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  • My shop wall air heater

    As I mentioned in the BTU thread, I have a wall air heater I built a couple of years ago. The idea was on the net several years ago. I made adaptations to fit my need.

    Basically the south wall is glass and behind the glass is a cavity or box in which fiber furnace filter media is hung. The fiber is painted flat black on both sides. The filter is hung diagonally top to bottom in the box such that when it is warmed by the sun the cool air on the shaded side moves through the filter to the sun side while at the same time the air is warming and moving upward. The air enters the box at the bottom through a slot from the room and the air leaves the box through a slot into the room at the top. The air movement is entirely by convection and no fans or thermostat controls are used. Below is a sketch of the cross section of the unit.Swall.jpg

    Bulk rolls of filter media can be found at 24" and 32" wide by 20 ' lengths. I recall getting some on eBay for less than $20 per roll. That was a while back. I see some for $40 now. My glass was old storm window inserts that were being thrown away.

    Keep the box and vent slots about 6 inches deep to maintain a chimney effect. To deep a box or too large vents will reduce the velocity of the air through the box. You want it to get into the room and velocity is the means to get it there.

    Below is a picture from the outside of my shop.swall5.JPG


    This is a close up through the glass from the outside. Ignore the reflection of the junk in the glass. Provide the ability to remove the glass for cleaning. This is a wood shop and sawdust gets everywhere. I remove the glass each fall and clean. While the glass is off I remove the filter and blow the dust out of it. swall4.JPG


    This is a view of the floor vent slot from the inside. I've used a piece of filter to catch some of the sawdust before the air gets into the box.swall2.JPG


    This is a view of the top vent slot before I added a plastic curtain to close it at night.swall3.JPG

    Make sure that the room is well insulated. You can gain heat but is does little good if there is a lot lost through the walls and the ceiling. I had a concrete floor. I covered it with 1" foam sheet and 3/4 particle board. You need a wood frame to keep the particle board flat.

    I've had this about 4 years. It works very well. Today is a very sunny 18 degrees F and I can work in a t-shirt.
    Last edited by brododge; 01-23-2013, 12:36 PM. Reason: editorial

  • #2
    Very nice. I love seeing creativity of all sorts, ecspecialy when it is energy saving.

    Keep creating,
    Green

    Comment


    • #3
      o no now i have to build build one ..... simple yet im shure it works well......dont thell my wife.....

      Comment


      • #4
        I am impressed with this
        extraordinarily simple yet effective.
        I wonder however whether an expanded aluminum (like a grease filter) painted black would work better.
        NABCEP certified Technical Sales Professional

        [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

        [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

        [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

        Comment


        • #5
          Great DIY project - your payback period should be a few days in the winter!
          [SIGPIC][/SIGPIC]

          Comment


          • #6
            Originally posted by Naptown View Post
            I am impressed with this
            extraordinarily simple yet effective.
            I wonder however whether an expanded aluminum (like a grease filter) painted black would work better.
            Heat transfer between air and a solid media is very much dependent on surface contact area. Likewise, the collection of energy from the sun is highly dependent on surface area. The small fibers in the filter mat provide a very large total surface area. Also the fibers are such small diameter that heat transfer within the fiber is almost not important. Everything happens on the surface of a fiber.

            Aluminum may transfer or conduct heat energy more quickly than most materials through itself in response to an energy differential. But, the transfer of that energy from the aluminum to the air is highly dependent on the configuration of the aluminum object used for heat transfer.

            I would guess that an aluminum fiber mat might surpass the filter mat(I'm not sure what the fibers are made of) at transferring energy to air if the fibers of the two mats were the same size, color and weave.

            It looks like right now you can go to the local big box lumber place and get a roll of filter mat for about one dollar per square foot. If one shopped the Internet I suspect that price might be reduced. I don't believe that you would be able to find a comparable woven aluminum mat for anywhere near that low a price.

            Comment


            • #7
              Originally posted by Naptown View Post
              I am impressed with this
              extraordinarily simple yet effective.
              I wonder however whether an expanded aluminum (like a grease filter) painted black would work better.
              Painting it black without restricting the airflow could be a trick. Plus, as brododge explained, why even do it.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

              Comment


              • #8
                Originally posted by brododge View Post
                Heat transfer between air and a solid media is very much dependent on surface contact area. Likewise, the collection of energy from the sun is highly dependent on surface area. The small fibers in the filter mat provide a very large total surface area. Also the fibers are such small diameter that heat transfer within the fiber is almost not important. Everything happens on the surface of a fiber.

