code for array combiner to cc: disconnect or breaker?

I was wondering if a non-fused disconnect is enough. But does code require a fuse/breaker? If each string in the array has a breaker, I'm not sure why one would need a breaker/fuse for the entire array given the wire size is rated for the amperage.


  • BB.
    BB. Super Moderators, Administrators Posts: 33,490 admin
    You don't need another breaker unless the single run rating is less than Isc-array rated current.

    Having (for example) a combiner box at the array, and a single switch (rated for VDC/Current) or even a rated breaker next to the MPPT charge controller can make servicing a bit easier (local array on/off switch).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    I have my combiner breakers outside, on the pole, where the arrays are.   I also have a handy breaker inside. When updating firmware or changing the setpoints, often the controller has to be disconnected from the array and then cold boot from the battery.  Breakers are only $20, but they sure make things easier.  
    Fuses are a bit less expensive but their contacts  are not rated to "open" a live circuit
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    gen: ,

  • jtdiesel65
    jtdiesel65 Solar Expert Posts: 242 ✭✭✭
    I have combiners with breakers on the arrays. I currently have din mount breakers inline in a midnite panel and next to the charge controllers. But I am rewiring the PV side with some conduit and was thinking about ditching the panel and breakers for a couple disconnects.  I'm not a fan of din mount breakers.  I already have a couple spare panel mount breakers that would be fine, so I ended up buying an enclosure. I'll put the panel mount breakers in the enclosure (I'll need to cut knockouts for them) and replace the midnite panel.
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Just make sure the panel mounted breakers are rated fo DC, as AC breakers are not suitable, with a few exceptions, which are rated for both.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • jtdiesel65
    jtdiesel65 Solar Expert Posts: 242 ✭✭✭
    Thanks. They are the DC ones that were cc->battery. I rewired that side of the CC and replaced those breakers with new DC breakers in the Schneider PDP.  Originally I had cc->battery breakers in one panel and pv->cc breakers in another. Legacy wiring from long ago.