Tuesday, December 15, 2009

DIY Solar Part 6: Planning the System Install

Ok, we've got solar panels, we've got tools, now we're ready to start putting them up! Woohoo! Well hold on there partner, the better we plan this out the smoother the install will be. So let's take a minute and a piece of paper to figure out how we're going to do this.

Simple Roof Diagram
Most building departments will require a sketch of where your panels are going anyway, so this is not a wasted effort. If you can do a scale drawing your install will go that much faster. Make a basic sketch of the roof area in question. Then do some reconnaissance and figure out where the rafters are and their spacing. The roof mounts, which will hold the rails, will attach to rafters. Mark the rafter locations on your drawing.

Panel Strings
Solar power systems are laid out in strings to achieve certain voltages and amperages required by the inverter. So if you have 10 panels, you may have two strings of five panels. The panels will be wired in series (positive to negative) generally in that string, to get the voltage up to a level acceptable to the inverter. Refer to your inverter specifications or your kit drawings to make sure you get this right, its critical. You'll want one string in a row, with the next row/string adjacent to it since that one will likely be wired in parallel (positive to positive). Layout the strings and rows on your drawing and make sure its all going to work. Your local building code will probably tell you what the spacing on supports should be.

In this picture, each row is its own string. So the panels in that row are wired together in series.
Then each row is wired together in parallel. This is how most systems are wired, yours may be

Equipment Check
Ok you have a drawing of the system, now check with your equipment again to make sure you've got everything. Nothing like getting everything on the roof only to find out you're missing some mounts. Also, if you're getting permits, its worth a call to the building department to see what stages they want to inspect the system at. Some just want to see the final install, other want to see the roof penetrations, which means you will have to call them before you actually put the panels up.

Roof Specifications
One final note before we get to the actual install. Certain roof materials have requirements for sealing up penetrations and temperature during roof work. If its too cold your roof materials may crack or chip. If you can take a sample of your roof material to a local supply house and have them tell you about minimum temperature requirements and sealants. This ensure that you are not damaging your roof and shortening its life.

Next up, mounting panels. Kriss Bergethon lives off the grid with his wife in Colorado for more information visit his website at Solar Panel Kits.

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