This is a basic guide to constructing this model solar air heater panel. There are pictures to help guide you.

You will be building a window type unit but this pattern can be converted into a wall mounted or roof mounted unit, with modifications to the duct work and maybe the fan.Our manual will have 4 sections.

I.) Building the solar air panel with its three layers.

II.) Build the window box which includes the plywood frame, the duct work from the panel, the vent holes, fan and wiring and electrical to the 12 volt dc current. Assemble the two boxes together.

III.) Installing and mounting hardware and legs.

IV.) And other considerations.

I. First we will build the air heater panel.

1. Start with the frame for the heater panel. Using 3, 8 foot, 2”x 4” boards, cut the length and width of your unit to fit a piece of 4’x 8’ exterior plywood. (Pre-drill holes in the end of the 2x4 for the 3” screws keeps the 2 x 4 from splitting.) Place the 4 x 8 ft. exterior plywood on top of the frame and with 2” screws put a screw every 6 to 8 inches around the edge of the plywood and frame on the plywood side. (This close spacing helps prevent the boards from warping.)

2. Turn the box over and measure the interior dimensions of the box you just made. (Keep these numbers you will need them again for the heater plate dimensions.) Cut a 1”x 2” strip that will lie along the inside of your frame that the heater plate will rest on. (The actual height will be 1 ½”.) Drill pilot holes for the 1 ½” screws that will hold the ledge pieces snug against the 2 x 4.

3. You have already determined which way you want the unit to run to your window, vertical or horizontal. And where the air vents need to be located.

4. Now you have to lay out your baffle system. You want your baffles to be horizontal in both a vertical or horizontally placed panel. Determine the number of chambers you want to create with the baffles. (The more baffles the more resistance.) Then evenly space and mark where the baffles-walls will go on the plywood. The space that forms the one vertical in-put channel will be the same width as the other space.

5. Cut your baffle-wall pieces, in this case we are using 1”x 2” x 4’ pieces. Drill and counter sink holes down through the top of the 1x (the 1 ½” depth) so they will not split when screwed. (Do not drill into the plywood so the screw will have something to grip.) Use 2” screws to fix the baffles to plywood.

6. Next cut the holes for both the vents. Start a pilot hole then use a gig saw, hole saw, hammer/chisel, or similar tool to cut the circular holes. Screw and caulk the vent connector collar rings into place with the flanges inside on the baffle side of the plywood and the protrusion sticking out side the back.

7. Caulk along around every edge, corner, baffle edge and top of baffle and ledge with silicone caulk. (Not the top of the 2x4 yet.) You do not want any air leaks. Let it set up.

8. While the caulk is setting up, you can go on the next step. With the previous interior measurements, mark the aluminum sheet (heater plate) to fit inside the 2x4 frame so it will rest on the 1x ledge and baffles. With a utility knife, score along the straight edge, on both the length and width. Go over the area several times to cut it deep enough. (You can use a saw or shears but the shears leave a bit of a wrinkled edge.

9. Lay your sheet over an object high enough to be able to move the edge up and down until the sheet breaks on the score line.

10. Lightly sand the surface of the aluminum heater plate to prepare it to be spray painted. Use a cleaner to wipe the oils and sand residue off the sheet before placing it in the frame.

11. The caulk has setup now so carefully lay the heater plate on top of the caulked ledge and baffles. Press firmly along edges and baffles to seal heater plate to the caulked areas.

12. With your black high heat spray paint or the selective coating, lightly but completely cover the aluminum heater plate. You do not want a thick coat of paint. You want the thermal radiation to be absorbed by the plate and thick paint can block this action. Let it dry, then if you want you can use black or clear silicone caulk to seal around the edge of the plate on the top side just for safe measure. (Selective coating is more efficient by absorption but initially more costly. If you use high heat paint it is less absorbent but costs a lot less, and it will take most of 2 cans.)

