Size of inverter to meter wire

[Jallister]

Hello! Im new to the forums, and hope to get to know you all better.

Right now, Im trying to figure out what size wire I need to run from my inverter, to the meter, and was hoping you guys could help me cipher out the details.

Im setting up a 7kw system with 26 Canadian Solar 320P Solar Panels, installing SolarEdge P400 optimizers, and using a SolarEdge SE7600A-US inverter, and wiring it up for 2 strings of 13.
I want to upgrade the system to a 14kw system at a later date, so anticipating that, Im trying to run the AC from the inverter to the meter to include future expansion.

I have two different locations that I can place the system. One would require running the AC cable 400 feet, and one would require running the AC cable 600 feet. Until I find out if the building can take a three phase hookup, I would have to assume 240v single phase.

Im not confident with the figures and formulas. The best I can come up with is 2/0 wire. Any help would be appreciated, and thanks in advance.

[SunEagle]

Hello Jallister and welcome to Solar Panel Talk

To help us understand your question a little better maybe you can tell us where you live and what electric code you need to meet.

Also what does your POCO require to connect a home/business solar PV system to their grid?

[Jallister]

Thanks for your reply, SunEagle. Im just looking for the wire size that will give me less than a 1% drop, assuming max on my inverter.

[Mike90250]

7Kw is a pretty large system, and 14Kw is over the top, since in USA, over 10Kw falls under commercial rules, and for 14Kw, you will need an upgraded main service & panel.

Generally, the longer run is done with the higher voltage system, either the 450VDC solar, or the 240VAC inverter. Sometimes, long 240VAC inverter runs have enough resistance, the voltage rises and shuts the inverter off.

[SunEagle]

Well the SolarEdge SE7600A should have some good documentation concerning the recommended output wiring based on the amperage and voltage. There are also some easy to find voltage drop calculations that will give you wire size based on current and distances.

But... the maximum size of the breaker that back feeds the solar power into your panel is determined by the main panel buss rating. And if you need wire bigger than what that breaker can handle due to a voltage drop issue you will not be able to increase the size of the breaker to accept the larger wire size.

My estimate for the SE7600 is probable around a 40A CB which would normally be about a #6 wire. A #2/0 would never fit into a 40A CB. So I am not sure how you would be able to run the bigger wire now and land it on the smaller CB or if your panel would even be able to accept 14kw or 80A of solar sometime in the future.

That will require you to work with your POCO to get a variance of some kind.

[Jallister]

The utility company has the requirements set up in tiers. It's a rather simplified process for the two tiers lower than 20kw. 7kw is the first tier, and rather simple, by the looks of it.

The property is zoned light industrial. I've got two separate buildings on the property. One uses approximately 4,000kwh/month, the other about 800kwh/month.

There is an awesome spot to put up a 20kw system up next to the small building, but energy production would exceed its use, and then I would have to get contracts and crap for the PoCo to buy the excess. To run it to the other building, would require the energy to travel 600' to the meter.

The closest I can get it to the big building, would be in a place that would stifle further development, and still leaves the array for a 7kw system 100' from the meter. Expanding the system later would require placement an additional 200' (300' total) away from the meter.

Getting a 20kw array into the small building would require about 100'.

I own the two different businesses that occupy both buildings, and pay seperate utilities for them. Has anyone ever heard of the PoCo crediting a seperate meter than the one being supplied with excess power?

[foo1bar]

I own the two different businesses that occupy both buildings, and pay seperate utilities for them. Has anyone ever heard of the PoCo crediting a seperate meter than the one being supplied with excess power?

Yes - it's often called "virtual net metering".
You'll have to check if it's available in your location (doesn't exist in all states, nor all POCOs)
You can try searching "<POCO> virtual net metering <STATE>" and see what you come up with.

600' is still doable I think for running wire - it's going to cost you a fair amount for some large aluminum wires, but I think possible to do.
Electrician might be able to tell you if doing a transformer at each end would actually be cheaper. (or if there's another cheaper option)

Also depends on what kind of power you've got - 240V single phase like a house? Or a 3-phase? (since it's industrial area, might be 3-phase and might even be high-leg 3-phase )

[Jallister]

I'm hoping that it's three phase. I'll keep my fingers crossed and check out virtual metering too. Thanks!

[Jallister]

And ... They do! Awesome. That'll save a bundle. Thanks again!

I'll keep you posted of my progress.

DTE Michigan, by the way.