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Thread: Moving warm air to cold area

  1. #1
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    Default Moving warm air to cold area

    Hello - I am not an A/C expert and wish some advice on moving warm air that collects in the ceiling to a room that is not hard-wired into the heating system.

    I have a 14 foot ceiling room that is heated well in the winter and a lot of the warmer air (10 degrees warmer than near the chairs according to a thermal imaging) collects up near the ceiling.

    I would like to move it to an adjoining room via flexible tubing and a in-line conduit fan that can be passed through a vent, into the basement for a 2 foot run to the floor vent in the room that needs the air.

    The run would be approximately 20' from ceiling to the floor vent.

    Any advise on using this method of moving air?

    Will a 6 inch in-line conduit fan placed at the vent in the destination room be powerful enough to suck the air from the ceiling in the adjoining room to the room adjacent to it with the floor vent - it will need to suck air through a 6 inch conduit for approximately 20 feet.

    Thank you.

  2. #2
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    Asking a heating question from Georiga in August??


    I don't think it will do what you are wanting it to do. Moving the air alone is going to cool it down significantly.

    I would concentrate your efforts on why the cold area is staying cold. Is there lack of insulation, leaky windows/walls? Why isn't this room heated? What kind of room is this? Is the basement cold and is cold air being forced up this vent?

    A ceiling fan in both rooms may help even things up, however it's really chilly in one room then it's just gonna blow cool air around.

  3. #3
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    Hmm. Ok. Even if the air is being moved through insulated tubing?

    The room in question is an addition that was added to an existing living room without much insulation. However, it doesn't get very much use anyway and tearing down the walls and putting in more insulation is cost prohibitive.

  4. #4
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    Lots of physics involved with this.

    You can search for "moving air feels cooler" and get all kinds of explanations.

    If there's nothing in the walls you can blow in cellulose fairly easily. It's cheaper in the long run to fix the problem then to keep putting band aids on it. Unfortunately this means more insulation or more heat/ac (and more bills).

  5. #5
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    I think we may have to go with the cellulose solution. Sounds the most reasonable, really.

  6. #6
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    What is the square footage of the basement room?
    What is that basement room like in summer -- comfortable, too hot, or too cold?
    If the ceiling air is 10F hotter than the main level, how much colder than the main level is the basement room?

    Is there any reason you can't use a space heater in the basement room (too much heat, no power, not enough heat, ???)
    Last edited by suemarkp; 08-07-2017 at 11:26 PM.
    Mark
    Kent, WA

  7. #7
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    basement room directly beneath the main level is 25 x 10.
    In the summer the basement room is cool and comfortable. In the winter it is very, very cold
    The basement room can be 10 degrees colder than the main room I am trying to heat.
    The main room I am trying to heat up is only 10 x 10 by 10 feet high - not large but directly above the basement with no insulation between the two.

    So am I better off trying to insulate and heat the basement (directly beneath the room I am trying to warm up) or move warmer air into the room I am trying to heat up?
    There is a small baseboard electric heater in the room I am trying to heat up but since it is only used intermittently, I am averse to keeping it on. It does not have a thermostat but rther a simple dial type.

    Unrelated question: do these liquid-filled electric baseboard heaters use the same amount of wattage when on a low setting as on a higher setting?
    Last edited by bulgin; 08-08-2017 at 06:39 AM.

  8. #8
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    I'm confused with the room you're trying to heat. I thought it was the basement, but it sounds like a room above it. If the basement room below the room you want to heat is only 10 degrees colder, insulation is not going to have a large effect. Perimeter walls, windows, and air leaks will have more of an effect. But you also say the basement is very very cold in the winter, so maybe it more than 10F colder?? Passive things (insulation) is better than active (fans). Insulation in the floor of this 10x10 room should be inexpensive and can't hurt since the basement does get cold.

    I'd also look for the big bang-for-the-buck items in the basement to warm it up. Are any walls exposed to the outside air -vs- being underground? Insulate the air exposed walls first. Are there windows in the basement? If so, are the double pane, or leaky casement types? Consider replacing them or covering them with foam board in the winter. Are there any air gaps to the outside (for hose bibs, wires, pipes)? Seal those with foam. Any doors? Make sure the weatherstripping is good and consider replacing them if they have windows or are uninsulated metal doors. Is there any insulation in the basement ceiling? If not, that would make the floor cold in the rooms above.

    The reason I asked about size and air temp is because that determines how much airflow you need to change its temperature. Most duct fans are 6" fans and move about 80 to 100 cubic feet per minute (CFM). A 10x10 room needs about 100 CFM to condition it when the air going through that duct is 20F warmer or cooler than the room temperature. This temperature difference is called deltaT. The higher the deltaT, the less time the fan will need to run. Ideally, the duct fan would be connected to a thermostat in the room so it only runs when the room is cold. With a 10 to 20F deltaT, this fan may run a lot.

