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bhebby
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# Posted: 3 Feb 2012 12:25am
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I am thinking about taking an in line fan and 6" duct work and making something to draw hot air and push it down. I only have 8' cielings but I am heating with propane and the hot air stays at the top 4' of the cabin. I have thought about a battery operated fan but they use a lot of batteries. has anyone done anything similar?I have no idea of CFM and how that whole gig works. I need to do some homework on that subject.
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Martian
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# Posted: 3 Feb 2012 07:15am
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Have you thought of taking three 2' sections of 6" single wall stove pipe, putting elbows one each end, and standing or hanging it in front of your heater? The heater will heat the pipe causing the air inside to rise. This will stir the air and require no power.
Tom
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bhebby
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# Posted: 3 Feb 2012 08:05am
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really that will work just fine?I only have 12x20 of space with 8'cielings. Have you done this before martian?have a picture?thanks
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Martian
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# Posted: 3 Feb 2012 08:50am
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Convection always works. Will it move enough air for you? I don't know, but it would cost less than $40 to try it. I'm on the grid, us a wood stove, and have a ceiling fan running 24/7; so its not something I've had to try. But I do feel your (cold) pain. In my last place, I used propane heat and had to put in a ceiling fan so my feet didn't freeze. It doesn't take much circulation to have a dramatic effect on heat/cold layering.
Stand the pipe close to the heater, and it will circulate the air, but if the heater is at one end of the structure and your insulation is minimal, then it may not warm the far reaches. But anything is better than having the air stagnate.
How far from the floor is your heater? Mount it as low as the directions allow.
Tom
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bhebby
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# Posted: 3 Feb 2012 09:19am
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I am mounted as low as I can go about 2 ft or so. I am asking the questions on here so I dont waste money on a project that does not work! I guess my question should be is air flow the key or is it important to have vertical air flow from top to bottom?thanks
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Martian
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# Posted: 3 Feb 2012 10:37am
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Cold air falls; warm air rises. Its hard to 'push' warm air down, but you can lift the air from the floor using convection. The amount of flow up the tube is detemined by how warm you get the tube.
Any method of mixing the air will help even out the temp.
Tom
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bobrok
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# Posted: 3 Feb 2012 07:59pm
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Being off grid I have been trying to come up with a similar solution. I scarfed 2 old 12volt computer cooling fans from some old towers before I recycled them. My plan was to experiment with moving hot air down but Martain's comment about pushing cold air up got me to thinking I will be trying it both ways and see which works better. I was going to get an old cardboard sheet goods or rug tube and rig one fan at each end. I also like the non-fan convection idea, but I dont think i would use a cardboard tube.
That was the plan but I haven't made it up all winter so if I get something done on my first trip up this year I will make a report.
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MtnDon
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# Posted: 3 Feb 2012 08:15pm - Edited by: MtnDon
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I have not built one of these, but they are supposed to work... he sells them but you could copy it
HEATSTICK
The problem with many fans is they make a fair amount of noise. This is supposed to be one of the quieter ones.... and it is very efficient
Zalman ZM-F1 PLUS
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PA_Bound
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# Posted: 4 Feb 2012 10:02am
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@MtnDon- What a deceptively simple and slick solution! Thanks for sharing...
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bobrok
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# Posted: 4 Feb 2012 10:36am
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Wow, nice but $$$$!
If they sell these for $100 there must be some (minimal) function at the very least. Now I am definitely going to the carpet and floring store to pick up a few experimental tubes. Got to try this out in a homemade version. If I cut the tubes strategically, mount the fan(s) and reassemble them this could work!!! :)
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Martian
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# Posted: 4 Feb 2012 12:57pm
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I think you'll find this to be most efficient if you place it as far from the heater as possible. The warmer the air is at the ceiling, the harder it is to suck it down the tube with the fan.
Tom
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bobrok
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# Posted: 4 Feb 2012 01:56pm
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Thanks for the tip, Martian. We do have a colder corner of our interior and I'll try that. Was actually thinking of making two of these contraptions (since I salvaged two fans) and positioning them at opposite ends of the camp. The nice thing about the tubes is that they will be lightweight and portable can I can move them around to experiment. Lot of experimenting to do; 1 tube with 2 fans mounted 1 at the top and 1 at the bottom, or maybe two 1-fan tubes, etc.
Big concern is how much power they will demand and if I can tap off my 12v battery array at the same time I'm using my a/c inverter, or perhaps a dedicated (rechargeable) battery pack for each unit.
Lots to think about and I can't wait to get up there and start this. Gotta get up there when its still heating season or it'll have to wait until fall.
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MtnDon
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# Posted: 4 Feb 2012 03:34pm - Edited by: MtnDon
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A ducted fan like the "heatstick" model will be much more successful at moving air no matter the temperature of the air than a fan that spins in a free air open space, such as a ceiling or table fan. Flat paddle blade ceiling fans are not efficient air movers. The key is the duct. The ducted fan doesn't even have to run all that fast.
I have used the Zalman brand of fans when I used to build custom desktop PC's and servers. They are among the quietest ones.
I think it would be a good idea to make the fan easy to access. Dirt/dust does tend to build up on the blades and over time that can lead to imbalance which leads to vibration and noise.
