236 V is within the 195 V to 510 V controller MPPT operating range but I've heard that to optimize power transfer the operating voltage for the Schneider 100-600 should be over 250 volts. Anyone know if this is the case? The controller specs and manual don't go into this.
I have not heard this.... but that does not mean much. Having said that, Schnider does a good job of documenting their gear so if it isn't mentioned in the manual it probably is not an issue.
Also - does the sketch below show appropriate breaker protection design for 6,400 W of PV in two strings?
Fusing is not required for one (or two) parallel strings, but
1) The wires (as shown) are considered PV
input circuits in the NEC and they should be sized for 1.56 x ISC = 1.56 x 13.5 = 21.06A
2) If the two strings combine before the charge controller, after they are combined they are considered PV
output circuits. The PV output circuit must be sized for 1.56 x Isc x Number of strings = 1.56 x 13.5 x 2 = 42.12A.
3) You still need a disconnect that breaks both the positive and negative lines. Some people use breakers as the disconnect and that is fine but I would size them for 1.75 X ISC (or greater) to avoid any nuisance pops.
You may be wondering where "1.56" came from.... for more information, please review this resource:
To get the paper, click on the orange'' button at the top of the screen. This resource is intended to help the user understand when they need to add Over Current Protection Devices (OCPDs - Fuses or Breakers) to the solar panel array and what...
diysolarforum.com
The set-up with the DIN rail terminal strips is interesting, but I would discourage it unless you were running some kind of experiment that needed precise measurements of each panel voltage. (The current is going to be the same everywhere in the string so you can measure that anywhere.) The reason I discourage it for any kind of normal installation is that solar arrays are somewhat infamous for having problems in one of the many connections between the panels. Adding in all those DIN rail blocks just makes it worse.
If there really is a need to measure the voltage of each panel, go for it. However, you should just expect that adding all that wiring and all those connections through the terminal blocks is going to be a problem.
BTW: If you decide to go ahead with the terminal blocks here are a few tips to help avoid the problems.
1) Either be sure to use terminal blocks rated for stranded wire or use ferrules on the wires.
2) The terminal blocks are part of the PV input circuit and must be rated for 21.06A or greater. (ISCx1.56)
3) The terminal blocks need to have connections rated for the size wire you are using. (10AWG)
4) Be sure to use terminal blocks that are rated for something greater than the array Voc. (325VDC)
5) Wire it up and torque each terminal screw to spec. Then wait at least 3 days (preferably with a reasonable temp variation from night to day) and then torque them all to spec again. DIN rail terminal blocks have a reputation for the connection 'relaxing' in the first several days. Some folks blame in on heat expansion/contraction and others blame it on the wires settling in. No matter what the reason, you don't want to take a chance when running that much current through the tiny little DIN terminal blocks