                Aluminum may transfer or conduct heat energy more quickly than most materials through itself in response to an energy differential. But, the transfer of that energy from the aluminum to the air is highly dependent on the configuration of the aluminum object used for heat transfer.

                I would guess that an aluminum fiber mat might surpass the filter mat(I'm not sure what the fibers are made of) at transferring energy to air if the fibers of the two mats were the same size, color and weave.

                It looks like right now you can go to the local big box lumber place and get a roll of filter mat for about one dollar per square foot. If one shopped the Internet I suspect that price might be reduced. I don't believe that you would be able to find a comparable woven aluminum mat for anywhere near that low a price.
                You make some good points. I agree that the aluminum would be more costly. How loose is the weave in the filter mat you used meaning how far can the light penetrate into the fabric?
                NABCEP certified Technical Sales Professional

                [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

                Comment


                • #9
                  Originally posted by Naptown View Post
                  You make some good points. I agree that the aluminum would be more costly. How loose is the weave in the filter mat you used meaning how far can the light penetrate into the fabric?

                  You can see the filter media in the picture of the floor intake slots. It is about an inch thick and some light goes through it. The back wall of my box is lined with aluminum foil covered foam insulation (I forgot to add that to the diagram) to reflect stray light to the backside of the filter mat. I spray painted the mat in a flat black on both sides and a majority of the inner fibers got paint. But the voids are large enough that there was no paint globbing (nice word) to mess up air flow.

                  I also forgot to say that each column of windows is a separate box. That allows a rigid frame to provide structure to hold up both the windows and the filter media.

                  Comment


                  • #10
                    reply

                    Originally posted by brododge View Post
                    As I mentioned in the BTU thread, I have a wall air heater I built a couple of years ago. The idea was on the net several years ago. I made adaptations to fit my need.

                    Basically the south wall is glass and behind the glass is a cavity or box in which fiber furnace filter media is hung. The fiber is painted flat black on both sides. The filter is hung diagonally top to bottom in the box such that when it is warmed by the sun the cool air on the shaded side moves through the filter to the sun side while at the same time the air is warming and moving upward. The air enters the box at the bottom through a slot from the room and the air leaves the box through a slot into the room at the top. The air movement is entirely by convection and no fans or thermostat controls are used. Below is a sketch of the cross section of the unit.[ATTACH=CONFIG]2569[/ATTACH]

                    Bulk rolls of filter media can be found at 24" and 32" wide by 20 ' lengths. I recall getting some on eBay for less than $20 per roll. That was a while back. I see some for $40 now. My glass was old storm window inserts that were being thrown away.

                    Keep the box and vent slots about 6 inches deep to maintain a chimney effect. To deep a box or too large vents will reduce the velocity of the air through the box. You want it to get into the room and velocity is the means to get it there.

                    Below is a picture from the outside of my shop.[ATTACH=CONFIG]2572[/ATTACH]


                    This is a close up through the glass from the outside. Ignore the reflection of the junk in the glass. Provide the ability to remove the glass for cleaning. This is a wood shop and sawdust gets everywhere. I remove the glass each fall and clean. While the glass is off I remove the filter and blow the dust out of it. [ATTACH=CONFIG]2573[/ATTACH]


                    This is a view of the floor vent slot from the inside. I've used a piece of filter to catch some of the sawdust before the air gets into the box.[ATTACH=CONFIG]2570[/ATTACH]


                    This is a view of the top vent slot before I added a plastic curtain to close it at night.[ATTACH=CONFIG]2571[/ATTACH]

                    Make sure that the room is well insulated. You can gain heat but is does little good if there is a lot lost through the walls and the ceiling. I had a concrete floor. I covered it with 1" foam sheet and 3/4 particle board. You need a wood frame to keep the particle board flat.

                    I've had this about 4 years. It works very well. Today is a very sunny 18 degrees F and I can work in a t-shirt.
                    Very nice. I love seeing creativity of all sorts, ecspecialy when it is energy saving.

