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minnm

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Posts: 2
Reply with quote  #1 
Hi all,
I've been lurking for quite a while and have an idea of what I want to build but am confused about certain things.

I am in southern New Mexico and my "house" is an odd assemblage of an old adobe general store and a wood frame filling station. We have high winds here so that's been an important consideration. 


I'm planning on situating the collector facing almost perfectly south in a gully formed by the connection of the 2 original buildings. The advantages for situating it that way are that it will be partially protected from wind by an equal height adobe parapet 2 feet north, I can make use of an existing centrally located 8” duct penetrating the roof left behind by a gas heater that is no longer there, it can be tied into a large wood support beam and it will have unobstructed sun.

The frame will be vertical and made from 2x6 studs with 1/2” plywood backing. The roof mount will be 14 gauge 2.25” x 1.5" galvanized slotted angle jacks
 
spaced every 30” and mounted to the corrugated roof with S-5 corrubrackets
(https://www.s-5.com/products/clamps-brackets/corrubracket/)
 
but unfortunately the jacks will have to be in front of the collector as this location is on the northern side of the roof. The southern side has dodgy framing and the neighbor’s house blocks the sun.

I’m planning on using 3 layers of black epoxy coated aluminum screen
 
and lexan thermoclear glazing 
(https://www.homedepot.com/p/LEXAN-48-in-x-96-in-x-0-236-in-Thermoclear-Multiwall-Polycarbonate-Sheet-1MW4896A/306556472)
 
cut into 4’x4” squares and installed vertically for drainage.
 
 
The wood frame half of my house is currently unheated and freezes in the winter becoming unusable. I’m hoping I can solve that with a collector and maybe also get some heat for the adobe side.
 
Now here are a couple questions to start with (I will have more!):
Should I stick with the 8” duct? Is that a good diameter?
 
Is this a good fan for my application (it will be pulling air)
(https://www.zenhydro.com/ipower-8-inch-inline-fan-770-cfm.html)
or does anyone have recommendations?
 
Any other advice? Or do you see red flags in my design idea?
Thanks in advance!

stmbtwle

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Posts: 2,994
Reply with quote  #2 
Start by insulating cold part of the house.  Solar is nice but it won't work miracles.


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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
minnm

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Posts: 2
Reply with quote  #3 
Yes, I’m already doing that, thanks.
gbwillson

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Posts: 2,398
Reply with quote  #4 

Welcome minnm!

Lurk no more… I lived in Portales, NM for a few years and spent time vacationing in the Cloudcroft area. I thought it would be a beautiful place to retire.

If you’ve never built a solar heater, you sure don’t start small. But in truth, building larger only takes more time and money. The experience needed is the same. 

From what I read you have all your bases covered for the most part, at least from a material standpoint.  Attaching or holding down the glazing can be a small design sticking point, but only because there are many ways in which to accomplish this. 

It’s always easier to use existing openings into a home, such as a window or in your case, a vent from an old gas heater. For the size of your heater the 8” ducts are likely the best. Any smaller and you will have trouble getting enough airflow. Any larger, and you need a bigger opening.

A couple of suggestions to consider due to the dust issue. Use an air filter to keep dust out of the system as much as possible. A quality pleated furnace filter should be enough. Just stay away from the $.99 spun fiberglas filters. They not only do a poor job of filtering smaller particles, but the fibers themselves will end up in the system. I would also recommend pushing air if at all possible. I would suggest a slight overpressure to help keep dust out of the system. If you are drawing air, dust will be drawn into the smallest opening.  And as your heater is larger, a second, smaller booster fan may be needed to help balance the pressure in the system to achieve the slight positive pressure. 

Something else to consider during the design phone of the build is access. Since dust is an issue where you live, you may want easy access to the innards of your collector. Access may never be needed. But if it should be, you’ll be ready. 

And lastly, the most interesting, and varied part of any heater design is the absorber. Without an absorber, a collector is simply a black box which isn’t very efficient. You mentioned using 3 layers of screen. There are several different ways to use screen as your absorber. Do you know how you want to configure these 3 screens inside the collector box? 

Greg in MN

 
Bruce

Registered:
Posts: 143
Reply with quote  #5 

welcome to the Forum!  Lots of people will eventually jump in if you give them enough time.  You do have an ambitious project here.  I agree with what Greg has said about pushing the air instead of pulling it and leaving an option open to add a second fan to pull later if you need it. Based on my experience, the pushed air seems to more evenly spread into the collector. 

I am not sure how you plan to frame it, but I would recommend that you upgrade the back to 3/4 plywood.  You have room to imbed that back into the 2x6 frame...it will be easier to seal that way. It will also provide a good surface to mount other parts (screens, baffles, etc.) and be less likely to bow. I used 3 layers of screen on my zero pass...one layer in the front and two layers in the back and it seems to work pretty well that way.  

I think you should start a new thread in the Project Section once you start final design...A lot of "air heater specific" people will read it there.

Good luck and don't hesitate to give us more info or ask advice as you progress.  Inquiring minds want to know.Great minds like to share. ;-)

Bruce

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