Fuse or circuit breaker

ozarkgem
ozarkgem Registered Users Posts: 21 ✭
in Off Grid Solar & Battery Systems #1
I am installing my Magnum 4024 and it calls for a 175 amp fuse between the battery and inverter. What are you using and what brand? For now
my battery is setting under a porch within 5 feet of the inverter. I would also like a disconnect switch between the battery and inverter. I have
some 250 amp and 400 amp AC switches but I don't know if they would work or not. What would you use. I want it done right. Can't afford a fire.
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  • unicornio
    unicornio Solar Expert Posts: 217 ✭✭
    #2
    Re: Fuse or circuit breaker

    perhaps the cheapest in your case is that you put a good fuse rated for DC and for convenience to install one of these to your existing for AC ... over time you can jump to check its value and if they can be useful ...but you can use it for maintenance and inspections by turning on/off comfortably

    fuses (these large fuses) are only cheap if not merge often, but certainly do its function safely and accurately ... and usually lose less than any other protective device ...

    anyway I do not find too expensive a good precision magnetic/thermal/hydraulic breaker, rated for use in DC, to safely protect both, inverter and batteries...
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #3
    Re: Fuse or circuit breaker

    I think they call for a " Class T Fuse " this not your ordinary fuse, it has a special load disconnect. if your in doubt, call Magnum. there could also be a code issue.

    Class T fuses. These non-renewable fuses are current-limiting and are designed for protection of feeders and branch circuits in accordance with the NEC. Current ratings range from 0A to 1200A for 300V rated fuses, and 0A to 1,200A for 600VAC rated fuses. Class T fuses are available with DC ratings. The interrupting rating is 200kA rms symmetrical.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: Fuse or circuit breaker

    DC switches are usually larger/heavier duty than the equivalent AC version.

    DC current sustains arcs very nicely and need the specially designed switches for reliability.

    If you don't plan on switching the AC switches often under heavy load--Then they probably will work OK. Hopefully, worse case, the switches arc excessively under switched load and fail over time. Then you replace with another switch.

    There are DC Battery switches which can be handy. I have never used one--But I would suspect that they are not really great to switch under load either (i.e., not spring loaded with fast snap action).

    If you go with a switch and fuse--These Blue Sea fuse holders look really nice as they can bolt directly to a battery or bus bar (one and two fuse holders available).

    Attachment not found.Attachment not found.

    And you can get a DC 175 Amp breaker for ~$80.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #5
    Re: Fuse or circuit breaker

    If you want a fuse, you want a class T fuse as Blackcherry mentioned. It is not safe to pull one of these fuses under load, so it is common to install them with a disconnect switch. Open the disconnect before you install or remove a fuse. A DC rated disconnect switch is expensive, Have you considered DC circuit breaker? You get overcurrent protection and a disconnect all in one.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #6
    Re: Fuse or circuit breaker

    Sorry I haven't called, that E-Panel, in my PM, is a real bargain at $211 about $250 shipped, it also has a shunt for a battery monitor and fusing for your AC out put and is designed to mount the inverter on the front panel. It also has spaces for breakers where your solar panels come into the Charge controller and you can mount most charge controllers to the side. I believe that inverter calls for a 250amp fuse or breaker, as that is what this E-Panel has and it's made for that invereter. This also includes the shroud and top plate to make your inverter code compliant, code doesn't allow for exposed DC wires, we don't have anyone looking over our shoulders in most of Missouri... yet!

    I'll PM you the link again. This is a real bargain and your a bargain hunter...

    You may have the 4024 PAE(?) which has 120/240 output? though I can't imagine that would change the breaker between the battery and inverter the out put breakers would be a different configuration....
    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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  • ozarkgem
    ozarkgem Registered Users Posts: 21 ✭
    #7
    Re: Fuse or circuit breaker

    I wasn't going to use the AC switch under load. I just wanted a switch between the battery and inverter. I hate sparks when I hook things up. I would turn the inverter off
    before I used the switch. Maybe a few times a year.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #8
    Re: Fuse or circuit breaker

    Hi ozark..

    Using a Circuit Breaker is the traditional solution for protecting the Inverter cables plus a disconnect switch.

    As has been noted previously on this site, the correct Class T fuse, and holder is not inexpensive, and should one pop, not cheap to replace. Furthermore, almost all high quality inverters have a large capacitor bank on the battery leads (this may have been the sparking that you were referring to). The large inrush current when a switch is thrown to 'ON', there is a large spark, which could perhaps weld contacts of an AC rated switch. At least this sparking could be harm the contacts after some use. YMMV. Bottom line, a MidNite DC-rated breaker is a real deal, as linked at the bottom of BB's post is the traditional approach. Good Luck, 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.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #9
    Re: Fuse or circuit breaker

    You might check your manual, from what I have It appears they want a 250 Amp Breaker, or 300 Amp fuse.

    Link to Magnum MS Inverters.
    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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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #10
    Re: Fuse or circuit breaker
    ozarkgem wrote: »
    I am installing my Magnum 4024 and it calls for a 175 amp fuse between the battery and inverter. What are you using and what brand? For now
    my battery is setting under a porch within 5 feet of the inverter. I would also like a disconnect switch between the battery and inverter. I have
    some 250 amp and 400 amp AC switches but I don't know if they would work or not. What would you use. I want it done right. Can't afford a fire.

    A 4024 takes a bigger fuse or breaker than 175 amp. That's full load amps, but doesn't account for surge. A 4024 more typically has a 250 amp breaker on it. That inverter will pull 266 amps at full surge power for 5 seconds.

    AC switches and breakers, used for DC applications, are usually not even legal because they don't meet code as they aren't DC rated. You can buy the appropriate circuit breaker for your inverter from either Magnum Energy or MidNite Solar.
    --
    Chris
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