                    Keep creating,
                    hyder

                    Comment


                    • #11
                      I wander if you modified anything after this discussion. If so, would you please share how did it turn out?
                      thanks

                      Mod note - welcome and please participate but the next time you post your link I hit the ban button
                      Last edited by russ; 08-07-2013, 04:37 AM. Reason: removed link
                      [URL="http://www.soltech.lt"]saules baterijo[/URL]

                      Comment


                      • #12
                        It works well just as shown. However, I was making too much dust in my shop. So, I installed a new dust collection system. That keeps me healthy as well as keeps the dust from collecting in the filter material of the wall heater.

                        Herb

                        Comment


                        • #13
                          Hi - I love the simplicity of your heater, relying on convection alone to move the heat. I am starting a similar project, and you have given me some things to reconsider. I was of the thinking that the intake and output should be constructed a good distance away from each other, to promote circulation of the air throughout the entire heated space - my scribble has the outflow into maybe 6" flex duct with a 15' run to the back (north end) of the shop, and maybe to the floor? with the intake, like yours, close to the collector, with maybe a small forced air plenum feeding it.
                          Could you comment on the ambient temp at the other end of your room? Do you use fans to circulate the air? With my thoughts of having a flex duct run - I am sure it creates resistance, thus would likely require some forced air at some point.

                          Thanks again - the idea for the filters material is intriguing!

                          hubser5

                          Comment


                          • #14
                            Any time you want to move air horizontally through a pipe you will need a fan. I don't know the size of the area you want to heat but a horizontal fan at the collector exhaust vent would probably be sufficient without the pipe.

                            My shop is 16 feet by 20 feet with a 10 ft ceiling height. The open vents at the top of my collectors provide enough air flow to warm the room. But, the sun has to shine and it takes an hour or so.

                            I am also well insulated and have tight doors. The ceiling is 6 inch fiberglass plus paper based suspended ceiling tile. The walls are 3 inch fiberglass plus covering. The floor is concrete covered with 1 inch foam and topped with 3/4 inch particle board. This room is inside a barn with one outside wall to the east and one outside wall to the south. The other two walls are within the unheated and uninsulated barn. Once my shop is warm it stays that way.

                            For overnight and sunless days I have two 1,000 watt oil filled electric heaters to keep things from freezing. They usually operate sparingly.

                            If I were to make some estimation of collector size to room size (assuming it would be transferable to other construction) I have about 75 sq ft of collector attached to 3,200 cubic feet of room volume.

                            Comment


                            • #15
                              Originally posted by brododge View Post
                              Any time you want to move air horizontally through a pipe you will need a fan. I don't know the size of the area you want to heat but a horizontal fan at the collector exhaust vent would probably be sufficient without the pipe.

                              My shop is 16 feet by 20 feet with a 10 ft ceiling height. The open vents at the top of my collectors provide enough air flow to warm the room. But, the sun has to shine and it takes an hour or so.

                              I am also well insulated and have tight doors. The ceiling is 6 inch fiberglass plus paper based suspended ceiling tile. The walls are 3 inch fiberglass plus covering. The floor is concrete covered with 1 inch foam and topped with 3/4 inch particle board. This room is inside a barn with one outside wall to the east and one outside wall to the south. The other two walls are within the unheated and uninsulated barn. Once my shop is warm it stays that way.

                              For overnight and sunless days I have two 1,000 watt oil filled electric heaters to keep things from freezing. They usually operate sparingly.

                              If I were to make some estimation of collector size to room size (assuming it would be transferable to other construction) I have about 75 sq ft of collector attached to 3,200 cubic feet of room volume.
                              My shop is exactly the same dimensions, with 3 exposed sides. But that is where the similarities end... It is an old slat-board building - I can spit between the vertical cracks from 10 paces, and I am not an accomplished spitter - but I am in the process of removing the old siding, putting in 16 center studs and T-111 siding... even then it will not be tight by any means (eaves, ceiling). I may insulate and OSB the inside. there is no ceiling, only rafters and a tin roof (I could put one in, but the rafters are lowish, and I am tallish). I do have the space to build twin heaters, which I have considered. I have plenty of storm window salvage - like you.

                              I guess getting it insulated is the key - I have a lot of work to do...

                              Thanks again, and congrats on your success with your heater!

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