Outback Power Systems 80 user manual Wire and Disconnect Sizing, Battery Side of the Controller

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 offers little, if any, current boosting or Maximum Power Point Tracking advantage; in effect, 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 specific 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 configured 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. (21.1mm2)

* North America

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