Wiring up micro-inverters into household wiring

[skid]

I have 9-600watt inverters that output 120VAC each. Each inverter is directly fed 36VDC from 2-300W solar panels with MC-4 connectors. I have 120VAC wiring (4mm2 cross section which is equivalent to 12 gauge wire) with end plugs that match the inverter 120VAC input/output plug that can connect 3 inverters in my configuration. I also have wires that match the inverter output plug which has a standard 120VAC male plug on the other end which is meant to plug into a house receptacle.

When I built my house I pre-wired the attic with 10 gauge wire on a 30amp breaker. How should I tie in these inverters to this 10 gauge wire? I will have 3 rows of panels on my roof so will have 3 120VAC cords to connect to my house wiring. Do I need to fuse these? Is there a combiner box meant for this? What is the best practice?
Thanks

[frackers]

Depends on the manufacturer & country regulations.

The normal connection for an Enphase system for example is for all inverters to directly connect to an Envoy data collector so that the 'data over mains' work reliably. That connection when goes through an isolator switch AND a breaker before joining the house wiring.

Country reg will specify isolation requirements - where I am there must be full 2 pole isolation (i.e. live AND neutral) along with breakers and signage on the main panel that indicates that there is an alternate energy source, where it is and where the isolation switches are.

Main consideration is to not fry a linesman up a pole due to a faulty inverter (e.g. not shutting down when grid disappears).

[skid]

Thanks Fracker,
I'll wire it similarly to my water wheel which has a isolation switch before going into a breaker. The inverters are anti islanding as well.
I guess my question is how to wire the smaller gauge inverter leads into my 10 gauge wire. Your supposed to set breaker size according to the smallest wire size which is 12 gauge out of the inverter daisy chain. I don't want to de-rate the breaker if I don't have to which is why I mentioned fuses.

Now that I think of it I can set up a small sub panel fed by the 10 gauge wire. I already have a spare subpanel I could use for it and just need to buy 3 20 amp breakers for the 3 inverter leads. Thoughts?

[Mary B]

I would have each inverter on its own breaker depending on electrical code where you are at. And THAT is what you need to go by! If you don't your homeowners insurance will be null and void in case of a fire no matter what the source. Insurance adjusters will look for anything they can use to screw you out of being paid!

[WindyOne]

You should have a Dedicated PV Circuit Breaker in your Mains Panel, only for the PV Input.
And the Dedicated PV  Breaker must be located in the proper slot within the Main Panel.
9 x 600 watt inverters = 5,400 watts <<< WOW !!!
5,400 watts / 120 v = 45 AMPS <<< YIKES !!!
And you only have 12 gauge wire and a singe 30 amp breaker?

You are NOT allowed to connect all nine (9) inverters to that single circuit.
You are allowed to connect only four (4) maximum of those Micro-inverters to one 30 amp breaker.
Worse yet, you are allowed to connect only three (3) maximum of those Micro-inverters to a 12 gauge cable.
You need to consult with a local electrician, asap !!!

[skid]

I missed reading your post Windy One, which you also misinterpreted. I have a 240V/30A breaker which is good for 7200 Watts, using 10/3 wire (2 - 120V/30A leads).

Anyways, I just finished installing the panels and wiring everything up. I ended up doing something a bit different. I have three buildings on my property; our main house, a carriage house/garage, and another outbuilding.

- I installed 14-300W panels and 7-600W inverters on the main house. I ran 2 dedicated 12 gauge cables on 20A/120V breakers. One line has 4 inverters plugged in, and the other has 3. The capacity of each line/breaker is 2400W so it matches the maximum rated output of the 4 inverter set of panels/inverters. In reality the maximum output of each panel set/inverter is quite a bit less than 600W. The most I've measured is ~500W at noon  on a cloudless day.
 
-On the outbuilding I installed 4-300W panels with 2-600W inverters and tied it into a 120V/20 amp (1800Watt) dedicated circuit.

- The carriage house/garage has the 10 gauge wiring/circuitry I noted above. I haven't installed panels yet on this building because of access issues. The roof has a steep pitch and is quite high off the ground so I need to set up scaffolding when I eventually add panels to this building. At some point I'll add another 16-300W panels to this building, as that's how many I can easily fit.

Interestingly, I  measured the output of a very slightly dust-covered panel, then immediately cleaned the panel with water and a scrubber. I squeegee'd the excess water off and re-measured the output. It gained over 10% output! So keep those panels clean!   

[SparWeb]

I'm a bit late to come and tell you what to do, I guess...

I remember discussing your grid-tie setup with you but it was a long time ago.  IIRC you already have a grid-feed in through your inverter.  You haven't mentioned how the new solar panels will connect to that part of your system.  This is just curiosity now: your Poncelet wheel that feeds the grid-tie inverter does that connect to the grid on a separate branch at your utility connection point?  Or do you have branches, say, from the house to other out-buildings and the house has the inverter?

I'm just trying to picture your system now that you've mentioned the garage and carriage house.  It sounds a lot like mine, where I have a garage and a shop plus my house, each on a separate branch going in different directions from the utility pole.  Each building has its own "primary" breaker panel.  So my curiosity about how you arranged your various buildings is purely self-interested, you see

[skid]

The waterwheel has its own dedicated inverter which feeds directly into my 200A/240V panel in the house via a 30A/240V breaker. The solar panels have mini inverters (600W/120V) that also feed into the main panel on 20A/120V breakers. So everything goes into the main panel. What isn't used by us gets measured by a smart meter and pushed out into the grid where we make a whopping $0.10/KWH

[SparWeb]

You could be a hundredaire next year!