[no1dc]

Well been busy with solar installs. Let me say me and schematics are about as close as New York is to San Francisco. With that being said here's my situation.

I completed my solar install at my office, 4.5Kw system. Had a local building contractor friend do the electrical wiring. I depended on him to give me the right information concerning the wire and size needed. He told me I needed 12AWG wire to run from the solar panel array juction box to the aggregate panel. Two runs approximately 15' of 12/3 solid copper wires. I've been trying to find out from the solar designer if that is suitable to use at home for my runs 60+ feet. He recommended I use what he designed.

Look over the designs and #10, #8 THWN is called for and #6, #8 solid bare ground wire. So it got me thinking and I looked at the schematics for the office and #10 is called for where I used 12 solid copper and #10 USE-2 was used for ground where he had #6 bare being used.

He mentioned voltage drop was the reason to use the #10, etc....

So I've asked if the office install with the short run of 12/3 was ok, not heard back yet.

According to my home schematics it looks like I'm going to need 350-400' of #10 THWN in red, green, black, and white and #6 bare copper and #8 bare copper. Where would be the best place(most economical) to purchase this quanity of wire. Probably need 200' of #8 and 50' of #6.

Just got the ok for home today from KCPL and I'm trying to get everything purchased before we start the install. Solar panel and associated is waiting in CO to be delivered when I tell them I'm ready. I've got 6 months to get this up and running and approved for rebates.

Any advice would be appreciated. TIA Pete

 

[Dean]

I can buy most wire at Home Depot cheaper than at my wholesale house.

 

[Kaizen]

What voltage is running through those cables? If you get that we can converts killowatts to amps. 4.5kv dc at 48 volts is over 90amps. I know in ac 12 ga will handle 20 amps. hopefully we have a solar guy here to tell us those rules are different for some reason. He might have used the 2 12gauge for a dual breaker.
for your house it comes down to voltage, ac or dc, and how far the run is and maybe load?

 

[jac]

I was told any run over 50 feet needed 12 gauge with 20 amp,use 10 gauge for my 220 A/C

 

[twotone64]

For prices, I would just call around. Call the commercial electrical shops, home depot, your local hardware store, etc. Tell them all, that you are looking for the cheapest place to buy from, some will change their prices.

 

[Bluegoose1970]

To keep it very simple, your system designer is correct in his wire sizing, and not to follow his design MINIMUM standards or installation instructions you are not code compliant and negate any liability of the manufacturer or the approving agency (UL) which is also a code violation.
National Electric Code is a minimum standard to insure fire protection, not to be use as a design standard, which basically means it should not catch on fire but it does not insure that it will work. To make it work, you have to design it for the application and conditions that are present.

If you can't tell this is my trade and I normally refrain from this but just for educational purposes not related to anything you are doing, or any recommendations for your application. Heck, without a lot more information, I would be guessing.

Again follow the manufactures installation instruction and design, they normally give you the minimum standards needed to be met. It is up to the installer to upgrade these to the conditions that are present and the authority having jurisdiction to approve the installation. Do not deviate from the type of insulation required or sizing of the conductors unless it is an improvement or it is expressed in their instructions for certain conditions.

To keep you and your property safe and insure your installation is correct, I would consult with a qualified person in this type of installation in your area.

Its no different then a car electrical fire, wrong fusing and no access to the battery, it just doesn't stop.