    Verify the specs on the duct fan. You'll be fighting convection (pulling hot air down), so you won't get its rated CFM. A 7" or 8" one may be better than 6", but I'd want something that can do a no kidding 100CFM. As Mr T said, moving air can make you feel cold, so you want a diffuser to spread out and slow down the air. I'd put it low on the wall or floor and use a 4x12 or 4x14 diffuser. There are also duct fan/heat combination units. They need much more power, but the much warmer air coming out the duct will actually feel warm instead of cold.

    Baseboard heaters usually have a thermostat in them if it has a rotating knob. The more clockwise you turn it, the higher temp required before it shuts down. You should be able to verify this by turning it on, and then turning it almost fully counter-clockwise and the heater should turn off (but don't go all the way to the off switch setting which is full counter clockwise and it usually clicks). These heaters are usually a single wattage. But they are supposed to cycle on-off with their built in thermostat. So the average power required should correlate to how you set the knob (it will use less overall power on low because it won't run as long). It will pull full power when it kicks on, but it should kick off when warm. If the thermostat is defective, then it will never turn off an the room should get quite hot (usually the bottom end of the thermostat is around 50F -- if the room is colder than this it may not turn off for a while until it warms up). If that's the case, consider replacing it (but verify the voltage if it is hard wired as some are 240V and some are 120V -- you'll burn up a 120V heater if connected to a 240V circuit).
    Last edited by suemarkp; 08-08-2017 at 02:37 PM.
    Mark
    Kent, WA

  9. #9
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    Mark - many thanks for that very thorough and educational reply. Let me now get more specific:

    I live in a country cottage in New York State where temperatures can get down to the teens for a handful of days in the winter, but mostly around the 20 - 40 degrees in winter months.

    I am not the owner of this cottage and rent it.

    The landlord has thrown in a Breckwell P23 pellet stove with a BTU range: 8,200 to 47,000. This stove is located in the main 324 sf room that has approximately 14' ceilings. This room has very large sliding pocket windows on three sides but they are double insulated and also draped over with insulating cloth in the winter and do not appear to leak at all. The Breckwell is controlled with a thermostat.

    Generally this stove does a fair job of heating up this room although regardless of how long I run it, the air is always unconformable from a persons mid-shin down to the floor which is covered with a very large rug that almost reaches to each corner of the 324 sf.

    This room has a 1000 watt liquid core baseboard heater.

    Beneath this large room is a crawl space with a poorly done insulation job - the insulation is hanging down in a good part of it and because of the narrow spaces it is difficult to repair.

    This crawl space is also where the electric water heater resides, draped in insulation.

    The other rooms of this cottage - the bathroom, bedroom and kitchen all measure about the same but with low, 8-10’ ceilings and they each measure about 100 s.f. each or slightly less. They also have 500 watt liquid core baseboard heaters.

    The bedroom for whatever reason stays comfortable with the electric baseboard setting low on winter nights, it just needs about a two hour heat up period and I’m good to go.

    The kitchen and bathroom are the two stubborn rooms that need get heat into them. Rather than turning on a lot of electrical baseboard heaters in these other rooms (combined with the 1000 watt one in the big room, this can get very expensive) I wanted to drain out some of the heat that pools up in the 14’ ceiling areas of the main room and pump it into the other two room – the kitchen and bathroom - both of which have sealed up 4” x 12” vents going into the crawl space.

    It is not a difficult job to gain access to the crawl space and the sealed up vents are easily accessible from there. So I would like to run flexible tubing from the pool of hot air through the vents and then distribute that heat to the vents that open into the kitchen and bathroom.

    One wrinkle: the kitchen is not over the crawl space (although access to it’s floor-level vent is from the crawl space) but over a semi-finished basement that is much, much colder than the area in the crawl space (possibly because the crawl space has an electric water heater running). Landlord admits that here is no insulation between the floor between the kitchen and cold basement. There are many small double-pain windows in the basement and a lot of exposed concrete and stone from the foundation. There is also a 800 watt liquied core base board heater.


    Electricity is expensive here about .20 cents per kilowatt hour so I’d rather take advantage of the hot pool of air that hovers in the big room than start running a lot of baseboard heaters.

    I have thermal imaging of the rooms which speaks volumes to how the air works uploaded herewith. The last photo shows the pool of hot air near the ceiling and the window there as well.

    Thank you for your consideration. I could use suggestions on the exact or as specific as you can get, in duct fans models, etc.

    Moving warm air to cold area-flir1210-jpg
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    Moving warm air to cold area-flir1186-jpg
    Moving warm air to cold area-flir1184-jpg
    Moving warm air to cold area-flir1176-jpg
    Moving warm air to cold area-flir1150-jpg

  10. #10
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    FYI: Landlord has given me free reign for corrections.

    It is understood that any suggestions here by any party is considered opinions by me and not a statement of fact.

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