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What breaker size do I need for the battery bank between and inverter. MPP LV 5048 I think the battery cable size is 1/0.

lllaible

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What breaker size do I need for the battery bank between and inverter. MPP LV 5048 I think the battery cable size is 1/0. I'm starting out small with 4 100 amp solar panels and 4 200 amp sealed lead acid batteries.
 
i am an electrician and not a solar expert. breakers and fuses are to keep the equipment and WIRE from overcurrent. size the fuse or
breaker for the 1/0 wire and you will keep it from overcurrent. you could go lower if you wanted to protect other devices down the line.
if you understand what i mean you can fuse it for the max rated cont. output of the inverter and it should be far less than the max wire rating.
 
Watts ÷ volts x 1.2 = fuse size in amps required as a general rule. I found this on the internet so 5000 watt ÷ 48v x 1.2 should give me 125 amp breaker is this correct? The 1/0 wire will be 5ft or a little.
 
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5000 ac watts / .85 conversion efficiency / 48 volts = ~122 dc amps
~122 dc amps * 1.25 fuse headroom = ~153 fuse amps
You want a quality 150 amp fuse or breaker minimum
With pure copper 1/0 awg wire with insulation rated to 105 celcius the upper limit for the fuse is ~285 amps.
 
Thank you Smooth. I'm new at this and I'm clueless so a quality breaker min 150 amp-285 amps is this correct?
 
Thank you Smooth. I'm new at this and I'm clueless so a quality breaker min 150 amp-285 amps is this correct?
Yes
The 285 amps is dependent of the wire spec I defined above.
Personally I would not go that high.
I don't wan't my wires getting that hot even if they are rated for it.
 
I think I will order a 200 amp breaker that is in the middle of what you stated. Thanks for answering my question and have a great day.
 
Does anyone make a quality 200A DC breaker? I can't seem to find anything other than the Bussman automotive breakers... And It looks like Midnite doesnt make a 200A breaker...
 
Thanks for the reply. I now realize that Bussman doesnt even make a 200A version, but Tocas does offer a 200A breaker (which you mentioned) which is the only option that I know of. Unfortunately the Tocas 200A breaker is not marked or approved with any certifications. MIdnite does offer a 250A and 175A breaker for about $90, but not a 200A, which is weird. Im thinking going with the Midnite 175A and my 200A fuse, rather than the Tocas 200A breaker, 200A fuse, and disconnect switch. This will only be about $30 more but will be easier and a cleaner setup. And I believe the midnite breaker is also available with a disconnect relay that could link up to an inverter or BMS.
 
Do not forget the quality part
And possibly more important, don't forget the 105C part.

If 90 degree C rated wire, it's good for 260A as single conductors in free air or 170A as part of a cable. In either case, assuming 30C ambient.
It's OK to round up to 175A.
 
Thanks for the reply. I now realize that Bussman doesnt even make a 200A version, but Tocas does offer a 200A breaker (which you mentioned) which is the only option that I know of. Unfortunately the Tocas 200A breaker is not marked or approved with any certifications. MIdnite does offer a 250A and 175A breaker for about $90, but not a 200A, which is weird. Im thinking going with the Midnite 175A and my 200A fuse, rather than the Tocas 200A breaker, 200A fuse, and disconnect switch. This will only be about $30 more but will be easier and a cleaner setup. And I believe the midnite breaker is also available with a disconnect relay that could link up to an inverter or BMS.

I like what I see in the specs for the Midnight breaker.
50kA interrupting.
Not polarized.

Checking out the specs for it:


I see it is "medium" trip speed, and at 1000% of rating (1750A) trip time is 0.008 to 0.10 seconds.

I would want to select a fuse slower than that for such currents (or maybe currents in the 500A to 1000A range), but faster than the breaker for extreme overloads. Idea being, don't blow the fuse for something the breaker can handle, but have fuse save breaker from being single-use protection in case of a dead short.

Class T JLLN 200A fuse:


Shows 0.015 seconds at 1000A. Much faster than the breaker 0.3 to 2.0 seconds for 500% of rating.

But a 350A fuse lasts 2.5 seconds at 1000A. At 2000A and above, it clears in 0.01 seconds or less. Might protect breaker which is never shown faster than 0.008 seconds.

Per NEC, 1/0 would have been acceptable as ground wire for up to 800A over-current protection. So I figure it has no problem clearing a 350A fuse in case of a short. It is still protected against overload by the 175A breaker.

 
Might protect breaker which is never shown faster than 0.008 seconds.

That is a suspicious amount of time, one half cycle of 60 Hz.
As if it is the arc interruption time in an AC application. But this is supposed to be for DC.
I wonder how well it was tested and measured with DC. Ratings are for both AC and DC.
 
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