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  1. #1
    Join Date
    Apr 2008
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    Question Moving heated air with inline fans?

    Hello, All:

    In an effort to keep some money in the bank this winter instead of buying heating oil, I have purchased a wood-burning fireplace insert to help heat the house. Here's some background info and my questions.

    The house is a 10 year old contemporary cape in Maine (think long winters). It is insulated well and has double-insulated windows. Overall, it is a pretty efficient home. The main heating system is an oil fired forced hot water system. The fireplace insert is modern, high efficiency and is located on he first floor (of an open floor plan) in a room with a 24 foot cathedral ceiling. It has a blower and is capable of heating 1800 sq feet of house (my house is approximately 1,850 sq ft). The bedrooms I want to get heated air to are on the second floor down a halway, with unheated attic space above.

    My project: I would like to install an inline fan/venting system to draw the warm air from the upper reaches of the cathedral ceiling (off a wall where the bedroom hall goes back, not in the cathederal ceiling itself) back to the bedrooms. There are three bedrooms, with the run ranging from just a few feet to approximately 20 feet. I would terminate in the ceiling of each room with a typical forced hot air vent.

    My plan: Cut up high into the existing wall and add a "return air" type vent opening to draw warm air from the upper cathedral ceiling area. Then I would run insulated ducting to an inline fan/motor in the attic, to which I have easy access. I would build some sort of insulated plenum(?) box and pull three runs of insulated ducting off of these to each of the three bedrooms. I'm guessing 6' duct or whatever the inline fan/blower required.

    My question: Does this make sense to do? Currently I am simply placing a fan at the end of the hallway and blowing the warmer air down to the bedrooms. The current method seems less efficient than using the inline method described above. Would I lose the heat in the air over the runs described, or would the insulated duct presere it? Your thoughts?

    Additional Concerns: (1) Would it be better to run individual returns/fans that are switched in each bedroom instead of one inline fan/blower for all three? Would this provide better balancing of heat distribution? (2) Are there any concerns about taking away combustion air from the insert, causing it to either not stay fired or possibly creating a hazardous situation?

    Any advice or experience you could offer would be greatly appreciated! My main concern is that the heated air not be wasted by just sitting up in the cathedral ceiling area. I currently have two ceiling fans mounted there with them rotating to push the air down, but not down the hallway where it's needed in the bedrooms.

    Hope I gave enough specific information to give you a mental picture of what I want to accomplish!?

    Thanks, Tim

  2. #2

    Default Re: Moving heated air with inline fans?

    It sounds like you need an air handler in the attic which is a central system and--normal. and you can always add central air if needed down the road.You may want to use a fan with a speed control and built in thermostat in seriers with a room thermostat.
    If the supply air to the rooms is to cold it won't run and/or shut off if the room satisfies.That way you can set it and not have to switch it on and off by hand.

  3. #3
    Join Date
    Apr 2008
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    74

    Default Re: Moving heated air with inline fans?

    Yes, I thought about an air handler, but wanted to keep costs low and still have individual room control ability.

    Would the inlines provide enough CFM to accomplish what I'm looking at doing, yet still be economically cheaper to install than a full air handler unit? I've seen varying CFM ratings, but don't want to over-buy for what I'm trying to do.

    I also was looking at a do-it-myself project instead of having to hire someone to come in and pay the labor on that.

    We really don't need air conditioning here in Maine. . . it only gets really hot for a couple of weeks per summer and I can't justify the expense.

    Tim

  4. #4
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    Aug 2007
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    Default Re: Moving heated air with inline fans?

    To be honest I'm thinking the results will be less than you're expecting.

    The fireplace is not a constant source of heat ... meaning the amount of heat will vary as the intensity of the burning varies.

    Also , by increasing air draw upward will take away from the heat being distributed on the lower level ... creating an unbalance. This may also create drafts within the lower spaces which actually could make you feel cooler because of those drafts.

    With the complicated arrangement of blowers and ducting by the time this air is being discharged from the vents in the ceiling may end up being mildly warm but drafty .... again may feel uncomfortable because of those drafts.


    Just a thought.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  5. #5
    Join Date
    Apr 2008
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    Default Re: Moving heated air with inline fans?

    Thanks again for your replies.

    If my master plan won't work as I had expected, do you have any ideas short of reverting back to my existing forced hot water system?

    Thanks, Tim

  6. #6
    Join Date
    Apr 2008
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    Default Re: Moving heated air with inline fans?

    Well, I took the plunge and decided to build my "system" as a test to only one room, instead of three as originally intended. I ran it to the farthest room down the hallway.

    The installation went without a hitch -- other than that I ran short of romex for the drop to the variable speed switch and back up to the fan.

    I ended up getting a 260cfm Fantech inline fan and insulated 6" duct. Once every thing was hooked up, I fired it up and it absolutely moved the heated air to the room. It is amazingly quiet -- I never would have believed it.

    Where before I easily had a 10 - 15 degree difference between the room where the fireplace insert is located and the back bedroom, I now have about a 3 - 5 degree difference.

    It appears I have accomplished what I set out to do, without creating any negative impacts to insert performance or other concerns mentioned in the early responses.

    Thanks for your input. Just wanted to follow-up on my success. We'll see how well it performs when it gets REALLY cold outside. So far only down into the upper 20's, lower 30's. Canuck knows what I'm talking about!

    Tim

  7. #7
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    Default Re: Moving heated air with inline fans?

    So far so good ... good stuff.

    Yep ...... please do post back with updates .... I'm curious how this performs when it does get REALLY cold
    "" an ounce of perception -- a pound of obscure "
    - Rush

  8. #8
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    Aug 2007
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    Default Re: Moving heated air with inline fans?

    Awesome!

    I'm curious as to your total cash out of pocket for the project.

    I'll also say that I like infrared's idea about a stat in conjunction with the speed control for the fan.

    I would think that the higher your intakes are on the high ceiling the higher the temp to the ducting to the rooms and also, the more insulation you can put on the ducts the better.

  9. #9
    Join Date
    Apr 2008
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    Default Re: Moving heated air with inline fans?

    Hi, All.

    Out of pocket was around $250, not including my labor (free). I also have approximately 20 feet worth of insulated duct left if I decide to do an additional room.

    I thought about having a termostat in addition to the variable speed switch, but I'm no electrician and couldn't figure out how to incorporate one into my system. Good idea I think, so that the fan wouldn't be pulling air when it was cooler than desired during the night.

    I put the intake duct as high on the cathedral ceiling wall as I could get to from inside the attic. On the wall the top of the duct/vent cover is about 6 inches down from the ceiling. I took the approach that heat rises and the warmest air would be nearest to the ceiling.

    The insulated duct seems to be pretty good. I'd have to check the R-value to give more detail, but the insulation is about 2 inches of thick pink fiberglass. If necessary, I have easy access to wrap it with more insulation.

    Overall, the difficulty of this on a 1 (easy) to 10 (hard) scale was about a 2. The research and planning kept it from being a 1.

    Conclusions: (1) Research and design prior to buying anything. (2) Buy only good materials -- makes fitting everything together that much easier. (3) Sometimes you just have to say "What the heck" and go with your gut that your idea might not be as crazy as others say. (4) Do it yourself and seek advice for what you don't know (thanks TOH discussion guys!).

    Tim

  10. #10
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    Default Re: Moving heated air with inline fans?

    I thought about having a termostat in addition to the variable speed switch, but I'm no electrician and couldn't figure out how to incorporate one into my system. Good idea I think, so that the fan wouldn't be pulling air when it was cooler than desired during the night.
    If you understand how relays work you could hook one up between the thermostat and the speed switch.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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