I’ve got a very basic question that I’ve been unable to find a clear answer on and hope someone here can help with.
I’m trying to size cables for a 3P1S PV array and am not overly concerned about cabling losses but want to be sure the cable sizes I’m using are safe.
The 3 380W panels I’ll have connected in parallel have an Imppt of 9.5A so 28.5A peak is what will be running through the wires most of the time.
Isc of the panels is 10.01A and once I correct for worst-case temps of 40C, can reach 10.08A.
So Isc for the 3P1S array needs to be rated for at least 30.24A which translates to 47.25A using the 156% rule (125% x 125%).
For any exposed PV wiring I can use the ‘chassis wiring’ ratings so 10AWG will be enough for 47.25A (though I will probably over spec with 8AWG for the short run to my through-roof junction box).
My confusion comes to the home run through the house where I plan 4-wire metal-clad conduit.
I assume that when in conduit, I can no longer use the ‘Chasis Wiring’ ratings,
but does this mean I must use the ‘Power Transmission’ ratings?
47.25A for Power Transmission means I’ll need at least 4AWG which is much larger than many of the ‘Solar Wiring Calculators’ recommend.
For example, Windy Nation indicates that 6AWG can handle up to 55A: http://www.windynation.com/cm/articles_choosing-right-wire-size.pdf
Which does not correspond to either the 6AWG limits for Chasis Wiring of 101A or the 6AWG limits for Power Transmission of 37A (and hence my confusion).
I have seen some reference to certain of these standards being limited to 3 conductors in conduit, so I’d like to understand what minimum AWG I need for 47.25A in 2-wire conduit (plus ground wire) or 4-wire conduit (plus ground wire).
I wanted to use 4-wire conduit to get 2 array’s-worth of wiring into a single conduit (and a single set of holes) but if that means I’ll need 4-4 versus 2 runs of 6-2 or even 8-2, I may just run two seperate 2-wire conduits instead.
So my question boils down to:
-what minimum AWG is needed to accommodate worst-case Isc of 47.25A in 2-wire metal-clad conduit?
-what minimum AWG is needed to accommodate worst-case Isc of 47.25A in 4-wire metal clad conduit?
I’m trying to size cables for a 3P1S PV array and am not overly concerned about cabling losses but want to be sure the cable sizes I’m using are safe.
The 3 380W panels I’ll have connected in parallel have an Imppt of 9.5A so 28.5A peak is what will be running through the wires most of the time.
Isc of the panels is 10.01A and once I correct for worst-case temps of 40C, can reach 10.08A.
So Isc for the 3P1S array needs to be rated for at least 30.24A which translates to 47.25A using the 156% rule (125% x 125%).
For any exposed PV wiring I can use the ‘chassis wiring’ ratings so 10AWG will be enough for 47.25A (though I will probably over spec with 8AWG for the short run to my through-roof junction box).
My confusion comes to the home run through the house where I plan 4-wire metal-clad conduit.
I assume that when in conduit, I can no longer use the ‘Chasis Wiring’ ratings,
but does this mean I must use the ‘Power Transmission’ ratings?
47.25A for Power Transmission means I’ll need at least 4AWG which is much larger than many of the ‘Solar Wiring Calculators’ recommend.
For example, Windy Nation indicates that 6AWG can handle up to 55A: http://www.windynation.com/cm/articles_choosing-right-wire-size.pdf
Which does not correspond to either the 6AWG limits for Chasis Wiring of 101A or the 6AWG limits for Power Transmission of 37A (and hence my confusion).
I have seen some reference to certain of these standards being limited to 3 conductors in conduit, so I’d like to understand what minimum AWG I need for 47.25A in 2-wire conduit (plus ground wire) or 4-wire conduit (plus ground wire).
I wanted to use 4-wire conduit to get 2 array’s-worth of wiring into a single conduit (and a single set of holes) but if that means I’ll need 4-4 versus 2 runs of 6-2 or even 8-2, I may just run two seperate 2-wire conduits instead.
So my question boils down to:
-what minimum AWG is needed to accommodate worst-case Isc of 47.25A in 2-wire metal-clad conduit?
-what minimum AWG is needed to accommodate worst-case Isc of 47.25A in 4-wire metal clad conduit?
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