Installing soon and need a double check on my panel placement and wiring

Re: Installing soon and need a double check on my panel placement and wiring

For your panels, they are probably rated at a minimum of 50 lbs per square foot (or metric equivalent) -- That would be ~867 lbs of load per panel!

Those are not insignificant loads--And give you an idea of how strong a structure you will need (i.e., a could of big guys bouncing on the racking for one panel--times how ever many panels you will install).

If your area has morning sun and afternoon thunder storms, then facing towards east may be better. If you get morning fog and afternoon sun, then facing west would be a good idea.

Otherwise, some easterly and some westerly panels will give you the longest number of hours per day to recharge your battery bank--we sometimes call this a "fixed" tracking system. Your batteries will like it. And with today's solar panels lower pricing, fixed trackers may be cheaper/more reliable than building an actual mechanical tracker.

-Bill

Re: Installing soon and need a double check on my panel placement and wiring

Ben,

I think on the house is going to be best--If you lose the roof, adding panel losses will just add to an already otherwise poor day.

So--You might end up with a win/win solution. Reenforce the roof and build a strong rack for the array.

Perhaps look at what they do in Tornado and Hurricane alleys... More or less (the little I understand), don't just use "weight and nails" to tie the roof to the walls and the walls to the foundation (if you have one).

Since you cannot probably get Simpson Strong Ties at your local hardware store--Taking strips of tin (from corrugated roof strips pounded flat. Then well nailed after being wrapped (the best you can) at that rafter support to wall supports and down the wall stud. And the wall stud to foundations.

You don't want the loads" to pull the nails/supports out. The sheet metal should hold the loads and the nails should stop the sheet metal from "sliding" and will help contain the wood from splintering.

Perhaps somebody with more knowledge than I can help here.

-Bill "my guess" B.

Re: Installing soon and need a double check on my panel placement and wiring

I am not sure--Keeping the panels around 3-5 inches from the roof will allow air circulation (hot panels tend to output lower Vmp-array voltages). And if you put them up at 45 degree angle, wind would certainly find it easier to get under them (and provide a "turning moment" or "torque" on the roof--and raising the stresses there).

Plus, leaving the panels relatively close to the roof will keep a "lower profile" for scavengers.

Otherwise, given enough time, energy, and don't give a rip--Solar panels can be stolen. Even big solar farms in the middle of no-where have problems with theft.

You could take a small insulated wire (keep it from being exposed to sunlight/UV if not UV rated wire--insulation may not last for more than a year +/- if exposed) and thread it through the holes in the frame--And connect it to an alarm of some type---When the wire is cut, the alarm is activated (whatever good that is for your place).

I cannot really give you any good answers on framework. Not my field. However, you can sometimes find some good references on the web:

I would go through websites like our host's:

http://www.solar-electric.com/panel-mounts.html

To get some ideas. Iron Ridge used to have some pretty good design documents on their website...

http://www.ironridge.com/products/roofmounting/overview

More or less--You want the mounts you design to not flex/rack/rotate with respect to the panel... I.e., the strength in the system is the racks and structure underneath. The solar panels themselves are very easy to break if they "twist or rack".

Also, Rails that have multiple attachments to the roof (or the ground) are naturally "stiffer" than those mounted on the top of a pole where the wind can cause things to twist around the pipe (think of a long wrench twisting a nut vs a simple framework mounted at the four corners with an "X" cross bracing.

Any, perhaps some folks here can give you some ideas with home made mounts... But you are limited to the supplies you have on had in Africa.

Watch for corrosion between between steel and aluminum... Paint, etc. to keep things from getting wet/corroded between different types of metal will help.

-Bill

Re: Installing soon and need a double check on my panel placement and wiring

It appears from the little bit I have read---I am guessing that the DC side of the system is fairly lightning resistant. You have big lead acid battery which will clamp at ~14.5 volts and also has a lot of capacitance too (large metal plates pretty close together).

Years ago, our host Windsun, answered that from his experience, it was the AC output of the inverters that was most often damaged during lightning events.

So, while I would always recommend care with the DC side of your system to keep lightning away from it (grounding frames to earth ground rod, grounding the battery negative bus to a ground rod, possibly putting surge suppressors between +/- and earth ground)--It is (in my humble opinion) the AC side that is most vulnerable.

So, surge suppressors on the AC side (at main panel for example) would be a good help. And a good short run from AC neutral to earth ground rod (DC and AC earth ground rods should be the same, or at least, multiple ground rods should have relatively large diameter copper wire connecting them all together--in US 6 awg seems to be good minimum size).

One issue with using surge suppressors to earth ground... Many types of noise/signal injection are "common mode"... I.e., both wires go up and down in voltage at the same time. So, a 120 VAC appliances does not see any more than 120 VAC from wire to wire--which is what it is designed for--But can see upwards of 1,800 VAC from both wires to ground--Which is fine too--Appliances are designed for that sort of common mode voltage).

A possible issue with MOVs/surge suppressors/etc... Is frequently they don't "fire" at the same. What happens is that 1,800 volts of common mode voltage is converted to differential voltage (i.e., one of the 1,800 volt wires is "ground referenced" through the MOV to the safety ground). Now, the two power wires have 1,800 volts across them (instead of 12 vdc/120/240 Vac, etc.)...

So--Not always sure which is the better way of doing this--Leave the cables without surge suppression and don't convert common mode to different energy--Or use surge suppressors to dump the energy before it exceeds the Common Mode ratings.

Having actually experience of multiple hits/failures/survivals would be an interesting data set (not in my area of knowledge).

-Bill