Did I miss something? How to cut copper wiring costs when distance is a given?

[energyhunter]

Three basic questions:

1) Is 6 AWG stranded copper wiring adequate for (4) 80 ft runs; 3 conductors ea plus gnd; 2 grid/2 load?

2) What is minimum size PVC pipe to run Grid & Load together, (8) wires ea in 2 pipes?

3) Online copper wire source is way less than big box stores, but still ridiculous...is there some wholesale outlet that sells to mom and pop for less?

System in process of purchase from SS:

(2) EG4 6000xp (12K)
(2) EG4-WallMount Battery (28.6K)
(28) Aptos 400w BF sub panel

The circumstances:

Utility Grid is backup only, after solar panels and battery storage (SBU)

Rural county property, 1500 sq ft house w/2 adults has outside 200a main electrical panel - Critical load panel 200a mounted next to main w/most circuits switched over to CL

Solar panels are in 4 strings in series, 7 per string, mounted as roof of carport, adjacent to 16' x 24' shed that houses inverters and batteries

80 ft distance between shed w/inverters and main/cl panels on opposite side of house

Grid & Load copper stranded wiring (6/3 NM-B plus gnd between inverters and CL panel, 80') mostly along joists in crawlspace with 11 ft underground at 24" outside house to shed. Wiring to run inside electrical PVC schedule 40 mostly under house and schedule 80 where entering and exiting the ground. (50 amp breakers)

Thank you, if you got this far, for enduring my whining. Just hoping I missed something!

 

[cs1234]

Delete this.

 

[energyhunter]

Most people are probably running much smaller wire, like 10awg at 13amps per string. You will certainly have very minimal losses if you run 6awg.

Try something like this, to calculate your losses.. see what you find acceptable.

You know, I realize now that my greatest concern has been heat, as I figured 2 or 3% voltage loss was acceptable. The inverter manual recommends 8awg, but says nothing about the distance of the run. Somewhere I read that using 8awg over a 100' run might be warm, about 75f. I'm showing my ignorance, but after all that is why I'm here. Thank you CS1234 for responding. You are giving me hope.

 

[cs1234]

Delete this.

 

[energyhunter]

You wanted to run 4 separate strings right? 7 panels, at about 40voc each.. 280vdc per string.. about 13 amps? That's small potatoes.

Don't worry about the heat on the wire.. it's spread across 80' of wire per run. Just make sure you are staying within the conduit fill limits for your wire gauge and wire temperature rating.

I think you would be fine with 10awg. Even that is only 1% loss at 100'.

Oh, I just noticed you were also talking for your AC runs.. might want a higher gauge for that.. for the loads. But the solar panels don't care.

Well, I think we had a miscommunication, my fault for not mentioning the AC. I already knew that 10 was fine for the PV wire. Can I safely run 8 awg for the AC conductor loads at 80 ft? ...and the conduit fill limit is still out there...I was hoping 8 wires in 1.5 inner diameter PVC...?

 

[zanydroid]

Three basic questions:

1) Is 6 AWG stranded copper wiring adequate for (4) 80 ft runs; 3 conductors ea plus gnd; 2 grid/2 load?

2) What is minimum size PVC pipe to run Grid & Load together, (8) wires ea in 2 pipes?

How do you get 8 wires / 2 pipes? Do you mean L/L/N/G in both pipes?

12kW = 50A? Yes #6 is fine... except you mentioned 6/3 Romex which is kind of confusing because Romex is not rated for conduit installation outdoors. 6/3 romex is not enough if there is a possibility you want to pass 12kW from a grid tie inverter in the future, since those inverters require a 125% continuous factor, 1.25 * 50A = 60A, while 6/3 Romex can only carry 55A.

For #8. #8 THHN is fine for 50A but 8/3 Romex is not fine.

For conduit. Download a conduit fill calculator to your phone and start playing with it (I can open mine up, but it's probably easier for you to do it yourself). My guess without opening it is that 3/4 SCH80 can maybe fit 3x #6 CCC, 1x #10 EGC.

EDIT: OK, opened it up... 3/4 SCH40 can fit but 3/4 SCH80 cannot.

Regarding voltage drop. How long per day are you really going to be at 50A? Your batteries can only feed that for 2.5 hours, so you'll need solar output to be perfectly lined up... and if you have long running 50A loads you're likely to overload the inverter anyway.

3) Online copper wire source is way less than big box stores, but still ridiculous...is there some wholesale outlet that sells to mom and pop for less?

Use aluminum where the cost starts to make sense is all I can say about that. At #6 it probably doesn't save much, but you could consider running bigger aluminum for not much increase in price for futureproofing.