13. Now you are almost ready to put the glazing on top of your panel. Depending on the strength of your glass you may need to support the Plexiglas from the under side. If you use tempered glass you will not need to support it. But if you want to put one brace in the middle you can do that. We used suspension T-channel (for drop ceilings) as our support for our light weight plexiglass glazing. To do this measure the distance across the width of the panel from the mid way of each 2x4. Take a 1” notch out of the ends of the metal channel strip so the support will rest on the top of the 2x4. You do not want the metal to touch the absorber plate because temperature transfer will occur. Put a dab of caulk under each support and let it set up so it will adhere to the frame. If you want to get fancy you can chisel out a pocket for the brace end on the 2x4.

14. Now it is time to put the glazing on top. Run a generous caulk bead around the top edge on the 2x4 and across the top of the supports. (Use clear caulk on all surfaces.) Let it set up, then place the glass carefully on top of the frame and supports. Gently press and squish the caulk to the edges and let it set up.

15. Silicone seal and nail down a corner round trim around the edge of the frame to cover the edge of the glass and give it a finished look. You can use a metal, wood or plastic trim. The silicone needs to cure for 24 hours.

II. Next the Window Box & Electrical

16. Start with the glazing side down and the plywood side up.

17. Window box. It is important to make a template for the window box on paper or on the unit if you want. If you are going to use a slanted heater panel you will need to consider the variables of the angles. This can be complex and needs a lot of thought before cutting any pieces.

18. Use the measurements of your window or opening: depth, width and height for the box. The height may be more about the fan size and duct work and/or if your window or opening is fixed or vertical. If the space is vertical this will affect your vent hole positioning also. When creating your template for a 45 degree angled panel, the measurement of depth from the panel past the window seal needs to be carefully calculated. Make sure it is long enough from the edge the box not the vent holes to your interior window ledge. Plan for the location and size of the fan and vent holes. Where will the electrical come out and will there be switch controls on the front? Make the angle of the back of the window box conform to the slant of the heater panel. If the unit is flush/flat on the wall the window box will be simpler to plan for at right angles.

19. Now, attach the thermal switch to the absorber plate through the vent hole with 2 short sheet metal screws. Attach a long enough piece of electrical wire to run through a drilled hole/slot in the side of the duct so the wire will run along the outside of the duct work and into the window box. The thermal switch will have crimp on tabs on which to add the wire. (If you use a remote bulb thermostat run the bulb end into the out hole and attach to the rim of the plywood so the end does not touch the metal or the wood.)

20. On the back of the plywood, attach a frame around the vent holes with 1" x 2" strips of wood to hold the window box to the back of panel with screws. If you can give yourself at least two inches on each side of the fan and vent holes when determining box size. You need room for ducting, clamps and possibly insulation.

21. According to your template: measure and cut the sides, top and bottom pieces of the box which includes the 2 inches you need around the duct and fan. The frame is interior and the sides should be flush on all edges. Make sure you calculate for the width of the plywood in your overall dimensions.

22. Screw the plywood to the frame pieces. You may need to drill the screw holes first to keep the wood from splitting.

23. Cut the appropriate holes in the interior face plate on the box for the size fan and duct work that you have chosen to use. Cut the hole to match the fan blade dimension. If you have a collar insert it now with the flange edge on the outside and so the interior piece with connect to the duct work.

24. On the heater panel side, attach the duct work to the two collars. Screw in place, tighten the clamp around the duct and caulk around the edges so the air will stay in the duct. (We used flex duct. You can use dryer vent hose or standard sheet metal duct, which ever works best for your situation.)

25. Next, set the window box over the duct work and wiring and attach the box to the panel by screwing through the plywood and the 1 x 2 frame of the box into the plywood of the heater panel.

26. Brace the middle of the interior side of the box for support.

27. The air flow of the fan. This fan will blow air into the unit forcing the heat through the unit and not over the fan. The thermal switch will be in the other vent hole to read the temperature of the plate and/or air at the out point. Before attaching the fan to the inside of the front panel, you may want to file/cut off the back corners of the fan to make it circular, so the circular tube/duct will clamp around the fan easier. Screw the fan to the back side of the interior door. Next attach the ducting to the fan and the starter collar on the inside of the box. Clamp around this end of the ducting also and caulk to cover air holes.

