[stevehull]

Great video! I also second the use of "body pannel suction cup pullers". Saved more than one panel . . . . .

On your solar install, I recommend you put the combiner up on the roof under one of the panels. Then run a single larger cable down to the lock out box. Your code may insist on a breaker for each string, in which case you need to bring each string feed down.

Another option is to put the combiner box (and associated two 20 A breakers) upstairs in the attic. Then run a single larger G cable down to the lock out box. My utility allowed me to have that inside my shop, so long as I gave them a key for the shop. This made for a very "clean" roof look with no conduit coming down the side of the building. It also minimized wire lengths.

Other utilities insist that the solar lock out disconnect be on the outside of the building adjacent to the service entrance area. They may also mandate you put the conduit on the outside. Just do what they ask for . . .

I would encourage you to do a mid feed string and not to feed from the end of the string. A mid feed is about 2-3% more efficient as there is less voltage induced resistance lossses in the trunk cable.

If I recall, you can put sixteen M250's on a 20 A string. A mid string feed would mean eight on one side and eight on the other side. The end string has all 16 in a row and you get substantial current loss compared to a mid string feed. Enphase has done a big write up on this.

In your case, with 24 (?) panels, divide up the total by four. In the case of 24 panels, you would have two strings, each with 12 inverters total, and 6 on each side of two mid string feeds. It actually is not a "feed" but a power source, however, all the voltage "drop" calculations are the same, except it is now voltage "rise". Minimize the voltage rise with mid string feed (aka source).

You will have no problems with the panels. That is the easy part. The rails, brackets, nuts/bolts, grounding, trunk cable lay out takes far more time. Then there is the AC wiring down to a combiner box or whatever. Lots of time - perhaps a couple days by yourself.

Count on one morning (or afternoon) , with two friends, to do the panel install. One person pushes them up and then there are two people on the roof. Three on the roof is too many. You can get a boom truck, but I doubt you will need it.

VERY important. Lastly, buy NEW highly lugged and very soft soled, cheap running shoes. I got some at Wal-Mart for ~$25. I only use them on metal roofs. The new shoes will be "sticky" and the soft and prominant lugs keep you in place on the roof. Do NOT wear boots, shoes or other that have any wear - as you will very soon be off the roof. . . . . Use cheap "sticky" running shoes.

Wash the roof too as only a small amount of dust (hard to even see) makes the metal roof very slippery.

With the M250, it will be best to match this up with at least a 280 W panel. Remember the PTC and the STC are different. If you don't know the diffference, it is important to look it up.

Keep at it!!


Steve

hint: the PTC (real world value) is ~ 90% of the STC value, yet panels are sold by STC (lab conditions). A 280 W panel (STC) would give you ~252 watts maximum PTC. Look for PTC wattage when buying panels. I might go as high as 300-310 W STC panels to maximize your AM and PM solar collection. Yes, you loose a bit by power clipping (at noon), but you get a LOT more kWhrs early and late in the day by slightly "oversizing" the panels.