79
PB
30. WIRE AND DISCONNECT SIZING
The FLEXmax 80 is a buck type converter with the following properties:
• 80 amp DC output current limit (default setting)
• Listed to operate continuously at 80 amps (40°C/104° F)
With an 80 amp FLEXmax 80 output current limit and PV array output higher than 80 amps oers little,
if any, current boosting or Maximum Power Point Tracking advantage; in eect, any excess power
beyond 80 amps is lost.
For NEC* compliance and the FLEXmax 80’s 80 amp output rating / MPPT capabilities, the largest PV
array input must not exceed a rated short-circuit current of 64 amps.
Battery Side of the Controller
• All OutBack Power circuit breakers (OBB-XX) are 100% continuous-rated type breakers
• The conductors connected to the breakers must have a 125% safety factor applied (i.e., an 80 amp
breaker must have a 100-amp conductor connected when used at its full 80-amp rating)
PV Side of the Controller
• UL* requires a 125% safety multiplier (before NEC calculations)
• NEC* requires a 125% safety multiplier (after UL calculations).
• The 156% safety multiplier is specic in the NEC* to PV applications only – this “dual” 125% multiplier
is used because a PV array can produce above its rated output in some conditions.
NEC Compliance
• When the 156% safety multiplier is applied, the resulting conductor amperage required is still 100-
amps (1.56 X 64A) and an 80 amp breaker may be used (100% continuous duty rated breaker).
• When a PV array is congured for a higher nominal input voltage (such as 72V PV array), the PV input
conductor can be sized smaller depending on the step-down ratio and the maximum short circuit
current available.
NOTE:
The input breaker must also be sized smaller; it cannot be the normal 80 amp with conductor
smaller than #4 AWG. (21.1mm
2
)
* North America
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