A DIY shop heater that costs nothing to run
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  1. #1
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    A DIY shop heater that costs nothing to run

    Not alot of welding in this, but a good and timely project.

    Most of you blokes would be able to knock up one of these heaters in an afternoon. I'll make one before next winter.

    It's a 'solar box heater'. Well, that's one way to search for them on google. There are lots of commercial ones around, but I find it hard to justify the price - around $4,000.

    Without going into too much detail (because there are dozens of versions):

    - Essentially, it's a shallow collector box - maybe 6 foot x 3 foot and one foot deep. This goes on the roof angled to the winter sun. It has solid sides and base (sheet metal would be dandy) and clear perspex face. So the sun hits the face and heats the air in the box.

    - Then you have a 4 inch duct to pull the heated air from the box into the building. In the duct, you have a solar powered in-line fan so the running costs are zero.

    - You need to allow air into the box. You can either just have an entry hole to draw air from outside, or a 4 inch return duct drawing air from the building. The means that the air entering the box will be pre heated.

    www.sunlizard.com.au is one of the Aussie commercial versions.

    www.solair.com.au sell a European sourced product.

    And there are loads of others.

    So there isn't much to these things - that's why I baulk at $4,000+.

    The great thing about them is that the running costs are zero - when the sun shines, the heater pumps warm air into the building. We get lots of winter sun in Sydney and some of you would, too. On days with heavy cloud, it's back to conventional heating.

    PV Solar cells and fans are pretty cheap - I bet less than $100 for a really good one.

    You blokes could knock up one of these things for a few hundred dollars.

    There are lots of little things:

    1. Need to slow the air down in the collector box - baffles - so it stays there long enough to heat.

    2. Painting the inside of the box black dramatically increases the heating - matt black is best.

    3. The ducting needs to be as direct and as short as possible.

    etc etc.

    I reckon some of you should do the research on fan sizes, box size etc and have a go at making and testing one of these things and then I can just shamelessly copy what you've done.

    Scott
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  2. #2
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    Re: A DIY shop heater that costs nothing to run

    I have a friend with one of these solar air heaters on his deer hunting stand. Same basic design and works well.
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  3. #3
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    Re: A DIY shop heater that costs nothing to run

    Did he make it himself?

    What's a deer hunting stand?
    Yeah, I carry.

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  4. #4
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    Re: A DIY shop heater that costs nothing to run

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  5. #5
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    Re: A DIY shop heater that costs nothing to run

    Ah, so a deer hunting stand is sort of like a grown-ups cubby house or tree house.


    I quizzed one of the guys who makes the solar air heaters:

    'So it's over $4,000 for a box, some ducting, and a cheap solar powered in-line fan?'

    'Um. Yep.'


    They work well, though. But if a DIY one worked only 70% as well it's a good free heating solution.
    Yeah, I carry.

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  6. #6
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    Re: A DIY shop heater that costs nothing to run

    Quote Originally Posted by scott brunsdon View Post
    Ah, so a deer hunting stand is sort of like a grown-ups cubby house or tree house.


    I quizzed one of the guys who makes the solar air heaters:

    'So it's over $4,000 for a box, some ducting, and a cheap solar powered in-line fan?'

    'Um. Yep.'


    They work well, though. But if a DIY one worked only 70% as well it's a good free heating solution.
    Some of the more elaborate ones in the past have involved river rocks to hold the heat longer, water circulation, things like that. Four grand seems a little high for the box version.

  7. #7
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    Re: A DIY shop heater that costs nothing to run

    Yeah, rocks etc can be used as a heat sink i.e. they can be heated during the day and release that heat during the night. A brick wall or concrete floor that gets winter sun will do the same thing. Clever architects design houses with thermal masses that get winter sun.
    There are other solutions that use solar heated water to heat a solid masses that then radiate heat.
    So a solar box heater is a retro fit solution. I'm going to install one in my house as part of my current renovation because I like the idea of free heat. But I'm hoping someone here who's much smarter than me has a crack at making one before I have to muddle through it and get it wrong a couple of times.
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  8. #8
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    Re: A DIY shop heater that costs nothing to run

    Quote Originally Posted by scott brunsdon View Post
    Did he make it himself?

    What's a deer hunting stand?
    It's what Texans build so they can sit up high in relative comfort and wait for the deer they have been feeding to come by so they can shoot them. Just yankin' your chain, all you Texas guys so don't get on my case. This is also legal in a lot of other states.

