Breaker direction?

garynappi
garynappi Registered Users Posts: 120 ✭✭
edited January 2021 in Solar Beginners Corner #1
Funny I looked for an answer but did not find anything concrete.

Do DC solar breakers have "IN" and "OUT" lug requirements? Can the "In" be on the "top" and out be on the bottom?
I've looked at a number of combiners and it seems as if there's no real "wrong" way to connect breakers. Below is a combiner pic from Ebay.


· Share on Twitter

Comments

  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    edited January 2021 #2
    High voltage DC breakers often have an arc suppression guard that helps to reduce time of a breaker opening DC arc.  The hot arc rises up so DC breakers have an orientation so the arc suppressor engages from the optimum direction.
    · Share on Twitter
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #3
    DC breakers with markings for positive need to have the conductor with the highest energy  potential connected to that terminal. Using a simple battery with a DC load circuit it's logical that the battery would be the source of highest energy potential because it's the only source,  however it becomes confusing to some when other components are added, such as charge controllers and solar arrays.

    Although logic may suggest that the charge controller is the source of the energy, therefore it should be connected to the positive terminal, it is actually the opposite, the battery has the highest potential energy, capable of delivering hundreds or if not thousands of amps in the case of a short circuit. Since the sole purpose of over current protection (OCP) is to protect the conductors downstream having an OCP  device, fuse or breaker, should be as close to the battery terminals as possible, as a short circuit before the protection device renders it useless.

    When a charge controller is connected to a battery the lower capacity OCP protecting the charging source conductors which are likely smaller, should also be placed as close to the battery as possible (the battery  having the highest potential energy) although I'm sure most do not do so by assuming the controller is the source.

    Solar arrays theroitically are further isolated from the battery by the controller, but are they?  Should breakers, if used, be polarized towards the side of highest potential?. 

    This naritive potentially provides  more questions than answers, but in short, polarized circuit breakers rely on arc quenching to preserve the contacts from burning, perhaps even if switched under load, there are circuit breakers which are not polarity sensitive which may be the better choice to circumnavigate the ambiguity in part. Thoughts.

    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.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,609 admin
    #4
    For a solar array, the pals themselves are the source of current (a bunch of panels in parallel feed a shorted panel/harnes--Typically 3 or more panel strings in parallel).

    The reason for polarity is that the DC breakers use a magnet to "blow" the arc into the quenching channel. If the current is flowing in the "wrong" directly, the arc is pulled into the guts of the breaker and can cause the arc to be sustained and melt/start a fire inside the breaker (as I understand/remember).

    There is a newer requirement that DC breakers should not be polarity sensitive--So you can find them for sale if you need a non-polarity sensitive breaker.

    An example of non-polarized DC breakers (I don't know anything about the vendor--But these are 500 VDC rated breakers--Pretty impressive):

    https://www.amazon.com/LANGIR-Photovoltaic-Polarized-Circuit-Certificates/dp/B012MWNT06?th=1

    And Midnite as a mix of polarized and non-polarized breakers:

    http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=16&productCatName=BREAKERS

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #5
    For the MidNite breakers,  there is now a very descriptive Poster for their entire circuit breaker lineup:
    breakers_11x17.jpg (1056×1632) (midnitesolar.com)

    FWIW,  Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
    · Share on Twitter
  • garynappi
    garynappi Registered Users Posts: 120 ✭✭
    #6
    Thanks all. I ordered a Langir breaker.
    · Share on Twitter
  • garynappi
    garynappi Registered Users Posts: 120 ✭✭
    #7
    Another related question, I also read elsewhere that DC breakers cannot be oriented upside down?
    · Share on Twitter
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    edited January 2021 #8
    Not all DC breakers have a magnet arc director.  If they do they should have polarity markings on or near terminals  It may be labelled 'Line' for positve side and 'Load' for negative side. . I believe all the CBI-Electric breakers that Midnight sources do have magnets..  I have not seen a DC breaker without arc suppressor guard which with proper breaker orientation should be above the contacts to break up the arc.

    Having a magnet arc director can help compensate for not having the breaker in proper orientation but it is preferred to mount breaker in normal front text reading orientation.  Upside down is least desireable.

    A DC breaker, based on its voltage and amperage rating, should have enough separation of contacts in open position to break arc regardless of magnet or suppressor guard assist.  The longer the time the arc last, the more it damages the contacts surface so the arc extinguishing enhancements are primarily for reliability of breaker.

    Not all DC breakers are built the same way so read any instructions that came with your particular breaker. 
    · Share on Twitter
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #9
    Some reading material that may be of interest, see attached pdf 
    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.
    · Share on Twitter

Categories