Installation Chronology (Overview)

"There's only one way to do things correctly, and a whole bunch of ways to do things wrong." -Catfish, Installer

Catfish, our imaginary installer, knows the right way to start a project.  In fact, he's self-considered to be right about everything all the time!  So, if you arrive at someone's doorstep for the first time, and they've never met you before, and all you have are a bunch of photos of their house and the system design plans, what is the best way to go about performing an installation?

1.  Consult the Property Owner and Confirm Plans
Walk with the homeowner to every part of the house and show them, physically, where you plan on mounting the inverter.  Make sure they verbally OK it with you.  That way, they can't, in good conscience, complain and say they wanted it elsewhere later.  Then, explain the path you will run the conduit.  Ask if they had any special considerations.  Ask where the bathroom is, and tell them that you and your installer crew will need access to it during the installation *unless they want to give you guys a porta-potty, which is unlikely.  Make sure they see the roof layout so that they know how many panels, and roughly what it's going to look like.

2.  Set Up Safety Equipment and Ladders, Mark Out The Roof.
After they are entirely on board with the plans, then begin to set up your ladder and harnessing equipment with the work crew.  As a lead installer, you should oversee the set-up of all safety equipment, and even the placement of the ladder can be considered part of your responsibility to ensure safety.  Once the ladder is set up, mark out the roof with a crayon, to determine the position and length of the rail.  I have a special set of symbols that I recommend.  Use the same symbols so that people don't get things confused.

3.  Construct the Conduit Run.  
If you are working in 2 teams (a roof crew and an electrical crew), and you're the lead installer, it's likely that you will be doing the electrical work, and the other guys will be doing the structural stuff.  Don't start your conduit run on the roof just yet, because if you mess up and it ends up not where you want it to be, either directly in between panels (obstructed by the frames) or outside of the array, it'll be very difficult to cover up the mistake.  Begin making your conduit holes into the house at the point where the conduit will be entering and exiting the structure, depending on your plan.  Start anywhere you want, but step 1 is building the conduit run while the roof crew starts finding rafters and marks the placement for the footings.   Complete the conduit so that it attaches to the disconnect in the basement, or to a wiring trough.  Check with the guys on the roof.  By now, you can determine a suitable place to complete the conduit run through the roof.  Pilot into the attic with a long bit, trying to find a point just far away from a rafter that you can drop your conduit into the roof and fasten it to the inside of a beam.  Check the position of your pilot hole from inside the roof to ensure that it will work with the conduit run.  Adjust, if necessary, sealing any pilot holes that you should make.  Use a flashing (see a more detailed look at this procedure).

4.  Construct the Mounting System (residential roofs)
Assuming you're installing on a traditional roof, and you have a team of trained workers, this by now must be routine to you.  Read [here] if you want a more detailed look at this procedure.   Make sure that you are using the correct number of footings.

5.  Wire the Roof
This is where experience really becomes necessary.  You have to map out the positive and negative ends of each string.  You also need to ground everything.  Make the USE-2 wires long enough to reach where they're going to connect to the panels, and then also long enough to make it into the combiner box with enough extra length (but not too much length) to connect to the parts inside the combiner.

Connect the wires to the parts inside of the combiner box, and add the MC-3 or MC-4 connectors necessary on the roof to connect the wires to the panels.  Make sure that you're using bare copper #6 on the roof, and connect it either with a copper split bolt or a irreversible crimp as it exits the conduit LB that is sticking out of the roof.  Follow the rules of grounding!

6.  Pull Wire From Combiner In Attic To Disconnect In Basement
I came to a point where I wasn't really using "combiners" to make parallel connections, because I found there to be less voltage drop when using multiple #10 conductors rather than fewer larger conductors, in most cases.  Still, it made sense to have a J-Box near the roof, just to transfer the wire types from USE-2 to a more conduit-friendly type of wire, namely THHN-2 or similar.  In any case, connect all the wires all the way from the roof to the basement.  "Tie in" the wires to the terminals in the disconnect, all the way to the inverter.  Follow the rules of "grounded conductor wiring."

7.  Wire the AC Side.
If you have a PV License in Connecticut, technically you're not permitted to perform this part of the installation, and you really shouldn't because your test didn't cover even the basics of AC wiring.  So I'm not going to get into the details of this.  The basics are that it goes:  Inverter, meter, outside disconnect, service panel.  If there are multiple inverters, then it goes inverter 1 / inverter 2, subpanel, meter, outside disconnect, service panel.  Don't even ask about lineside taps.  You can use double-insulated (romex) wire for this part of the installation because it's after the inverter, no longer DC current.

7.  Complete the Wiring and Perform A Preliminary Visual Inspection
Make sure that everything is connected, and everything is off.  Perform continuity tests if you wish.  If you are thorough, there shouldn't be any problems.  It's infinitely safer to complete all the wiring (and also adherent to the NEC code) to make sure that all of this has been done entirely before wiring panels, because once a string of panels has been installed, the wires become live and there's no way to really shut it off.  Make sure all your fuses are in, and be sure that you are using the right fuses (see panel specs for that information).

8.  Prepare and Install the Panels
Always last, but never least.  This should always be the final stage of your installation.

Here in the early part of the 21st century, we haven't figured out not to use conductive metals on the roof, so even the panel frames are aluminum and need to be grounded.

To prepare the panels, use an anti-oxidation gel (like "nolox" or some crap like that).  Fasten each nickel-plated beaver tooth ground lug to every panel, using a stainless steel screw, a washer that will bite into the paint of the frame, and a nut behind it to keep it in place.  That's the official way to do it, according to all the grand-daddys of solar such as Bill Brooks and John Wiles.  Add stainless steel "S-Clips" as well, to keep your panel wires from touching the roof.

As you connect the panels, follow the map that you made in step 4 (if it's not soaking wet or torn into pieces or somewhere in the van).  If it's a complicated roof and you lose the map, there will be trouble!  Be careful, stay roped in.  Once the roof is complete

Following This Order
This manner of conducting installations will provide you with the least number of problems with things not timing correctly.  There's no better order of chronology.  This particular order of things keeps both the roof crew and the electrical crew working in tandem.  It makes everybody available for panel time (all hands on deck) and leaves nothing left over once the panels have been installed.

Installers:  Any tips, suggestions, questions, disagreement, or otherwise?  Please say.