Solarline parallel connectors

bethbeth Solar Expert Posts: 32
Where are the Solarline parallel connectors normally used?
Can you use these to parallel two strings together before the combiner box?
For example if you had strings of two (24V panels at 8 amps) that you were
running into a combiner box then to a mppt. controller, could you use these connectors
to parallel two of these strings at the panels and reduce the wiring running to the combiner
box and cut the circuit breakers needed in half? This is assuming that you
stay within an allowable distance for #10 wire at 16 amps and 48V (or would
you use 60V for the wire distance calculation?
Thanks for your replies

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Solarline parallel connectors

    If I'm reading you right, and I may not be, this is a no-no. Any more than two panels or strings in parallel and you need to have circuit protection for each one. You shouldn't parallel two panels or strings and consider it "one" then feed it to the combiner box where it will tie to another similar set-up.

    And if I'm not understanding the question right, someone will be along any minute now to correct me. :D
  • bethbeth Solar Expert Posts: 32
    Re: Solarline parallel connectors

    From what I have read seems like you can have 2 strings in parallel with out fuses? Wondering what the logic is behind your answer?

    And I am also still wondering what these are connectors are designed for?

    Can any body else chime in on this, Thanks!
  • BB.BB. Super Moderators, Administrators Posts: 30,485 admin
    Re: Solarline parallel connectors

    Say you place two solar panels in parallel (+ to +; - to -)... And then picked a place to short circuit anywhere in the electrical path...

    In no place will the wiring/solar panels carry more than 1x the Isc current to the short circuit. At the point of the short, you will have 2x current (power from each side of the wire coming to the short)--but that is it.

    Now place three (or more) panels in parallel... And short any single point... Now the current in some of the wires will be 2x (or more if >3 panels in series)... This exceeds the design rating for the wiring and solar panels. It would then be possible for the wiring (or solar panel) to overheat and light the insulation or nearby flammable materials on fire.

    That is why a series fuse/breaker is required when three or more panels (or panel strings) are connected in parallel.

    Remember, Power=I^2 * R -- So if you double I (current), you actually can get 4x the amount of heat... This means that current ratings and protection (using fuses, breakers, etc.) is a very important part of reducing fire hazards in the event of a short circuit.

    Other important features include the use of tempered glass (instead of plastic) for the panels, and the use of flame rated plastics in the construction of the panels and their wiring. Note that most plastics, even those flame rated by UL/NRTL will still burn quite nicely in the right conditions (enough heat and oxygen).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bethbeth Solar Expert Posts: 32
    Re: Solarline parallel connectors

    Thanks for that explanation Bill so I guess that means that my original scenario is no good , so then are these connectors only used for 2 panels in parallel.
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