System in process of purchase from SS:

(2) EG4 6000xp (12K)
(2) EG4-WallMount Battery (28.6K)
(28) Aptos 400w BF sub panel

The circumstances:

Utility Grid is backup only, after solar panels and battery storage (SBU)

Rural county property, 1500 sq ft house w/2 adults has outside 200a main electrical panel - Critical load panel 200a mounted next to main w/most circuits switched over to CL

Solar panels are in 4 strings in series, 7 per string, mounted as roof of carport, adjacent to 16' x 24' shed that houses inverters and batteries

80 ft distance between shed w/inverters and main/cl panels on opposite side of house

Grid & Load copper stranded wiring (6/3 NM-B plus gnd between inverters and CL panel, 80') mostly along joists in crawlspace with 11 ft underground at 24" outside house to shed. Wiring to run inside electrical PVC schedule 40 mostly under house and schedule 80 where entering and exiting the ground. (50 amp breakers)

Thank you, if you got this far, for enduring my whining. Just hoping I missed something!

 

[cs1234]

Well, I think we had a miscommunication, my fault for not mentioning the AC. I already knew that 10 was fine for the PV wire. Can I safely run 8 awg for the AC conductor loads at 80 ft? ...and the conduit fill limit is still out there...I was hoping 8 wires in 1.5 inner diameter PVC...?

It was my fault for completely ignoring huge parts of your original post. I focused on solar panels like some kind of fool. I'm not even sure why the solar panels and string configuration are mentioned in your original post. You weren't asking any questions about them at all.

 

[energyhunter]

How do you get 8 wires / 2 pipes? Do you mean L/L/N/G in both pipes?

12kW = 50A? Yes #6 is fine... except you mentioned 6/3 Romex which is kind of confusing because Romex is not rated for conduit installation outdoors. 6/3 romex is not enough if there is a possibility you want to pass 12kW from a grid tie inverter in the future, since those inverters require a 125% continuous factor, 1.25 * 50A = 60A, while 6/3 Romex can only carry 55A.

For #8. #8 THHN is fine for 50A but 8/3 Romex is not fine.

For conduit. Download a conduit fill calculator to your phone and start playing with it (I can open mine up, but it's probably easier for you to do it yourself). My guess without opening it is that 3/4 SCH80 can maybe fit 3x #6 CCC, 1x #10 EGC.

EDIT: OK, opened it up... 3/4 SCH40 can fit but 3/4 SCH80 cannot.

Regarding voltage drop. How long per day are you really going to be at 50A? Your batteries can only feed that for 2.5 hours, so you'll need solar output to be perfectly lined up... and if you have long running 50A loads you're likely to overload the inverter anyway.



Use aluminum where the cost starts to make sense is all I can say about that. At #6 it probably doesn't save much, but you could consider running bigger aluminum for not much increase in price for futureproofing.

I'm the patient, not the doctor: 2 inverters, each has load, grid and gen. I'm not using a backup gen for now. Load has red and black hot, white neutral and green ground=4 wires + the same for Grid = 8 (AC?) wires total per inverter x 2 inverters = 16 total. Assuming I can fit 1 inverter's load and grid into one PVC pipe conduit and the same for the second inverter, that's 2 conduits. Sorry, I don't know the "lingo" yet, maybe now you can extrapolate what I'm trying to suggest. I want to save money and not sacrifice safety. Also just my preference to stick with copper. Thank you zanydroid for responding.

 

[zanydroid]

Why don’t you stack (parallel) (combine the batteries and outputs) the inverters together? 6000XP allows it. It will be more convenient to plan out your loads and result in fewer wires.

If you for some weird reason want to keep it separate the various conduit and current capacity math will probably work out with #10 since the max AC amps on 6000XP is 25A

For the power levels here copper makes a lot more sense.

 

[energyhunter]

Why don’t you stack (parallel) (combine the batteries and outputs) the inverters together? 6000XP allows it. It will be more convenient to plan out your loads and result in fewer wires.

If you for some weird reason want to keep it separate the various conduit and current capacity math will probably work out with #10 since the max AC amps on 6000XP is 25A

For the power levels here copper makes a lot more sense.

I understand so far that I'll be 'paralleling' but, and please excuse my admitted ignorance, I'm not grasping yet how it will be fewer wires.

 

[zanydroid]

I understand so far that I'll be 'paralleling' but, and please excuse my admitted ignorance, I'm not grasping yet how it will be fewer wires.

I will use #8 here assuming you are using a wire type that allows you to load it to 50A.

You put the two inverters next to each other.

You combine the AC output together in a junction box or wire trough next to the inverter. Now this output circuit can be run as a single set of #8 rather than two sets of #10

For the input. The 6000XP is rated for 50A bypass. So you can directly feed two 6000XP (each with 25A output, for 50A inverter total output) from a shared 50A circuit without additional breakers to stay below the 50A of a single inverter.

It would be #8 from the 50A breaker to grid, to a splice that splits it to two sets of #8. Then each set goes to a separate 6000XP.

