Installed PV system questions

calitundra

I have a 33 panel system with REC 235PE panels. They each have a Tigo monitoring system which is then fed to a SMA 7000 watt inverter.  I have had this system for about 3 years.  My installer bailed on me so I have been working on the system myself.  I have had a few modules go out but Tigo has been good about sending me replacements.  Anyhow every year my annual bill increased from about $100 to $400 and now $800.  I have been putting more thought into this system and notice, per Tigo, my panels don't produce more than 180W peak but more around 160w.  The voltage is about 25 volts per panel.  I contacted REC and they said if i plug into them directly with a meter and they are less then 30volts they would replace them.  They are all doing that so I am thinking it is not the panel.  Tigo said it may be the SMA inverter programing? but I don't see any information on how to program it.  Each panel, per Tigo, is producing around 5 to 6 amps.  3 strings of 11 panels each.  I looked at the wiring to the stings and the installer has 10ga wire.  If that is correct that would be about 55 to 66 amps per string.  It is about 100 feet from the panels to the inverter.  So now is the wire to small?  Is the inverter need to be programed?  Are the panels bad?  I don't know where to start.  I tried using the calculator because I though maybe the wire was choking the system but just adding the amperage and distance doesn't seem like the 10ga is right?  Lastly the system runs at about 260volts DC to the inverter. The panels are facing primarily West. Any help would be appreciated

John

vtmaps

calitundra said:

Each panel, per Tigo, is producing around 5 to 6 amps.  3 strings of 11 panels each.  I looked at the wiring to the stings and the installer has 10ga wire.  If that is correct that would be about 55 to 66 amps per string. 

Welcome to the forum,

I am off grid and don't know much about SMA programming, so I can't help you there.  

When panels are in series, their voltage is additive, but current (amps) is not.  Thus 11 panels in series would be 5 to 6 amps at 11 X 25 volts = 275 volts.  When in parallel, current is additive, thus 3 strings in parallel would be 3 times 5 to 6 amps = 15 to 18 amps at 275 volts.

--vtMaps

Dave Angelini

The wiring sounds right. Download the SMA manual (which SMA 7000 model?)  and start learning the screens.  You need to be able to understand what it is telling you and communicate it here. As vtmaps said the math looks good. You might look into obtaining a clamp-on DC ammeter as you are probably going to seperate the strings and measure each one after you can tell us how much power each day is being harvested and if it is stable. Stable because when there are problems like this it can be intermittent.

Hey vtmaps! How are you? had some weather?  --Dave
https://earth.nullschool.net/#current/wind/surface/level/equirectangular=-105.00,0.00,256/loc=149.361,-66.808

vtmaps

Dave Angelini said:

Hey vtmaps! How are you? had some weather?  --Dave

No weather here... too far inland.  There's some weather on the NH and Mass coast.  --vtMaps

Dave Angelini

Nice!   I thought I remembered you were not on the coast. 

Marc Kurth

Dave - thank you for that map!

Dave Angelini

You are welcome! My brother is a Navy pilot and he uses it all the time.
Looks like some good times for the caribbean forming off africa. Might even head toward you, might not is better
Happy Equinox!