    I will go so far as to say I don't condone it. I just can't see where it has any connection with the defination of "fair chase". My personal opinion is if you can't stay down on the ground and hunt your deer that hasn't been fed and trained to be in a certain place every day you don't deserve to be called a hunter.

    I feed the quail around my place year around. I don't hunt them and neither does anyone else. It would be like hunting chickens. I feel the same about deer that are fed and then hunted from a blind. About like going out and shooting a cow. Some states allow deer hunting with dogs. That's even worse in my opinion. If you can't go out on your own two legs and outsmart a deer you don't deserve to kill one in my book. Just so you will know I used to be an avid deer hunter and headed for the mountains every fall. Time has taken it's toll and I just can't do it anymore.

    OK, my rant is over. I'm sure I've changed no one's opinion of blind hunting. On the same note, no one will change my opinion either.

    This has gotten off the track on the OP. Sorry. Just trying to have a little fun with the blind hunters.
    Last edited by Oldtimer; 08-18-2009 at 11:50 AM.

  9. #9
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    Re: A DIY shop heater that costs nothing to run

    So I guess the indians in the desert here weren't considered hunters either, huh? I love it when opinionated fools spout off about stuff they have absolutely no clue about.
    QamuIs Heg qaq law' lorvIs yInqaq puS



  10. #10
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    Re: A DIY shop heater that costs nothing to run

    Quote Originally Posted by Oldtimer View Post
    It's what Texans build so they can sit up high in relative comfort and wait for the deer they have been feeding to come by so they can shoot them. Just yankin' your chain, all you Texas guys so don't get on my case. This is also legal in a lot of other states.

    I will go so far as to say I don't condone it. I just can't see where it has any connection with the defination of "fair chase". My personal opinion is if you can't stay down on the ground and hunt your deer that hasn't been fed and trained to be in a certain place every day you don't deserve to be called a hunter.

    I feed the quail around my place year around. I don't hunt them and neither does anyone else. It would be like hunting chickens. I feel the same about deer that are fed and then hunted from a blind. About like going out and shooting a cow. Some states allow deer hunting with dogs. That's even worse in my opinion. If you can't go out on your own two legs and outsmart a deer you don't deserve to kill one in my book. Just so you will know I used to be an avid deer hunter and headed for the mountains every fall. Time has taken it's toll and I just can't do it anymore.

    OK, my rant is over. I'm sure I've changed no one's opinion of blind hunting. On the same note, no one will change my opinion either.

    This has gotten off the track on the OP. Sorry. Just trying to have a little fun with the blind hunters.
    That's why I prefer hunting with tripwire strung claymores...much more sporting than blind hunting (unless by blind hunting you mean a blind guy with a rifle)

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  11. #11
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    Re: A DIY shop heater that costs nothing to run

    Quote Originally Posted by DDA52 View Post
    So I guess the indians in the desert here weren't considered hunters either, huh? I love it when opinionated fools spout off about stuff they have absolutely no clue about.
    I would tend to agree with Oldtimer on this one. Having said that, if the indians you mention were hunting for survival, then that's a whole different ball game. When you're survival hunting, you do whatever you can to get food. Modern hunting (even when people eat the game) is for sport, more often than not... and sitting in a blind shooting fed deer just isn't sporting.


    Back to the topic... I've seen a show where they had something very similar to this, only instead of a box that you would let light into, you would have a fairly shallow box with the front face being something like pegboard, only painted black. The board would absorb a lot of heat from the sun, and then the air is sucked in through all the little holes in the hot board/plate. Same effect, but it can be thinner than the 1' mentioned in the OP.

    I think one of these would be really neat, but have to question how effective it would be when covered in snow.
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  12. #12
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    Re: A DIY shop heater that costs nothing to run

    Sure, go ahead and pass judgment on us. But until you are here and know what the hell you are talking about, you will just be yet another loud mouth spouting off. You want to walk around on a plain where the tallest thing is a 2' tall creosote bush for several miles, be my guest. You will not see a single animal, ever. But then what do I know? I only live here and cannot possibly know of whence I speak.
    QamuIs Heg qaq law' lorvIs yInqaq puS



  13. #13
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    Re: A DIY shop heater that costs nothing to run

    Quote Originally Posted by DDA52 View Post
    Sure, go ahead and pass judgment on us. But until you are here and know what the hell you are talking about, you will just be yet another loud mouth spouting off. You want to walk around on a plain where the tallest thing is a 2' tall creosote bush for several miles, be my guest. You will not see a single animal, ever. But then what do I know? I only live here and cannot possibly know of whence I speak.
    well, obviously you left your ghillie suit and your bravo 51 at home

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  14. #14
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    Re: A DIY shop heater that costs nothing to run

    Thanks, DDA52. I would have been real disappointed if someone hadn't taken the bait I threw out. It's kind of like feeding the deer.

