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klecroy

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Reply with quote  #1 
Which is best going to put on roof of my office,lots of space?

gbwillson

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Reply with quote  #2 
Klecroy-

If you are starting from scratch, I'd look at making a screen or matrix type solar air heater. They are very effective, and are about as cheap and easy to build as you can get. They can be easily modified internally, depending on the size and amount of heat needed. The two basic designs are a two screen, where the air passes through a couple of angled layers of screen. Another configuration is the ZeroPass, or ZP. This is where the air passes between two layers of screen the length of the SAH. The ZP configuration works best in large collectors which need high volumes of air passing through them for maximum efficiency and the most BTU output. With smaller sized collectors, either design works fine. 

Can you describe the space you are planning to heat? How big, how much insulation, etc.?

Greg in MN
klecroy

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Reply with quote  #3 
Office is 14'x10' 4" insulation was, planning on pulling inside air from floor inside so not to have to heat outside air,thinking this will help,
Pleanty of room on roof,how big should i make it,i know of some 4" thin wall round     tubing ,looks like thin stove pipe, he wants $5.00 for 10' thought this would be like the downspout ?
gbwillson

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Reply with quote  #4 
If you already had the downspouts and they needed a good home it might make sense to use the stovepipe. But the stovepipe sounds expensive compared to using screen for your absorber. Stovepipe is also much thicker than aluminum cans or downspouts so it won't transfer heat nearly as well.

The only time outside air is used is in commercial applications to bring fresh air inside a commercial building. For a homeowner, using 60˚F air off the floor for your collector intake makes so much more sense. You are exchanging the coldest air from the floor with the warm or hot air from the collector. 

As far as the size, a 4x16' collector is a common built size. A 4x16' unit keeps the profile low and allows you to use common building material sizes with little or no waste. It will produce plenty of heat, perhaps too much if there are no windows or exterior doors for a room your size. But it's also easy to reduce the amount of BTU's being collected, if needed. A 4x8' collector will provide you with roughly the same amount of heat as a single electric space heater. If that is enough heat to make you comfortable, great! But...

It's almost always better to have too much heat that have too little! Imagine how you would feel if the collector you built didn't give you enough heat. If in doubt, BUILD BIGGER!

Greg in MN
klecroy

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Reply with quote  #5 
Ok i will build 4x 16 screen. going to lay flat on roof,so one inlet at bottom and outlet at top,right?  pull cool air from floor under screen ,then outlet pulls from above screen?
what size pipe? and do i put fan  in inlet pipe at floor and push air in or at   outlet pipe inside? thanks KL

gbwillson

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Reply with quote  #6 
KL-

Assuming your collector will be horizontal, this means one opening at each end. While you could use 6" ducts, 8" would allow almost twice the airflow, which when matched with the properly sized fan, allows for maximum efficiency and lower noise. If you build using the ZP configuration, I'd go with 8" ducts as it collects as much as 2x the BTU's of the standard 2-screen design. 

The standard 2-screen collector can have air either pushed or pulled through the box. Whereas the ZP needs the air to be pushed, as it helps to properly distribute the air between the screen layers. The ZP also uses a very simple manifold at each end of the collector. But This is nothing more than a board that separates the intake and exhaust areas from the screen area. 

Both builds are essentially the same to build, with the difference being either angled screens or flat screens. The ZP has far better performance, but needs a lot more air to run properly. Both are easy to build, and provide lots of essentially free heat!

Greg in MN


klecroy

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Reply with quote  #7 
Thanks i will ck into the zp.
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