanging from the top of the old chimney.

    Quote Originally Posted by Sincraft
    I've had recommendations to go from SUPER effecient, to not even bothering and just using the same exhaust system instead of outside the side of the house, to push it up the way it is done now, through the shared vent with the water heater.
    The decision about trying to keep all heat inside the house by installing a high-efficiency furnace can be a difficult one. Personally, I have an older furnace with an aftermarket heat exchanger on the exhaust to catch at least some of the nickels and dimes otherwise floating out into the sky.

    Quote Originally Posted by Sincraft
    Many of the companies want to replace our somewhat new air conditioner also. Their explanations sound like gobbly gook to me, but again - what do I know..??
    If it works fine, I would look for the installer willing to simply adapt it to fit/work with the evaporator in the new furnace.

    Quote Originally Posted by Sincraft
    I want the best furnace I can get for the money, and I'll research that...but I need to know what efficiency to get.
    High-efficiency furnaces blow virtually no heat out into the sky, but they can also be comparatively high-tech, expensive-to-purchase-and-maintain-and-repair nightmares when something goes wrong.

  4. #4
    DIY Member Sincraft's Avatar
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    Cass, I'm in Pennsylvania.
    Lee - so would you recommend the highest effeciency that would keep with using the old flu system keeping the initial costs down? That would eliminate the need for a flu sleeve or for them to punch out to the outside wall so from what I can tell I would save about 1.2k.

    Nobody can tell me what mine is currently. One said it is 50%, several others 70%. The one that told me 50% is this really old guy that is expensive and swears alot lol - but let me tell you, he seems to REALLY know his stuff. He rattled off a million reason why I should go with an 80%er. I pretended to comprehend but being slow witted, I really only understood about 60% of what he was saying.

    S

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    By careful interpretation of the data spec on the old furnace, you can get a good idea of its efficiency. They usually show input BTU and output BTU...just generate the out/in ratio and you'll be close.

    To obtain the maximum efficiency with an a/c unit, it needs to be matched to a corresponding evaporator unit. The refrigerant on yours may not be compatible, and cannot be used. All new a/c systems must be at least a SEER of 12 or above (some are over 18 now).

    You don't necessarily want to replace your a/c or furnace with the same size as is there now...they often oversized them. You need a good heat loss analysis or you may end up with a new system that doesn't create the best comfort or efficiency.

    The most efficient (I assume gas?) furnaces are 2-stage with a variable speed blower that uses a closed combustion system. The comfort levels available from these are exceptional. Efficiency gets into the mid-90% range. Check out the Federal tax credits before you make a decision along with the local gas utility to see if they have any rebates (I got $1100 back from a new boiler install earlier this year from the gas company).

    The maximum comfort and efficiency occurs when the system is sized properly and can run 100% of the time. You lose energy if it is short-cycled by being too large. In the summer, you especially want it to run most of the time to remove the moisture. If it is too big, you end up with a clammy interior environment. Much better to have it dry and maybe not even as cold. The variable speed fan helps immensly in this application since it starts out slow which keeps the air in contact with the evaporator coils longer, drawing more moisture out with each pass. It only ramps up to max if it can't maintain set temps at the lower fan speeds.

    When I switched originally to a more efficient system, my gas and electric bills went down by 1/3-1/2. My condo is 1100 sq ft in NH, my budget gas bill is $63/month with a gas stove, dryer and hot water. My electric bills went down the most with a good (14 SEER vs a7.5 SEER).

    Now, will it pay for itself, especially within 5-years, probably not, but it will probably make the place easier to sell when the time comes.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Sincraft
    Lee - so would you recommend the highest effeciency that would keep with using the old flu system keeping the initial costs down?
    That is probably what I would do, but I am not saying that would be best for you. I try to keep things as simple as possible so I have at least half a shot at maintaining my DIY status when something goes wrong at 3am!

  7. #7

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    My recommendation is to always go as high effeciency as can be afforded, and to even stretch if possible. Fuel costs are not going down. And, it will always be a plus should the property be sold.

  8. #8
    DIY Member Sincraft's Avatar
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    This townhouse is the freaking money pit. Great deal at first BUT it needed, .... everything. Alot of the places where we live are selling with the old stuff in it, but hopefully when we sell people will realize that we have 100% real marble floors in all the bathrooms, granite or something just as nice for the countertops - and all the vanities / cabinets are SUPER nice.

    The best part is, I got HUGE deals on every piece of supply I put into the house that one would think would be expensive. Marble tile 1.50 a sq...and it's some of the nicest tile I've ever seen. Normally $7 but someone backed out of a deal and I was in the right place. Same with the vanities and the tops.

    The problem now is this stupid furnace. Our ductwork is non functioning and blocked partially and we might have to gut a wall or two to resolve the problem. A guy told me this would cost $4k to do this. I can do it for about $100 so , I guess it's all labor. (of course I'll snake cam it first, which I strangely own now)

    Anyway thanks for the tips guys. I appreciate it. I'm going to go with the person I trust the most and create a spreadsheet and run the numbers of the cost/benefit (which I was desperately trying to avoid!) lol. That will be the be all end all for me...the $$$$ in the end.

    Next is, new driveway *sigh*

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