Analytic Systems SolarMax SMP100, Installation & Operation Manual

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Every brand of panel is different, so ensure you are familiar with your panels’ specifications. Also be aware that
weather and temperature will affect the Voc of your panels. A higher temperature will produce a lower Voc and lower
Vmp voltage, while lower temperatures will produce a higher Voc and higher Vmp voltage. To determine the corrected
Voc, consult the data sheet for your solar panel and allow for the lowest possible temperature the solar panel will
be exposed to. If the data sheet is not available, use the table below to make the calculation using the formula Voc
Expected = Voc @ 25C * Correction Factor.
Temperature Correction Factor
25° to 10° C (77° to 50° F) 1.06
9° to 0° C (49° to 32° F) 1.10
-1° to -10° C (31° to 14° F) 1.13
-11° to -20° C (13° to -4° F) 1.17
-21° to -40° C (-5° to -40° F) 1.25
Wire Sizing
The distance between the PV array and the controller will be a factor in choosing an optimum string voltage for the
SolarMax. The higher the input voltage the smaller the wire can be for any given amount of power. Be sure to consult
your local electrical code specifications regarding wire sizing.
SolarMax is designed to deliver a maximum of 100 amps to the output. The wire size chosen must be rated for this
much current over the length of the run between SolarMax and the batteries. The NEC requires that the output
conductors have an amperage capacity of 1.25 X the rated current after all temperature and conduit fill corrections are
calculated. For the SolarMax this means conductors must be rated to carry 125 amps. The minimum cable necessary
to carry the full rated output of the SolarMax is #2 AWG, corrections for cable run length, conduit fill and temperature
could result in a larger wire size being necessary, to a maximum of #1/0 AWG.
The maximum input current is a function of the array Short Circuit Current (Isc), assuming a failure of SolarMax that
creates a short circuit on the input. In this case, multiply the Isc rating of one panel times the number of panels in
PARALLEL to determine the maximum short circuit current.
PV input circuits require a double correction factor for over current so PV Isc (short circuit current) must be multiplied
by 1.56. All PV input wires must be sized accordingly. This apparent over sizing is done to reflect the fact that solar
modules can, and often do, produce more than their rated power in conditions of heightened insolation and cold
temperatures. Any PV input disconnect or circuit breaker must also be rated at 1.56 of array Isc.
Coming back to our example solar panel, the Mitsubishi PV-MLE270HD, the Isc for one panel is 9.18 amps, and from
the charts we can see that there is almost no temperature coefficient. Assuming 5 panels in series for 1350 watts per
string, and 7 strings for a maximum power of 9450 watts, the maximum short circuit current would be 9.18 x 7 or 64.26
amps. Multiplying this times the safety factor of 1.56 gives a maximum of 100 amps, so likely in this case, the same
wire could be used for the input wiring as the output wiring assuming similar run lengths.