Ok, in a "nutshell" I'm finding that the max AWG 4 wire the inverter will accept in the screw terminals is falling short of the recommended NEC wire size for wires in conduit when amps from the surge is taken into account. So I'm wondering what the solution is.
More details of the system which will not be grid-tied and a standalone system:
Enclosure and Mppt.JPG
This is exactly what I was thinking of attaching directly to the cement wall indoors (I live in PR and home is cinder block with concrete ceiling/roof. I have both items in this image, the MidNite Classic and the MNDC enclosure. Wires exiting at the bottom left go to the battery bank (x2 12V 100Ah to make 24V battery bank), wires exiting bottom right are PV wires and ground, wires exiting on the left side go to the inverter. (There are numerous knockouts that can be used though).
My inverter is a Victron Phoenix 24/1200. I do not plan to use it anywhere near full capacity, however, I have to size the wiring for the maximum surge (as I understand it). The surge is 2400W which would work out at 100A on the DC side (2400/24) but I was advised to factor in an inverter efficiency of 80% for a safety margin = 125A max on the DC side.
In the image above the wire leaving the left side of the MNDC enclosure should immediately enter conduit going to the inverter if it is indoors? This is what I've understood but this immediately would mean the max Ampacity allowed for the 4 AWG wire would be 85A @ 75C (and only 95A @ 90C) which is below the 125A calculated for a surge putting me in non-compliance with Table 310.15(B)(16). Now at the 1200W it's totally fine as I'll have a max 62.5A (and I'm in no way planning to use 1200W continuous) but I'm under the impression still have to size for double this due to surge potential which has me banging my head against the wall. The max wire the inverter can accept in the screw terminals is 4 AWG - why in the world would they design it like this or have I misunderstood something?
The two ampacity tables for conduit and free air. https://www.lapptannehill.com/resour...ampacity-chart
Any suggestions?
Can I somehow have the inverter 4 AWG wires not entering a conduit so that they comply with Table 310.15(B)(17)'s "free air" values? Maybe another enclosure to house the inverter that joins right up alongside the MNDC enclosure like the MidNite Classic 200 is attached in the image?
Or is there some adapter that would fit into the screw terminals but allow me to attach a larger wire size to be in compliance?
Or what if I use an 80A breaker between the inverter and the battery to protect the 4AWG wire (rated 85A @75C in conduit) from the surge?
Any thoughts appreciated!
Thanks
More details of the system which will not be grid-tied and a standalone system:
Enclosure and Mppt.JPG
This is exactly what I was thinking of attaching directly to the cement wall indoors (I live in PR and home is cinder block with concrete ceiling/roof. I have both items in this image, the MidNite Classic and the MNDC enclosure. Wires exiting at the bottom left go to the battery bank (x2 12V 100Ah to make 24V battery bank), wires exiting bottom right are PV wires and ground, wires exiting on the left side go to the inverter. (There are numerous knockouts that can be used though).
My inverter is a Victron Phoenix 24/1200. I do not plan to use it anywhere near full capacity, however, I have to size the wiring for the maximum surge (as I understand it). The surge is 2400W which would work out at 100A on the DC side (2400/24) but I was advised to factor in an inverter efficiency of 80% for a safety margin = 125A max on the DC side.
In the image above the wire leaving the left side of the MNDC enclosure should immediately enter conduit going to the inverter if it is indoors? This is what I've understood but this immediately would mean the max Ampacity allowed for the 4 AWG wire would be 85A @ 75C (and only 95A @ 90C) which is below the 125A calculated for a surge putting me in non-compliance with Table 310.15(B)(16). Now at the 1200W it's totally fine as I'll have a max 62.5A (and I'm in no way planning to use 1200W continuous) but I'm under the impression still have to size for double this due to surge potential which has me banging my head against the wall. The max wire the inverter can accept in the screw terminals is 4 AWG - why in the world would they design it like this or have I misunderstood something?
The two ampacity tables for conduit and free air. https://www.lapptannehill.com/resour...ampacity-chart
Any suggestions?
Can I somehow have the inverter 4 AWG wires not entering a conduit so that they comply with Table 310.15(B)(17)'s "free air" values? Maybe another enclosure to house the inverter that joins right up alongside the MNDC enclosure like the MidNite Classic 200 is attached in the image?
Or is there some adapter that would fit into the screw terminals but allow me to attach a larger wire size to be in compliance?
Or what if I use an 80A breaker between the inverter and the battery to protect the 4AWG wire (rated 85A @75C in conduit) from the surge?
Any thoughts appreciated!
Thanks
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