Help duplicating Will's 48V EG4 off grid system

[lsneon]

After my initial watching of Will's video, I sketched up 28 - 350W panels in 4 circuits of 7. From there, it was my intention to go to a combiner box then route the power into the building via #2 copper. Once inside I would split the load to each EG4 inverter by buss bar. After several re watches, it appears Will forgoes the combiner and routes the PV circuits straight to the inverters. It also appears he has 4 circuits. So now I'm thinking 2 combiner boxes each with 2 circuits of 7. From there pickup with the #2 copper to each inverter or should I ditch the combiner and just route the PV's to each EG4? Distance from combiner to inverter - 20ft. Suggestions?

 

[TomC4306]

How many MPPT's do you have?
If 4, just home run each string THROUGH A CIRCUIT BREAKER to each mppt.
Verify the maximum wire size that can be connected to mppt.
AWG2 is probably not going to fit.

 

[BraydenFromEG4]

If you're using the 6500EX inverter it won't be able to fit 2 AWG wire into the MPPT terminals, but also it shouldn't need wire that large for a solar array since arrays generally have pretty low amperage. Additionally, there can be conflicts if the array's strings are combined and split to multiple MPPTs via a bus.

Unless the array is particularly far, it would probably do fine with 10-8 AWG on each string to the inverter's MPPTs, but 6 AWG is the maximum and it's pretty snug from what I remember. Tom's suggestion is perfect.

 

[EastTexCowboy]

After my initial watching of Will's video, I sketched up 28 - 350W panels in 4 circuits of 7. From there, it was my intention to go to a combiner box then route the power into the building via #2 copper. Once inside I would split the load to each EG4 inverter by buss bar. After several re watches, it appears Will forgoes the combiner and routes the PV circuits straight to the inverters. It also appears he has 4 circuits. So now I'm thinking 2 combiner boxes each with 2 circuits of 7. From there pickup with the #2 copper to each inverter or should I ditch the combiner and just route the PV's to each EG4? Distance from combiner to inverter - 20ft. Suggestions?

Why are you using such a large wire for the PV circuits? Depending on the distance from the panels to your inverter you would likely be fine with 10 AWG. As an example, I have 32 panels, 445w and 455w, in 4S2P configuration and about 100' run with 10 AWG THHN. As pointed out already, the 2 ga wire isn't going to fit anyway.

It's pretty easy to calculate the voltage and amperage on your PV runs then just make sure you're within specs for the inverter and size the wire accordingly.

 

[Adam De Lay]

20' really isn't that far for a string. Each 6500 inverter has 2 MPPTs which can handle 4000W at 500VDC max (including temperature coefficient). I would recommend that you run each string directly to each inverter. Depending on your voltage open circuit of your panels (as well as your max amps) you might be able to parallel two strings together but you would end up having 2 4900W strings where you would have 900W clipped off each string.

To figure out the proper size PV wire, I downloaded the "Voltage Drop" app by Southwire on my phone. You punch in the max voltage, amperage and distance of your run and it will tell you what size cable you can use.

Like the other guys said, you could probably get away with 10 AWG instead of 2 AWG. Would save you a lot of money...

 

[EastTexCowboy]

I agree with the recommendation to run your PV strings through a circuit breaker. I have AIMS DC disconnects outside on all my strings (2 strings per disconnect) then to DC breakers inside (1 string per breaker) then to the inverters. You need some way to do disconnect DC input to your inverters. The breakers will likely suffice but I feel much more comfortable with the DC disconnects. I added the breakers more as a way to let me turn off the PV when I'm working on the system without having to go outside, but they do add an extra layer of protection.

 

[FilterGuy]

To figure out the proper size PV wire, I downloaded the "Voltage Drop" app by Southwire on my phone. You punch in the max voltage, amperage and distance of your run and it will tell you what size cable you can use.

If you follow the NEC requirements, there is an Isc x 1.56 multiplier when determining the current to use for the wire sizing.

The bad news is this means more expensive wire. The good news is that this covers voltage drop for a fairly long run (I use Imp when I am calculating voltage drop).

Fusing & Wire Sizing guidelines for solar panels

To get the paper, click on the orange'' button at the top of the screen. This resource is intended to help the user understand when they need to add Over Current Protection Devices (OCPDs - Fuses or Breakers) to the solar panel array and what...

diysolarforum.com