question

@SAMS VANS, if your terminal is scorched or burned then you had a loose connection; your PV will not cause this, only failure to fully tighten the terminal to begin with or the terminal may have loosened over time if the installation is in a van or other installation subject to a high degree of vibration.

One thing I have seen in some installations is that the wire insulation is not fully stripped back and so the terminal is tightened onto the insulation rather than the wire; this faulty connection will cause arcing and heat at the terminal and, eventually, device failure and possible significant system damage.

As a side note, it is inadvisable -and in fact specifically advised against- to connect mismatched panels to a single controller. If you have a 100w panel and a 170w panel, each panel should be connected to its own controller.

THANKS JUSTIN. YES I DO BELIEVE IT WAS CAUSED BY LOOSE CONNECTION. I NEED TO KNOW IF EXTRA WATTS FROM SOLAR COULD BE CAUSING CONNECTION TO LOOSEN AS IT IS RATED BY SPECS AT 220W AND I HAVE 270W. I KNOW CONTROLLER WILL NOT ALLOW OVER CHARGING EITHER WAY , BUT MAYBE IT CAN NOT HANDLE ETRA HEAT CAUSIN TERMINAL TO LOOSEN. HATE TO REPLACE AND NOT ADDRESS UNDERLYING ISSUE. ALL TERMINALS WERE INSTALLED WITH GREAT CARE IN AND TIGHTENED AND CHECKED 3X OVER.

@SAMS VANS, no, the addition of the mismatched panel would not cause the PV input terminal to overheat unless the wire itself was overheating, so if you're certain that your connection at the controller is good, you should check the system wiring on the PV side to ensure that you don't have a loose connection elsewhere. The 75/15 will not accept 8AWG at its terminals (maximum 10AWG) so either your wiring is different than you think it is, or you've trimmed strands from an 8AWG cable to get it to fit into a 10AWG terminal, in which case you could easily have a runaway strand that is arcing or some other very dangerous condition.

You should not run those mismatched panels into a single 100/20; as noted in my original reply, mismatched panels should not be connected to a single controller. Rather, you should put each panel on its own 75/15.

Also, as a moderator here and in the interest of furthering the knowledge base for others who might have this issue, I have edited your original post to make your questions clear and to remove the ALL CAPS. Please refrain from using all caps in the Community, as this makes the information and questions incredibly difficult to read, which makes it difficult for myself and other users to assist you or to find pertinent information in the future.

Panels are wired parallel?

Sorry I am new to this. The wire is 8AWG five strands of wire were clipped at termial connection as directed by the dealer/designer (AM SOLAR). Heat shrink was then placed over the wire, terminal depth was measured and wires were stripped accordingly. The connections are all good. Still wonder if PV+ is getting hot and causing expansion / loosening of wire at terminal over time. And if going to larger mppt would fix problem. I was told mppt 100/20 can be used with 290W solar array and tech manuals confirm this. Solar array is wired in parallel as directed by dealer.

Yes all connections are good. Contacted dealer and they assured me that although it may not be advisable to mismatch panels all the math has been done and panels are safely / correctely wired to the MPPT. My original problem is that yes PV+ became loose at mppt. Would the excess watts of solar array cause this to heat at terminal and loosen over time? And if so would going to larger mppt 100/20 which is rated up to 290w solve problem? Original

mppt was the 75/15 which is rated up to 220W.

AM SOLAR still takes the position that they stand behind their electrical sytem design/wiring. I have ordered a new charge controller and will be reinstalling with extreme attention to detail and monitoring the connections on a regular basis. If this problem should arise again the future I think I will be replacing the wiring between solar roof penetration box and charge controller. Thanks for all your help and knowledge in addressing this problem.