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Siemens QO breakers DC rating?

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  • Mike90250
    replied
    Breakers make a handy switch for when you need to reboot the charge controller, but in real world, your 8A panels can't trip a 10A breaker, except for a Edge of Cloud lensing event.

    Leave a comment:


  • PNW_Steve
    replied
    Originally posted by Sunking View Post
    Dead serious, I am a professional electrical engineer with 40 years of experience. A solar panel is a Current Source, not a voltage source. With one or two strings of panels, makes it impossible for a solar panel system to operate a fuse. A 250 watt panel with a dead bolt fault will only deliver roughly 8 to 10-amps of current. 8 to 10 amps of current on a 15 or 20 amps breaker or fuse is a normal load current and will never operate a fuse.That is why electrical codes do not require a fuse on solar panels unless you cross the line with 3 or more strings.

    Look at any panel specification and look for the spec Isc and learn what it means. Isc = Current Short Circuit. A 200 watt panel Isc = roughly 8 to 10 amps. That is the absolute maximum current that panel can deliver with its output shorted out (two output wires twisted together tightly.) Please explain how 8 to 10 amps is going to operate a 15 or 20 amp fuse or breaker.

    You can certainly use OCPD on the panels if you wish, but they are not required and an unnecessary expense.
    In my own situation I have 4 strings that run about 8.5A max so I used 10A breakers.

    Last edited by PNW_Steve; 11-12-2020, 11:58 PM.

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  • Sunking
    replied
    Originally posted by PNW_Steve View Post
    Apparently there are few to none when it comes "right designs". We use overcurrent protection on every circuit.
    Dead serious, I am a professional electrical engineer with 40 years of experience. A solar panel is a Current Source, not a voltage source. With one or two strings of panels, makes it impossible for a solar panel system to operate a fuse. A 250 watt panel with a dead bolt fault will only deliver roughly 8 to 10-amps of current. 8 to 10 amps of current on a 15 or 20 amps breaker or fuse is a normal load current and will never operate a fuse.That is why electrical codes do not require a fuse on solar panels unless you cross the line with 3 or more strings.

    Look at any panel specification and look for the spec Isc and learn what it means. Isc = Current Short Circuit. A 200 watt panel Isc = roughly 8 to 10 amps. That is the absolute maximum current that panel can deliver with its output shorted out (two output wires twisted together tightly.) Please explain how 8 to 10 amps is going to operate a 15 or 20 amp fuse or breaker.

    You can certainly use OCPD on the panels if you wish, but they are not required and an unnecessary expense.
    Last edited by Sunking; 10-13-2020, 11:56 AM.

    Leave a comment:


  • PNW_Steve
    replied
    Originally posted by Sunking View Post
    Why do you think you need breakers? You do know with the right design, no breakers or fuses are needed. Guess you want to spend the cash huh?
    I can't tell if you are joking or serious........

    Apparently there are few to none when it comes "right designs". We use overcurrent protection on every circuit.

    Leave a comment:


  • Mike90250
    replied
    Breakers are handy as a switch, for combiners to compare string performance as a quick sanity check. Also useful as a switch to disconnect PV from charge controller

    Most fuse/holder combos are NOT rated for circuit interruption (meaning the contacts will fry if you pull a fuse while circuit is live) (only for the fuse to blow and interrupt)

    And it's good practice to protect the cable from the battery to charge controller, in the odd chance the controller fails.

    While sizing strings and only using 2 parallel PV strings, protection is not required, it's handy

    Leave a comment:


  • Sunking
    replied
    Why do you think you need breakers? You do know with the right design, no breakers or fuses are needed. Guess you want to spend the cash huh?

    Leave a comment:


  • PNW_Steve
    replied
    My apologies, I somehow turned "Schneider" into "Siemens"

    The breakers that I am looking for are actually Schneider.

    Stuck on stupid......

    Leave a comment:


  • PVAndy
    replied
    Originally posted by PNW_Steve View Post

    Doesn't look like they have them.

    Thanks for trying.
    I'm surprised/, Did you try calling them? I've bought them there many times

    You an also try https://www.solar-electric.com/marin...akers.html?p=2

    Andy

    Leave a comment:


  • PNW_Steve
    replied
    Doesn't look like they have them.

    Thanks for trying.

    Leave a comment:


  • PVAndy
    replied
    Originally posted by PNW_Steve View Post

    Thanks.

    Any clue where I can find the breakers I am looking for?
    https://www.altestore.com/energy/midnite%20solar

    Leave a comment:


  • Mike90250
    replied
    I don't know about the Siemens-QO


    CARLING breakers rated for 150VDC

    http://www.midnitesolar.com/pdfs/CA1...-767-321-L.pdf

    Carling may make a Load Center version , these are bolt on.

    The C-Series hydraulic/magnetic circuit breakers are
    ideal for applications that require higher amperage and
    voltage handling capability in a smaller package. They are
    available in 1-6 poles, 0.02-100amps, UL Recognized up to
    480VAC or 150VDC, UL489 Listed up to 240VAC or 125VDC,
    with choice of time delays, terminal options, actuator
    styles and colors.
    Carling Technologies, Inc.
    60 Johnson Avenue • Plainville, CT 06062-1177
    Phone: (860) 793-9281 • Fax: (860) 793-9231
    Email: sales@carlingtech.comwww.carlingtech.com

    Leave a comment:


  • PNW_Steve
    replied
    Originally posted by Mike90250 View Post
    here - the 150VDC rated from Midnight, not sure who makes them.
    http://www.midnitesolar.com/productP...Order=13&act=p
    Thanks.

    Any clue where I can find the breakers I am looking for?

    Leave a comment:


  • Mike90250
    replied
    here - the 150VDC rated from Midnight, not sure who makes them.
    http://www.midnitesolar.com/productP...Order=13&act=p

    Leave a comment:


  • PNW_Steve
    replied
    Originally posted by bob-n View Post
    I thought that QO was the Schneider SquareD breaker tradename. SquareD QO are only rated for 48VDC.
    https://www.se.com/us/en/product-ran...egory-id=50310

    The important thing to remember is that interrupting DC is much more demanding than interrupting AC. That's why these 240V AC breakers are only rated for 48V DC.

    The Midnight Solar breakers are rated for 150VDC. Sounds like you need them.
    According to the Schneider website they make breakers rated for both 48v and 125v. I have not had luck so far finding the 125v rated breakers. The 48v won't work for me as my Voc is going to be around 80v.

    Leave a comment:


  • bob-n
    replied
    I thought that QO was the Schneider SquareD breaker tradename. SquareD QO are only rated for 48VDC.
    https://www.se.com/us/en/product-ran...egory-id=50310

    The important thing to remember is that interrupting DC is much more demanding than interrupting AC. That's why these 240V AC breakers are only rated for 48V DC.

    The Midnight Solar breakers are rated for 150VDC. Sounds like you need them.

    Leave a comment:

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