28. Electrical. Pull wire up from the thermal switch to the top along side the ducting.

The circuit from the wall:

transformer/converter/adapter to the thermal switch to the fan back to the adapter. Cut the end off the transformer that is NOT the wall plug. Separate the wires and strip back as much as you need to reach. It is positive to positive, negative to negative between the adapter and the fan with the thermal switch in between one side. Connect the positive wire of the transformer to any wire of the thermal switch, then take the other wire of the thermal switch and connect it to the positive wire of the fan, then the negative wire of the fan and connect back to the negative wire of the adapter through the thermal switch. The thermal switch or the thermostat polarity does not matter it is just a switch. You can use telecom butt splice which are water proof. If the fan does not turn on the odds are you have to redo the wiring circuit. With the DC fan and adapter you are in much less danger of electrical shock.

29. Cut a groove at the door edge and attach the wire of the adapter/transformer to the box to keep it secure from pulling out. Put the lid on and attach it to the box with hinges or screws.

III. Installing, mounting hardware and legs.

Depending on where you plan to mount your unit and how far off the ground it is, will determine your legs and brackets needed to hold up your unit. Do not rest the wood frame on the ground in case of rain or termites. If you need to, use little buckets with concrete as feet for the legs to set in to keep them more secure and the wood from rotting. If you plan to mount this unit on the roof make sure your warrantee or insurance will cover the holes that you put in the roof. Ask a professional for help.

Placing several units as one continuous unit along a fence line or shed is a good idea for those who do not have a south window. For crawl space heating run PVC from the unit to the crawl space or through a hole in the wall of the building. Make sure it is insulated so you don’t loose the heat along the vulnerable duct work.

Try not drill or screw into the air chambers, if you can help it, so that the hot air does not escape.

Otherconsiderations

When deciding on which materials to use and how much you want to spend, you need to consider several main areas.

• 1. The glazing is one of the most expensive items on the list. Do some research in your area and determine which glazing you can afford or are willing to use. Ideally you want a glazing with 86% transmissivity or better. Look on the internet for solar glazing in your area or that can be shipped to you. We were looking at using sliding glass door glass from a surplus store.
• 2. The coating that goes on the aluminum can also be expensive but it is more efficient. There is one place to get that product and it has to be applied with an air gun. This unit used the black high heat spray paint and it tested at 170 degrees out put on a 70 degree day in the afternoon. It may be enough heat for your use. If you choose to use the selective coating, it absorbs more and creates hotter levels of heat through the plate. I recommend if you the selective coating I would suggest using a sheet metal baffle. (see below) Even thought the caulk we used would hold up to 1200 degrees you want to be careful of very high heat and wood.
• 3. If you want to make your unit more permanent you might consider using sheet metal frame and baffles. The frame would look like an unequal right angle C. The bottom would measure about 3", up at right angle 4" and back over at a right angle about 1". A sheet metal fabricator can give you a price for the 4 x 8 frame. If you use the metal frame you need to insulate it from the unit because direct transference could cool down the unit in cold weather. You can also replace the wood baffles with 1" high C-channel sheet metal baffles.
• 4. Also, there are choices for the thermostat that controls the fan. The options are:
• a.) a thermostat that is used in air conditioning units or attic fans. These tend to have an adjustable temperature range generally between 60 and 120 degrees.
• b.) a remote bulb thermostat gives you more flexibility in length of distance from the area you want to read to the control box on the inside of the house. They are more expensive but may fit your needs better. They also have an adjustable temperature range.
• c.) a thermal switch, which this unit has in it, are easy and inexpensive. They come in only one temperature setting. We used a 110 degree switch. I might go with a 90 degree so it warms up sooner in the morning and stays a little longer in the evening.
• 5. If you plan mount your unit on the roof check with a professional.
• 6. When planning your baffles system remember to lay them horizontal and continuous, if you are going to use more than a single unit. You want your panel to all one piece under the absorber plate.
• 7. And last but not least, if you plan to mount your unit against a wall or as the wall it is recommended to insulate your plywood on the inside with ½" pressed fiberglass board. DO NOT use Styrofoam insulation because it will out-gas cyanide poison into the air when it gets too hot. Very toxic.