I have also thought that this idea could be used to move air from the main room where the wood stove is into another room (bedroom?). Possibly teaming up a vertical unit in the warmer main room with an additional piped run horizontal from the outlet through into the bedroom. Should work especially with a second fan in the horizontal run.
The heatstick guy states that the Zalman fan he uses consumes only 0.63 watt at 12 VDC. That's 15 watts in a 24 hour period. Darn good. Like running a 15 watt Thinlite fluorescent light for an hour a day. Most battery systems would barely be bothered by that. Other fans may consume more power.
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bobrok
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# Posted: 4 Feb 2012 03:55pm - Edited by: bobrok
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Yeah, my fans do have a tag on them that gives all of that power info and i think they are eqivalent to this; unfortunately (if you could say that) I'm on an extended vacation from "up north" right now and won't be back home until March. I'm not worried, though. March is still winter up there with plenty of cold left before spring shows up (if you can except this unusually warmer winter we are having this time around)
The other things about mounting the fan towards the bottom would be lower center of gravity perhaps and also a lot less wiring harness to mess with. All things to consider.
Edit: after chasing for that stupid non-electric ceiling fan for the last couple of years I think I am going to permanently hang up that idea. This seems way easier.
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bhebby
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# Posted: 5 Feb 2012 09:14am
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Mtn Don that little fan looks nice. I wonder how I could run that off a 9volt or other battery. I dont have power and it would be on the other side of the room.
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bobrok
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# Posted: 5 Feb 2012 10:41am
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FWIW I tested my 12v fans using a 6v lantern battery and they ran. I don't know if they ran at half speed or not, but they ran. I want to test this more as well, but thought I'd share my finding with you.
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Rob_O
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# Posted: 5 Feb 2012 11:26am
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Quoting: bhebby I wonder how I could run that off a 9volt or other battery
This is all you need.
You will only get 4-5 hours out of a battery so you might consider buying a bag full of rechargables
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AlabamaDan
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# Posted: 7 Feb 2012 04:43pm
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What a great idea! Thanks for sharing. Keep us updated.
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TomChum
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# Posted: 7 Feb 2012 08:03pm - Edited by: TomChum
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A 12v car battery that can't operate a vehicle (for example one with only 10-11volts) might run a little fan for a long time, probably a lot longer than even a handful of "buy" batteries. Usually a battery like that is "free". But not everyone can find such things. As long as you can think of a way to charge it. If you can drill a little hole for the wires you could keep the battery outside.
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bobrok
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# Posted: 7 Feb 2012 09:11pm
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Quoting: TomChum A 12v car battery that can't operate a vehicle (for example one with only 10-11volts) might run a little fan for a long time, probably a lot longer than even a handful of "buy" batteries. Usually a battery like that is "free". But not everyone can find such things. As long as you can think of a way to charge it. If you can drill a little hole for the wires you could keep the battery outside.
Does the lower DC voltage affect fan operation/speed?
Does it matter for this application?
Nice idea!
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MtnDon
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# Posted: 7 Feb 2012 09:12pm
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Lower voltage = lower fan speed. Does it matter, maybe? But it also makes the fan produce less noise.
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kdrtk
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# Posted: 7 Feb 2012 09:13pm
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I move air from ceiling to under the floor. Two computer fans, thin walled 4 inch pvc. Connected to an attic thermostat. Have mine set to go on at 100 degrees and it shuts off when temp has gone down 15 degrees. All automatically, powered by my small 12 volt solar system.
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Anonymous
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# Posted: 8 Feb 2012 09:28am
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I cant tell from the photo but do you have a vent at the bottom? I was going to use duct work but PVC is probably cheaper and easier to work with. What fan did you use?thanks
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kdrtk
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# Posted: 8 Feb 2012 01:53pm
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Mine goes under the floor and comes back out in a different spot, you could just have a 90degree at the floor and a diffuser. The fans are computer fans, 120mm I think, I got high cfm ones for about $10 each. you can get them many places, look at the choices at xoxide.com case fans I think.
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bhebby
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# Posted: 8 Feb 2012 08:34pm
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Cool idea thanks I only have one room so I want to bring it down and out. Not sure if Im going to go with duct work or pvc. I might use that 9volt option until I figure out a power source on the other side of the room.
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MtnDon
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# Posted: 8 Feb 2012 11:07pm - Edited by: MtnDon
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I'm not positive but it would appear that a typical alkaline 9 volt might run for about 10 hours before the voltage dropped to 6 volts. ^ volts is half the fans rated voltage. As such below that point the fan performance would be pretty low I imagine. Not guaranteeing that, just a rough calculation based on an Energizer brand 9 volt performance. It has a 500 or so milliamp capacity at 9 volts.
Look into the cost of a couple of 6 volt lantern batteries. Wired in series you get 12 volts. The rated capacity of an alkaline 6 volt lantern battery is about 11,000 milliamps.
Best would be a rechargable type, maybe NiMH.
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bhebby
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# Posted: 9 Feb 2012 05:24pm
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good call I forget about those batteries saw them all the time as kid,not many things run off those anymore.
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