Three phase Solar Power for commercial use

3 Posts
Oct 1, 2008 03:00 pm
Three phase Solar Power for commercial use

Hey everyone,

I'm currently designing a three phase solar power system for commercial use. I've pretty much decided on using (24) Kyocera KD205GX-LP panels, (3) Fronius IG 2500-LV inverters, (3) Delta LA602 DC Lightning Arrestors, (1) Delta 303R Three Phase Lightning Arrestor, (1) Square D AC Disconnect DU321RB. I'll also need a panel to combine my three inverters.

There are a couple of things I'm unsure about.

How I'm going to mount it for one. We have one south facing roof but the angle of the roof is no where near optimal. We do have a ton of land if I wanted to do a ground mount and the location would be impossible for vandalism or theft.

Code is another portion. I don't know if the disconnects contained within the Fronius inverters are up to code. I know that I will need a disconnect capable of being "Locked Out" per OSHA rules on the AC side but I'm not sure about the DC side of things. Going along with code, how would I ensure that all of the equipment is properly grounded.

I'm very confused by grounding the equipment. I've read the NEC Code about 10 times and I'm just confusing myself. Can someone give it to me in Laymen's terms.




My plan is to wire 8 panels in series to each inverter, then have each inverter wired to my "AC combiner panel" which following the directions Fronius gives to wire in 3 phase. Then I'd run my three phase power from my "AC combiner panel" into my AC Disconnect and from there into my main panel. The only other question I have is where do I need fuses/breakers other than where I connect to the panels?
 
3 Posts
Oct 24, 2008 11:13 am
Re: Three phase Solar Power for commercial use

Does anyone have something to say?
 
163 Posts
Oct 24, 2008 12:35 pm
Re: Three phase Solar Power for commercial use

Adam,

The best thing for you to do is consult a professional who will have experience with both solar and commercial power systems. I think most people here are more familiar with the basic home power.

Having said that, in really simple terms all equipment must be grounded, all grounds must be connected together, and neutral and ground must be bonded at one point, and ONE POINT ONLY! Assuming that you already have commercial power this should already be done, so you should not be bonding neutral to ground anywhere in your system.

The State of California is very forward looking in terms of solar and also the protection of their citizens. For example, I believe that any inverter sold in California must now be offered with at least a 10-year warranty. They also test and approve all equipment before it can be sold.
http://www.gosolarcalifornia.org/equipment/inverter.php

From the above list you will see that there are much larger and more efficient inverters available on the market for 3-phase power systems. It's your system, but I would give consideration to going with a single high efficiency inverter with a 10-year warranty that could handle all of the panels rather than what is essentially three separate systems and then combining them.
 
351 Posts
Oct 24, 2008 01:10 pm
Re: Three phase Solar Power for commercial use

Great response John B.
The only thing I can add is that given the option between a roof mount and a ground mount, I always choose the ground mount.

Ken
 
578 Posts
Oct 24, 2008 02:35 pm
Re: Three phase Solar Power for commercial use

what is the voltage? 208? 277? something else?  i am thinking 1 larger inverter may be easier than three small ones.  if we know what the panel voltage is, I can find some inverters that will match.

james
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578 Posts
Oct 24, 2008 03:13 pm
Re: Three phase Solar Power for commercial use

for example, the sma 7000, can do two strings of 14 modules.  1 inverter solution that can do 277 or 208 voltage systems.  you would prob use square d h362rb and du221rb (think those are right part # by memory) for the disconnects to satisfy any inspector [visible, lockable,  . . .]

fronius is great too, but 1 inverter decreases the balance of system gear that you need and also can put you into one backfed breaker instead of 3.

hope that helps,

james
altE staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
3 Posts
Nov 5, 2008 01:02 pm
Re: Three phase Solar Power for commercial use

The main panel that the system will be tied into is 120/208V. I'm not too worried about how difficult it will be to install anymore. We've decided to use the Solectria 13kW Inverter which is designed for three phase power. It will make things a lot easier and allow for much more expansion in the future.

My only questions now are on the NEC Code.

Using 12 Kyocera 205W panels, I have an Voc of 398.4V and Isc of 8.36A. These values are the rated values of the panels with no correction factors used. If I did my calculations correctly, then I would use two #12 and one #12 GND copper wires for going from the solar panels to the inverter which will be about 200ft away.

Then from the inverter to the panel, I came up with three #6 and one #8 GND for going from the inverter to the main panel which is about 10ft away.


Are these calculations correct? The inverter will be outside and already includes code compliant AC & DC disconnects.

Conduit size for both runs I'm unsure about as well.

For the run from the panels to the inverter it will be buried but from the inverter to the main panel would be above ground.

Thanks for the help so far!
« Last Edit: Nov 5, 2008 01:07 pm by Adam Cu »
 
163 Posts
Nov 5, 2008 04:15 pm
Re: Three phase Solar Power for commercial use

Adam,

If you're running the output from ~2500watts of panels to a 13kv inverter I would make sure that the conduit is large enough to add four more stings of the same panels to take the inverter up to full power.

Compared to the cost of your panels, the cost of conduit and 600 feet of copper wire is negligible. I personally think 200 feet is quite a long run for #12AWG and would go with #6AWG to minimise line losses. A larger conduit makes it easier to pull wire, so I would go with the conduit that matches the largest knock-out at the inverter end and you never have to worry about it again.

John
 
1 Posts
May 3, 2011 12:00 am
Re: Three phase Solar Power for commercial use

What are those phase? Sory, just being cross in here. Thanks for guiding to here.! Solar Power Queensland
 

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