code for array combiner to cc: disconnect or breaker?

jtdiesel65
jtdiesel65 Solar Expert Posts: 242 ✭✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
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.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    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).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #3
    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 ||
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  • jtdiesel65
    jtdiesel65 Solar Expert Posts: 242 ✭✭✭
    #4
    thanks.
    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.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #5
    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.  
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  • jtdiesel65
    jtdiesel65 Solar Expert Posts: 242 ✭✭✭
    #6
    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.
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