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Thread: Do I really need 2 furnaces?

  1. #1
    DIY Member nursedoe's Avatar
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    Default Do I really need 2 furnaces?

    I live in the High Desert. We have some pretty cold winters and the heater is used Dec-Mar. My house is a 1950's ranch with 4 bedrooms/ 3 baths. 3/2 are original. In the 1970's they converted the attached garage into a living room and added a bedroom. I have 2 water heaters and 2 forced air heaters and, as you can imagine, very high heating bills!

    I was surprised by some ducting that is in the way of where I want some bookshelves to go. I thought I could just raise the ceiling up, while repairing some damage to my ceiling, when I ran into this huge ducting. It comes from the forced air heater outside my room. There is also a Non-funtional airconditioning unit that is somehow joined in that same vent. The unit sits outside, but on top to the heater, there is a piggy backed section of metal that says air conditioning with hoses and stuff sticking out.

    So, the dilema is this. Do I just cover up the exposed ducting again and give up on the bookcase (it is taller than the ceiling in the area)? Do I pay someone to come and figure out if we can re-route the ducting somehow? Or, would it be possible to somehow join the ducting so that there is just one forced air heater? Would that be cheaper to run?

    The house is about 2400 square feet, with the add on being about 900-1000. I would love to reduce my heating bills if possible. For cooling we have an evaporative cooler on the roof that is vented through out the house and that has separate ducting.

  2. #2
    DIY Member nursedoe's Avatar
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    Default Pictures of Duct

    Here are two photos of the area in my bedroom where the ducting is. I just wanted to raise the ceiling the jutts out into the room. I took out some old cupboards beneath it.


  3. #3
    Computer Programmer Bill Arden's Avatar
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    If I was in the high (and sunny) desert, I would invest in a solar trough heater and just heat the house that way.

    You should also look and see what insulation you have.

    Given the age and the mess, you probably have leaky uninsulated duct's and very little insulation.

    Once you reduce your heating needs, you will only need one furnace.
    Important note Ė I donít know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

  4. #4
    Engineer Furd's Avatar
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    Default

    Nursedoe, good to "see" you back. I've been wondering how you have been coming along with your home.

    I know that you want an easy answer but unfortunately there isn't one. As Bill stated you probably have leaking ductwork and inadequate insulation. I would add to that a poorly designed heating system. The second furnace was obviously added when the garage was turned to living space because the original furnace either did not have sufficient reserve capacity or the ductwork would have been a nightmare, maybe both.

    It's getting a bit late in the season to be doing a complete makeover of your heating system but the place to start is with a complete heat loss calculation.

  5. #5
    DIY Member nursedoe's Avatar
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    Firstly, good to see you too. The bathroom came out great. I did finally hire someone to do the tile as much as I love to do it because I just wanted the job over with. The grout in one corner is flaking out, so I will have to do it myself.

    I will NOT even think about the ducting on my own. I called for estimates. One kid came today and will bring his boss back tomorrow to look at the set up for my side, which is an add on. He said it is common to have two heaters.( I don't think so.) The house is a ranch with about 24 or 25 hundred square feet. He couldn't get up in the attic to look around because the attic door was blocked with some closet stuff I need to move. I called for three or four estimates this week.

    I don't know what the pipe it. It is black. Good eye! I will let you know tomorrow when the kid comes back to give an estimate. I had been hoping to just put one super energy efficient heater for both sides if possible. The kid said he thought even a big heater would be "starving" one side of the house for air flow because it would be too far.

    I don't know about heat loss calculations. But I agree that something has to be done about the efficiency. I don't even know enough to ask intelligent questions.

    Another reason to try for one heater is that I want to gut and remodel two other bathrooms. The main heater is in a hallway and the back of it back up to a shower on the other side. There is obvious water damage and I would love to make the shower bigger. That means getting rid of the heater or at least moving it.

    Solar is an option here. However it is wicked expensive still and I can't afford a big expense ( over 17,000) like that.

    What follows is not related to ducting:

    I don't know much about the duct because I really am afraid of some creature that lives in the attic. It is big enough to make the rafters creak. Big enough to have some sort of wooden ball that it plays with like bowling when I try to sleep. Big enough to pick up mice by their tails and smash them on the rafters back and forth while they scream. Big claws that don't retract and sound like what I imagine badger claws sound like. Big enough that my son who thought Afghanistan was a not scarey won't go up there and see.

  6. #6
    Computer Programmer Bill Arden's Avatar
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    Here in northern MN most places only have one furnace.
    But the minimum code here is R48 in the attic and R12 in the walls.

    I would focus on that creature... it could start the place on fire by nibbling on wires.

    Black steel pipes are normally gas, and that would make moving the duct a lot more expensive.

    Edit: Don't forget the tax credit if you buy insulation.
    Last edited by Bill Arden; 08-19-2008 at 03:59 AM.
    Important note Ė I donít know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

  7. #7
    In the Trades Bob NH's Avatar
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    With two water heaters and two furnaces, it looks like a system that was created for convenience when energy cost was not a big issue.

    Every heating unit has parisitic losses that sends heat up the stack.

    You should consider an energy system audit. There have been a lot of changes in how to move air in smaller ducts. Insulation and some connection of the ducting should include an objective of having only one furnace and one water heater.

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    One thing I would have checked is if the a/c hookup is sufficiently blocked up. Is it an evaporative unit or refrigerated? It is possible you are dumping a lot of heated air out to the sky through the a/c's ductwork to the roof.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default pipe

    What difference does it make as to what kind of pipe it is? It is especially irrelevent to the original question?

  10. #10

    Default Advantages of 2 systems

    Here are some advantages of having 2 systems:

    1. You can have better control in attaining the correct temperature on each of your zones or floors ( I will assume, Furnace 1 is for main floor and basement, and Furnace 2 for 2nd floor).

    2. You will have better CFC's on your 2nd floor. Most houses that are big, 3000sqft have lots of trouble with getting a good flow on 2nd floor.

    Take care..
    Sergio

  11. #11
    Computer Programmer Bill Arden's Avatar
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    Quote Originally Posted by hj View Post
    What difference does it make as to what kind of pipe it is? It is especially irrelevent to the original question?
    The mystery pipe would have to be moved to take advantage of the area after the duct is moved. so moving the duct and not the pipe would be a waste of time.

    Since it was a black steel pipe, it's probably a gas line.
    Important note Ė I donít know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

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