Need Advice on small Grid Tie setup

wilsonbh

I'm finally going to pursue setting up a small grid tie system.  I can only accommodate about 10 panels so I was thinking of 320w panels for a 3.2kW system.  I'm confused however about using micro inverters versus a single inverter.  Is there any reading here I can learn from?  Anyone have any advice on how to proceed? 

Billy

wilsonbh

Wow! This is a GREAT site.  I've learned a lot here.  With the price of solar going down, I'm anxious to install my own system.  I wish there were some detailed plans somewhere that I could follow.  Anyone know of any?

Billy

Merritt Island, FL

wilsonbh

BTW, I'm listed as a "SOLAR EXPERT" but I'm no expert.  Would best label me as "SLOW LEARNER" versus expert.  I've been coming here for a long time.

BB.

Are you going to install this yourself, or with an installer?

What about building department rules? While a single/central GT inverter has advantages (one thing to repair/replace on the side of wall, installed out of direct sun/rain, etc.)... There are new(er) solar installation codes which are making distributed micro-inverters easier to install code wise.

Basically, with solar panels, they are "current sources" that normal circuit breakers will not trip if there is a short circuit. And DC sustains arcs better than AC (if you have a wire break). With central GT inverter, you have a bunch of DC wiring that is more susceptible to short/open circuit fires/arcing. If you install micro inverters with 1 per solar panel, you are converting from AC to DC on a per panel basis--And runing 240 VAC on the roof to your main panel. This can be a "safer system". Central GT inverters have code requirements which can be a pain (depending on your building code agency).

https://www.youtube.com/watch?v=Zez2r1RPpWY

There have been roof / system fires because of this (rare, but does happen).

And lastly, double check that your utility is still supporting GT Solar power system connections. Some never have allowed, others are starting to pull back (less subsidies for user), and even preventing new installs.

There are a lot of questions that depend on your location and regulatory requirements.

-Bill

wilsonbh

Yes, I live in Florida and want to install this thing myself.  Florida Power and Light allow for GT setups.  My only hesitation is how is the best way to do this.  I want a simple system with as few single point failures as possible and although the micro inverter approach seems like an easier way to proceed, seems to me that the heat here in FL will reduce the lifespan of these panels, not to mention the prospect of a fire.  So I'm bending towards a GT with a single inverter but still haven't 100% decided. 

I want only 10 panels to be on the top story behind my fireplace.  This picture was taken early in the morning so it shows more shade than it normally gets.  I routinely get 8+ hours of direct sun on this top level.  So hoping for 320w panels and possibly a Sunnyboy or Xantrex GT inverter.  I have a standing seam metal roof so I need some special connectors for the panels.  Should be a pretty easy install.  But then, nothing is ever as easy as it seems.

BB.

In general, with shading, micro-inverters may be a better choice. Just a simple power line shadow across one panel can kill upwards of 1/2 of the array's output (depends on a lot of details, but this is not an uncommon "derating" for central inverter installations.

And if your shading is tree/plant based--They will grow overtime. So you may have to take out some favorites, pay for ongoing trimming, or if it is on a neighbor's property--"Living" with the increasing shading (I have a redwood in the yard behind me--It is not getting any smaller).

The newer generation of micro inverters are probably better designed, less impacted by heat... Obviously, if one fails, you need to go up on the roof and pull up the failed panel+unit (possibly several panels to get there).

In general, you should do a paper design for both setups and see what works out best for you.

For Florida, did they not require licensed installers for GT solar?

Also, find out what your building department allows--There have been some new roof access requirements (by fire departments) that is making roof installations a bit more difficult (and limiting allowable roof area for panels).

-Bill