50 Panel Install

[dmkjr]

Starting a 50 panel install for a friend in South Carolina. Will update as we progress through. Install is facing due south and it was designed to be able to tilt to different angles. We are using an 18k inverter from EG4, running about 350ft. I increased the required wire size to 8awg and each MPPT input will be running 430voc.

Running 1.25" conduit 36" deep to the garage where the hardware will be installed. There are two other structures on this property that we will eventually install another 50 panels to power.

Batteries are DIY 280ah (Seplos kit) x 48v (51.2) x 5 = 14.33kwh/per = 71.68kwh of energy storage.




Edit 1: We did take each array and break it down into a more manageable method of tilting. It will now tilt 8 panels per section.

While we planned on doing 50 panels, we are going to do 52 panels so we can do 26 panels per side and can have 13 in series, paralleled on each.

 

[sunshine_eggo]

I'm guessing those are 8x8? Has there been an engineering analysis for wind loads? Cantilevered 8x8 are not as strong as one would think. You do have a lot of them, which gives me less willies, but does not yield warm fuzzies.

 

[Solarcabin Channel]

Hey, those mounts look familiar!

Are they adjustable?

Added: I see where they are adjustable now.

 

[sunshine_eggo]

Are they adjustable?

it was designed to be able to tilt to different angles.

 

[Solarcabin Channel]

I see where you said they are adjustable now!

Looks solid. Will you have different settings for different seasons?

 

[RV10flyer]

Looks like 6x6’s and will be fine. Looks good.

 

[dmkjr]

I'm guessing those are 8x8? Has there been an engineering analysis for wind loads? Cantilevered 8x8 are not as strong as one would think. You do have a lot of them, which gives me less willies, but does not yield warm fuzzies.

I am an engineer, but I did not do wind load into the calculations. I didn’t even calculate much beyond strength of materials x150%.

They are 6x6 posts, concreted in HD psi.

I do believe I’m going to put a few hurricane straps on the downslope as well, just to keep pressure off the fulcrum.

 

[dmkjr]

I see where you said they are adjustable now!

Looks solid. Will you have different settings for different seasons?

Yes, but only plan on two season changes.

 

[sunshine_eggo]

Yes, but only plan on two season changes.

FWIW, I designed my racks to have Summer, Winter and Fall/Spring tilts. I've never changed it from Fall/Spring, but I am in AZ. My winter POWER production is typically 80% of rated, and my worst month is December with 4.75hr of insolation.

 

[FilterGuy]

Starting a 50 panel install for a friend in South Carolina. Will update as we progress through. Install is facing due south and it was designed to be able to tilt to different angles. We are using an 18k inverter from EG4, running about 350ft. I increased the required wire size to 8awg and each MPPT input will be running 430voc.

Running 1.25" conduit 36" deep to the garage where the hardware will be installed. There are two other structures on this property that we will eventually install another 50 panels to power.

Batteries are DIY 280ah (Seplos kit) x 48v (51.2) x 5 = 14.33kwh/per = 71.68kwh of energy storage.

View attachment 172928


Edit 1: We did take each array and break it down into a more manageable method of tilting. It will now tilt 8 panels per section.

While we planned on doing 50 panels, we are going to do 52 panels so we can do 26 panels per side and can have 13 in series, paralleled on each.

What panels are you using? How are you splitting them amount the 3 MPPTs?

 

[ksmithaz1]

#8 is 40A(nnoying) and somewhat expensive. 13 * VOC = ? I = ? I'd home run each string with #12 into a combiner box back at the garage, then #8 from there back to the MPPT. I'd individually breaker/surge each string. Makes it easier if you need to work on a chunk of it without taking the whole thing down. Unlikely you have > 16A coming off your panels.

 

[pvgirl]

#8 is 40A(nnoying) and somewhat expensive. 13 * VOC = ? I = ? I'd home run each string with #12 into a combiner box back at the garage, then #8 from there back to the MPPT. I'd individually breaker/surge each string. Makes it easier if you need to work on a chunk of it without taking the whole thing down. Unlikely you have > 16A coming off your panels.

Some of the panels with Isc in 13-14a range put ampacity with the NECs 156% rule in to 8 AWG or even 6 AWG territory with 2 strings in parallel.

 

[ksmithaz1]

Some of the panels with Isc in 13-14a range put ampacity with the NECs 156% rule in to 8 AWG or even 6 AWG territory with 2 strings in parallel.

Yep, I'd just do it back at the garage instead of a combiner box outside. Personal preference, if there is a problem I can turn off the offending string without running outside, then fix it when I've got the bandwidth.

 

[dmkjr]

Yep, I'd just do it back at the garage instead of a combiner box outside. Personal preference, if there is a problem I can turn off the offending string without running outside, then fix it when I've got the bandwidth.

I have ran the circuits back to the garage. I have a fused disconnect at the panels and disconnect at the garage as well.

 

[niktak11]

Some of the panels with Isc in 13-14a range put ampacity with the NECs 156% rule in to 8 AWG or even 6 AWG territory with 2 strings in parallel.

Do you get to start from the 90C column for the 156% rule like with other derating factors?

 

[Shimmy]

Yep, I'd just do it back at the garage instead of a combiner box outside. Personal preference, if there is a problem I can turn off the offending string without running outside, then fix it when I've got the bandwidth.

Also makes it significantly easier to modify things if requirements change.

 

[Shimmy]

Do you get to start from the 90C column for the 156% rule like with other derating factors?

My interpretation is you would need to use terminal temperature rating rather than 90C, since the first 125% is to cover Isc running over nameplate in some conditions, and the second 125% is continuous rating.

 

[niktak11]

My interpretation is you would need to use terminal temperature rating rather than 90C, since the first 125% is to cover Isc running over nameplate in some conditions, and the second 125% is continuous rating.

I guess if all else fails you could switch an existing wire run to use 90C terminals

 

[pvgirl]

Do you get to start from the 90C column for the 156% rule like with other derating factors?

It's not really a derating, it's the calculations for current and wire ampacity in the PV section of code. We are still restricted to temperature limits of 110.14(C)(1) that keep us using the 60c column unless we are dealing will connectors and equipment that are rated for higher temperatures, So unless the inverter, disconnect, and all connections in between are rated to greater the 60c you gotta use the 60c column.

 

[glandpuck]

Boy this is scary. Wooden structure that tilts with a life expectancy of 25 years or more? I doubt it. It should have been done with 2" schedule 40 galvanized pipe with 2 rows of vertical posts facing south and the post heights cut to produce the optimum angle. Tilting the panels twice a year will not produce much more power and adds flexibility into the design. Doesn't wood contract and expand? Won't this effect matter when the panels are bolted down? Is this going to have enough ballast and strength to handle 125 mph wind that may come through the area? I hope you spend a lot of time on the fire suppression system with your home made DIY battery kit. If this guy was really your friend you would have installed a metal ground mount and purchased UL9540a batteries for him.