300w solar panel system

SFVdave wrote:
Since it's square, 2 mounts on each side, 2 mounts on each side a one on front and back or 2on all four sides? They are 39x39".

Depends on how many screws per mount, and how big mounts.

I mounted much bigger panels 65"x39" on 4 big L-brackets each panel. Brackets are 4x4 angles 6" long, 1/4" thick. So each bracket has 4"x6" footprint. In each 4x6" footprint I used on the average 5 tapping screws #10, some going into the rafters and some just in plywood. With plenty of Dicor under the bracket.

L-brackets are attached to panels with machine screws into the rivet nuts in the sides of panels. I didn't use OEM mounting holes in the panels, those require Z-brackets. The plan was to tilt panels to either side, Z-brackets into the bottom of the frame would make it difficult. "Tilted plan" was later abandoned since 500W flat array proved to be enough for me.

You can probably get away with 4 brackets per panel, 3 tapping screws per bracket. Make brackets long, about 6", to space tapping screws further from each other. Machine screws holding brackets to panels - 2 screws per bracket is enough.

Westend, you are right 16.75 for 2 150w and 17.25 for 3 100w. That's .5 amp difference.
Thanks

grizzzman wrote:

westend wrote:
Wind doesn't make any difference unless you plan to install the modules incorrectly.

I believe the difference you might see is that 3 x 100W panels harvest more amperage than 2 x 150W.

Why do you believe (harvest more amperage )?

Thanks

Generally, what I see with ratings is that by increasing cell count on a module, the gain in amperage is not linear. If you have two 150W modules they may be rated at (8.3 amps/module X 2 = 16.6 A, theoretically). The 100W modules may be rated at (5.8 amps/module X 3 = 17.4 A, theoretically).)

westend wrote:
Wind doesn't make any difference unless you plan to install the modules incorrectly.

I believe the difference you might see is that 3 x 100W panels harvest more amperage than 2 x 150W.

Why do you believe (harvest more amperage )?

Thanks

Will go with larger panels. Since it's square, 2 mounts on each side, 2 mounts on each side a one on front and back or 2on all four sides? They are 39x39".

Wind doesn't make any difference unless you plan to install the modules incorrectly.

I believe the difference you might see is that 3 x 100W panels harvest more amperage than 2 x 150W.

I'd always go with the largest panels that will fit the available unshaded space. Every extra connection is a possible failure point.