What's the difference between using breakers or fuses in a combiner box?

showmeshowme Registered Users Posts: 63 ✭✭
in Solar Beginners Corner #1
Getting ready to order my combiner boxes, and it seems there's a choice between fuses and breakers. Why? And which one should be used?

"Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


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  • PhotowhitPhotowhit Solar Expert Posts: 5,827 ✭✭✭✭✭
    #2
    Breakers can be used as switches, This can be valuable when trouble shooting. I only used breakers because the cost was minimal. I had a fuse box which I could convert and had the distribution blocks, fuse blocks, even a few fuses. I think I bought a box of fuses for $20 off eBay....

    Oddly I actually picked up an Outback dual array breaker box unused later for $100 but never felt I needed to swap it out as it was setup and working fine. I also had a DC clamp meter which solves a lot of the things the breakers would help with.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • mike95490mike95490 Solar Expert Posts: 9,582 ✭✭✭✭✭
    #3
    Breakers.
     Most DC fuse holders, are rated touch safe, which only means you are unlikely to get shocked.   The fuse cannot be removed from a live circuit to check it, or you will arc weld the fuse holder.  Breakers can be obtained that are rated for Switch duty and you can compare string A to B to C for a very quick operation check, that you cannot do with fuses.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • showmeshowme Registered Users Posts: 63 ✭✭
    #4
    Thanks, guys! I intended to get Midnite Solar's 15a, 150vdc as someone suggested, but kept coming across the fuses in some. I'd rather flip a switch than pull and replace fuses anytime. I remember the old fuse box at my grandparents and in-laws houses. Seems we never could find the right fuse or a non-burnt fuse when we needed one. Thanks again. I just keep finding things I didn't know I didn't know.

    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


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  • PhotowhitPhotowhit Solar Expert Posts: 5,827 ✭✭✭✭✭
    edited December 2021 #5
    Using a fuse in a combiner box, isn't a huge thing as Mike makes it out. You will want to have the array line on a breaker at th power center.
    Then you can flip the breaker and pull a fuse. Of course if the fuse is on your roof...

    In the end a DC clamp meter makes most of those situation go away. I'd rather not flip a breaker under load, particularly a DC breaker. I think Bill has already posted a photo about the differences in DC vs AC current, and the ability of DC to maintain an arc.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • FingersFingers Registered Users Posts: 19 ✭✭
    #6
    I lived with an old 1960's Bakelite fuse box with ceramic fuses in my home for over 20 years, and it only popped a fuse only once.
    When I changed it to a modern consumer unit (breakers), it really showed up the problems that were there all the time. A 3 kilowatt electric kettle and a dishwasher burning out the cables in the wall. Damp wall sockets in a bedroom, shorting out. The breakers tripped out until the jobs got done.

    Yes that was normal mains electricity (not solar), but it really shows how modern breakers can do their job well.
    However, looking on Youtube at solar breakers and fuses was a real shocker! Fake breakers, just a bit of wire inside the breaker.
    Looking at some videos, even manufacturers of good breakers don't seem to get the whole job done, and are subject to high resistance. 

    I'd like to know if anyone has used both fuse and breaker on the same circuit? And what about the resistance?

    Showme, what ever you choose to go with make sure it's a good well known manufacture, and research it well on youtube and the net. Every day is a school day.
             
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  • showmeshowme Registered Users Posts: 63 ✭✭
    #7
    Thanks for all the good information (and warnings) on this, folks. You're right, Fingers- every day is school day, and I'll keep studying till I get it right.

    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


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  • mike95490mike95490 Solar Expert Posts: 9,582 ✭✭✭✭✭
    #8
    I only use the breakers sold by Midnight ( distributed via our host Wind-Sun )

    Many types, Bolt & DIN rail, AC, DC, HVDC and tested - made by a major CB mfg, not fake stuff.
    " MidNite breakers have been evaluated by ETL to 150VDC and are listed for US and Canada. All of the NRTL listings still apply."
    " MidNite's breakers are rated to break the full rated load at the rated voltage repeatedly, with NO DAMAGE. Always use a properly sized breaker for disconnecting. "

    all:  https://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=16&productCatName=Breakers

    Bolt  ( DCVDC )
    https://www.midnitesolar.com/productPhoto.php?product_ID=197&productCatName=Breakers&productCat_ID=16&sortOrder=13&act=p

    DIN  ( 150VDC )
    https://www.midnitesolar.com/productPhoto.php?product_ID=183&productCatName=Breakers&productCat_ID=16&sortOrder=18&act=p






    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

    · Share on Twitter
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