 

[jjww]

might want to look at conductor derate for more than 3 conductors in a single conduit-that will force you into a WAAY bigger awg

 

[zanydroid]

might want to look at conductor derate for more than 3 conductors in a single conduit-that will force you into a WAAY bigger awg

Yes, that is important but with 25A per circuit both #8 and #10 are fine with 2 or 4 circuits per conduit. 25A comes from the unconventional stacking config that I don’t think makes sense

If it is #8 for 50A circuits then it’s not enough even at 2 circuits.

#6 is good at 2-3 circuits in most ambient temps and good at 4 circuits in cool ambient temps

I am using the allowance to count L/L/N as two CCC on split phase systems.

(I’m not using a calculator/looking at derate tables so recalculate before using)

 

[energyhunter]

I will use #8 here assuming you are using a wire type that allows you to load it to 50A.

You put the two inverters next to each other.

You combine the AC output together in a junction box or wire trough next to the inverter. Now this output circuit can be run as a single set of #8 rather than two sets of #10

For the input. The 6000XP is rated for 50A bypass. So you can directly feed two 6000XP (each with 25A output, for 50A inverter total output) from a shared 50A circuit without additional breakers to stay below the 50A of a single inverter.

It would be #8 from the 50A breaker to grid, to a splice that splits it to two sets of #8. Then each set goes to a separate 6000XP.

Okay, the wire type I'll work out later, but I can see the wire reduction in a junction box, so I will have one set instead of two going to the output (LOAD/CL panel.) I will need to draw up a schematic to better understand the input portion. It's after midnite eastern time so I will revisit this tomorrow (later today) and let you know when I've been educated. My son has the same system so I will get his input on the input..bad pun. Thank you zanydroid.

 

[energyhunter]

might want to look at conductor derate for more than 3 conductors in a single conduit-that will force you into a WAAY bigger awg

I will check this out, thanks jjww

 

[1201]

Go bigger than you think you need. It doesn't cost much more to future proof now.

How much is 80ft of 2224 aluminum wire?

 

[energyhunter]

Yes, agreed, thank you 1201

 

[energyhunter]

Go bigger than you think you need. It doesn't cost much more to future proof now.

How much is 80ft of 2224 aluminum wire?

Not sure, but I can tell you that the following is $304 for 80' (maybe zanydroid can tell me if this is the wrong wire type)

Cable Cabana 6/3 NM-B x 80' Non-Metallic Sheathed Electrical Cable with Ground​

https://www.amazon.com/s?k=6%2F3+NM-B+x+80%27+Non-Metallic+Electrical+Cable&i=industrial&crid=MQT4GU4NPVA&sprefix=6%2F3+nm-b+x+80%27+non-metallic+electrical+cable%2Cindustrial%2C150&ref=nb_sb_noss

 

[1201]

How about

Amazon.com

 

[zanydroid]

Not sure, but I can tell you that the following is $304 for 80' (maybe zanydroid can tell me if this is the wrong wire type)

Cable Cabana 6/3 NM-B x 80' Non-Metallic Sheathed Electrical Cable with Ground​

https://www.amazon.com/s?k=6%2F3+NM-B+x+80%27+Non-Metallic+Electrical+Cable&i=industrial&crid=MQT4GU4NPVA&sprefix=6%2F3+nm-b+x+80%27+non-metallic+electrical+cable%2Cindustrial%2C150&ref=nb_sb_noss

6/3 Romex is going to cause various kinds of grief with conduit b/c it's not rated for outdoor use and it is hard to pull through conduit/needs an upsized conduit.

Also that's a funny brand name.

Not super familiar with direct burial aluminum (we have tiny lots here so if you have a lot big enough to worry about it, you are wealthy enough to not DIY) but maybe this:

2-2-2-4 Dyke Aluminum Quadruplex URD Direct Burial Cable

2-2-2-4 Dyke Aluminum Quadruplex URD Direct Burial Cable

www.wireandcableyourway.com

$1.80 per foot. #2 is good up to 90A

The cable choice is complicated:

URD, USE, MHF inside a building

I will have about a 50 foot run underground from the house to my subpanel, using 2-2-2-4 aluminum wire. I plan to run the buried URD up the exterior garage wall in conduit, then through a 90 where it penetrates the wall. I could come through the wall relatively low, and then turn and come into...

www.garagejournal.com

You can get various kinds of #2 cable from electrical supply houses locally to save on shipping. It is huge and heavy. Usually they will sell by the foot.

 

[energyhunter]

Thanks for the aluminum wire/cable info, zanydroid. As an aside, when I retired several years ago I discovered that my new "job" was all about saving money on my necessary purchases. Also I prefer DIY when possible because I get an education that may continue saving us money in the future. Also I get to keep most of the tools when I'm done with each project. Thanks for contributing to my education.