If PV wire size is #8AWG exceeds the inverter MPPT allowable wire size of 10AWG solark15K inverter?

[viji]

If the PV wire size exceeds the inverter MPPT allowable wire size of 10AWG in a Solark 15K inverter? What do we do?

During parallel connection, the string current will increase, necessitating adherence to NEC derating ampacity standards, which mandate that the wire size should not be less than the minimum required ampacity. To ensure compliance and prevent issues, it becomes imperative to increase the wire size?

 

[electrofelon]

If the PV wire size exceeds the inverter MPPT allowable wire size of 10AWG in a Solark 15K inverter? What do we do?

During parallel connection, the string current will increase, necessitating adherence to NEC derating ampacity standards, which mandate that the wire size should not be less than the minimum required ampacity. To ensure compliance and prevent issues, it becomes imperative to increase the wire size?

how many strings are you paralleling? Can you show us the math on how you came up with #8?

 

[jaggedben]

If 8awg is truly required because of a roof temperature adder or multiple circuits in conduit then you could splice to 10awg at a spot where those requirements no longer apply. Such as in a box or gutter below the Sol-Ark.

 

[Carultch]

If 8awg is truly required because of a roof temperature adder or multiple circuits in conduit then you could splice to 10awg at a spot where those requirements no longer apply. Such as in a box or gutter below the Sol-Ark.

Exactly. Consider what factors are driving the #8 Cu wire, and determine whether they are local to the termination, or whether they are due to the methods (e.g. bundling) and distance (e.g. voltage drop) of routing the wires.

Consider also, the restrictions on each terminal, or each bulkhead connectors if applicable. You may have a MPPT input channel capable of accepting 50A, and you may be able to plug in a #8 connector to the bulkheads, but that doesn't necessarily mean you can pre-parallel in the field and take credit for the ampacity of #8. The 50A input channel may be designed for two separate circuits in parallel, at max 30A each, instead of a single combined 50A circuit. The prewired equipment might only use #10 internally, and can't except the full capacity of the input channel on a single connector.

 

[viji]

how many strings are you paralleling? Can you show us the math on how you came up with #8?

I have paralleled the 2 strings of 8 modules for MPPT 1 and paralleled the 2 strings of 7 modules for MPPT 2. Both strings will be routed through the same conduit and accounted for in the roof temperature adder (0.91) and the multiple circuits derate value (0.8) during calculation.

The calculated Isc (27.02A * 1.25 * 1.25 = 42.2A) dictates that the required cable size is #8AWG to accommodate a minimum ampacity of 42.2A. Given that the ampacity of a 10AWG wire is 40A (40 * 0.91 * 0.8 = 29.12A derated ampacity), we need to opt for the next wire size, which is #8AWG.

 

[Carultch]

I have paralleled the 2 strings of 8 modules for MPPT 1 and paralleled the 2 strings of 7 modules for MPPT 2. Both strings will be routed through the same conduit and accounted for in the roof temperature adder (0.91) and the multiple circuits derate value (0.8) during calculation.

The calculated Isc (27.02A * 1.25 * 1.25 = 42.2A) dictates that the required cable size is #8AWG to accommodate a minimum ampacity of 42.2A. Given that the ampacity of a 10AWG wire is 40A (40 * 0.91 * 0.8 = 29.12A derated ampacity), we need to opt for the next wire size, which is #8AWG.

Consider *where* you are doing this paralleling. Is it paralleling in the array field, or is it paralleled inside the inverter?

If you are paralleling at the inverter, then you don't need to account for double the current, until you do your paralleling.

Sol-Ark's datasheet specifies 44A per MPPT, 3 MPPT's, and 2 strings per MPPT. If #10 wire is the maximum size, you can't connect 44A on a single wire per polarity to each MPPT channel. You'd have to connect 2 qty source circuits individually to the terminals on each MPPT. In your situation, that means running all 8 source circuit wires the full length to the inverter, since you aren't allowed to "decombine" circuits this small. I also recommend using all 3 MPPT channels (MPPT1 = 1 sc of 8, MPPT2 = 1 sc of 8, and MPPT3 = 2 scs of 7), for distribution of power and better ability to adapt to mismatch.

 

[viji]

Consider *where* you are doing this paralleling. Is it paralleling in the array field, or is it paralleled inside the inverter?

If you are paralleling at the inverter, then you don't need to account for double the current, until you do your paralleling.

Sol-Ark's datasheet specifies 44A per MPPT, 3 MPPT's, and 2 strings per MPPT. If #10 wire is the maximum size, you can't connect 44A on a single wire per polarity to each MPPT channel. You'd have to connect 2 qty source circuits individually to the terminals on each MPPT. In your situation, that means running all 8 source circuit wires the full length to the inverter, since you aren't allowed to "decombine" circuits this small. I also recommend using all 3 MPPT channels (MPPT1 = 1 sc of 8, MPPT2 = 1 sc of 8, and MPPT3 = 2 scs of 7), for distribution of power and better ability to adapt to mismatch.

I am paralleling in the array.

Thank you for the detailed explanation!

 

[Elect117]

There is an exception in 310.14(A)(2) that might be applicable.