  15. #15
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    Re: A DIY shop heater that costs nothing to run

    QamuIs Heg qaq law' lorvIs yInqaq puS



  16. #16
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    Re: A DIY shop heater that costs nothing to run

    :d :d :d :d

  17. #17
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    Re: A DIY shop heater that costs nothing to run

    Well, I hunt dove for sport. I don't eat em. My neighbor gets all mine, my sons and my buddies. But when it comes to deer, I would hunt to eat. I love deer meat. i don't care if it's a sport or not when it's deer. It tastes good and it's cheaper to hunt it than to buy it as far as I can tell. I would just as soon set a trap and catch the antlered beast instead of chasing him around in the snow with my rifle, trying not to spook him. But trapping isn't allowed as far as I know.
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  18. #18

    Re: A DIY shop heater that costs nothing to run

    Things get heated without a heater in this forum! Now, anymore about solar heat?

  19. #19
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    Re: A DIY shop heater that costs nothing to run

    Works great! IN THE SUMMER.


    Just kidding, no cracks about deer hunting either.

    Sounds interesting, may try it this season.
    Tim Beeker.

  20. #20
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    Re: A DIY shop heater that costs nothing to run

    We're heading into summer now, so I'll make one next year.

    I've found a fan. It's 12V but runs on mains power. Costs hardly anything to run. A decent solar panel probably would have cost $300. The fan I've found will have a thermostat i.e. it will only go on when the box heats to a certain temp.

    I'm some renovating this summer, so I'll be putting some ducting in.
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  21. #21
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    Re: A DIY shop heater that costs nothing to run

    It sounds interesting but the thing is how big is the box gonna have to be to provide much heat? A small shop is going to have a bunch of thermal mass to warm up. I don't know how cold it's going to be there in the winter so don't have any idea of how much heat yer gonna be needing to add to the structure. I'd definitely look at the commercial units and see how big they are rated per square meter and that should give you a good idea of where to start size wise.

  22. #22
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    Re: A DIY shop heater that costs nothing to run

    My size will be dictated in part by the fact that I need to haul it up onto the roof of a two storey home.

    A collector box 6' by 3' will produce a fair bit of warm air.

    When the sun shines, it will put warm dry air into the living space.

    I'll use a mains run fan that will draw hardly any current.

    I'm expecting that on particularly cold days or days when there is a lot of cloud, I'll have to supplement the heater with a secondary source (I've got a gas heater).

    Anyway, I'll give it a go and report back - but it won't be till our autumn i.e. April/May.
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  23. #23
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    Re: A DIY shop heater that costs nothing to run

    Few thoughts from someone who's studied buildings as a career. Remember to be sure to provide a good solid air tight way to close off the box. You can easily loose more heat at night than you gain in the day, if the duct leaks. Also you want to insulate under the box as well. Not so much for in the winter, but for the summer. Black roofs are great in the winter but poor in the summer. Thats usually one of the big downfalls of designs engineered to maximize heat gain. They work year round. Frequently they get way too hot in the summer. You save the money in the winter only to spend it in the summer to keep cool. Same old problem thats been around for years with whole house fans. They work great in the summer to remove hot air, but come winter they are almost impossible to insulate well easily.

    Dollar for dollar, you get the most bang for your buck by insulating the house and closing up all the drafts. Once you have done this, other things will gain you more than if you did not insulate. If you insulate really well, just the normal electronics in a home are more than enough to keep it warm in a many climates. The felt yurts of the Asian nomads use this same principal. Even in the harshest winters these tents are quite warm with just body heat. The felt insulation that makes up the tents is the reason. Ever notice that a basement always stays cool year round? Thats due to the insulating value of the ground around it. A cave will almost always be 50-60 deg year round regardless of the season. It's one reason green roofs work so well, and many solar homes are buried in hills and so on.
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  24. #24
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    Re: A DIY shop heater that costs nothing to run

    Hi DSW, yep, it will be a sealed system, but I'll have a vent I can close at night (and the fan will run off a thermostat). In the summer I'll disconnect the ducting (I'm having a hatch put in my roof this Friday so I can get out onto it without needing a ladder.)

    Good point about the insulation under the box. Mine will be raised on one side to catch the sun, so it will be fine.

    My house is double brick and thanks to a recent government stimulus has very good ceiling insulation.
    Yeah, I carry.

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