need advise for 24v 300A breakers
- Thread starter gpower07
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John Frum
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My mistake, I thought we were talking about ampacity.
Also the OP mentions that his system is 24 volts.
Also I don't think anyone mentioned the round trip circuit length.
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
The chart below that goes to 150A for a 10% voltage drop, but I really don't like to allow a voltage drop that large between two critical components like the Battery and Inverter.
So I guess the net result is that from an ampacity point of view, 4AWG is OK. From a voltage drop point of view, it would be best to have a larger wire.
In either case, If you have a 200A fuse, 4AWG is too small.
So I guess the net result is that from an ampacity point of view, 4AWG is OK. From a voltage drop point of view, it would be best to have a larger wire.
In either case, If you have a 200A fuse, 4AWG is too small.
SolarQueen
Making renewable do-able at www.alteStore.com
SolarQueen
Making renewable do-able at www.alteStore.com
As for what the OP needs, from what I understand, they have a 24V 2000W inverter. If so, to find out what size over current protection they need (breaker or fuse) divide the watts by the lowest working voltage time 1.25. So, 2000W / 21V x 1.25 = 120A breaker needed. That's a far cry from 300A. (Although I question this, because they also said max current from system is 120A, so did they already do this math, or are they actually seeing that, in which case, the system probably isn't 24V but 12V?)
CascadeOffGrid
Off Grid Design and Installer
What is the surge rating on the inverter? Fuse and wire size should account for the surge rating. Usually the inverter manufacturer has a recommended time delay fuse size. I would suspect that a 2000W inverter will be able to surge to 3000W. Usually a 2000W inverter at 24V will be best paired with a 200A fuse and then appropriate wire to match. Undersizing wire to an inverter will give you all kinds of trouble if you are trying to operate the inverter at high capacity or if you are trying to start big loads.
John Frum
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Unless an inverter's surge capacity duration is long enough to flirt with OCPD's trip curve then its not really a factor.
CascadeOffGrid
Off Grid Design and Installer
Agreed as long as the correct type of OCPD is being used.
Good luck finding a fuse that carries it’s rating out 9 places past the decimal ?
Aussie Solar
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Hi Gpower07,
I'm new here
. Ok first of to answer your question, without knowing anything about your system really. You want a fuse switch disconnect which holds NH fuses. Quality brands like Bussman and Woehner make them. They get pretty pricey for the Size 2 3 pole options which is what you'll need for 300a. If you need 160a its quite a bit cheaper. You want slow blow fuses.
link so you know what I'm talking about:
Online catalogue
pim.woehner.de
How long and what size did you say your dc cables are? I read something about a 10% voltage drop and 4AWG. You don't want either of those. Having an unbalanced system design like that is going to create DC ripple, the voltage drop an increase in current which will make it worse. Sort out you cable size and length.
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
Like @Aussie Solar said, when you get to higher amp DC breakers, it gets *very* pricey to get one that is going to do the job. The breakers on amazon the are specified for over 150A are all cr@p that should not be trusted. (it sounds like you have discovered this first hand... consider the cost of the breaker tuition.)
I used to have the opinion that everything should be done with breakers. That way I could always reset a breaker an get on with it. However, I have done a complete 180 on this when it comes to high amp DC breakers. My current feeling is that when you are talking about over-current protect at levels of 100A -150A or above, you should be talking about only blowing in extreme catastrophic events. If your design might regularly trip that size breaker.... you have a bad design. I now just use a fuse for the larger current protection and call it good. It is cheap and reliable and unless something really bad happens, you will never have to touch it after it is installed. ( In one design for a boat where getting a fuse could be a problem, I specified using a 2nd, unwired fuse holder to hold a spare. Even then, if the fuse blows, you likely have bigger problems than finding a spare fuse.)
I used to have the opinion that everything should be done with breakers. That way I could always reset a breaker an get on with it. However, I have done a complete 180 on this when it comes to high amp DC breakers. My current feeling is that when you are talking about over-current protect at levels of 100A -150A or above, you should be talking about only blowing in extreme catastrophic events. If your design might regularly trip that size breaker.... you have a bad design. I now just use a fuse for the larger current protection and call it good. It is cheap and reliable and unless something really bad happens, you will never have to touch it after it is installed. ( In one design for a boat where getting a fuse could be a problem, I specified using a 2nd, unwired fuse holder to hold a spare. Even then, if the fuse blows, you likely have bigger problems than finding a spare fuse.)
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chrisski
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I noticed not all ANL fuses are rated the same way, kind of like the breakers I guess.
I noticed the cheaper priced ANL fuses were audio, and none of the listed the "6,000 Ampere Interrupt Rating satisfies ABYC requirements for main DC circuit protection on large battery banks" that Blue Sea does. I had already got the Blue Sea ANL Fuse box, but bought an audio ANL fuse for it. I now have two Blue Sea ANL fuses on order.
I really don't know why the difference is there for audio circuit breakers and main DC circuit protection for large battery banks, but I've spent so much on my system, I don't want to lose it because I wanted to save $20 on a fuse.
I noticed the cheaper priced ANL fuses were audio, and none of the listed the "6,000 Ampere Interrupt Rating satisfies ABYC requirements for main DC circuit protection on large battery banks" that Blue Sea does. I had already got the Blue Sea ANL Fuse box, but bought an audio ANL fuse for it. I now have two Blue Sea ANL fuses on order.
I really don't know why the difference is there for audio circuit breakers and main DC circuit protection for large battery banks, but I've spent so much on my system, I don't want to lose it because I wanted to save $20 on a fuse.
MadElectrician
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Took a minute to figure out what you were trying to do. You don't want to send low voltage DC very far as massive wire is required. If your inverter is located right next to your batteries, ground fault fusing (short circuit) isn't required, and your inverter should protect against over current (I would think). Proper wire / breaker sizing is actually pretty complicated and requires knowing how to use the NEC tables. It involves amps, wire type, distance, terminal connection temp ratings, ambient temperature, type of load (continuous v non-continuous) motor loads are another thing entirely. Then the are demand considerations such as what appliances will be used at the same time. While I would be happy to help with this, my recommendation would be to wire your invertor straight to a small residential panel with a main breaker right around the peak amps your invertor can supply. Then, use standard circuitry from there. 14awg wire for a 15A circuit with each receptacle presumed to be 1,800W (stick with around 10 or less). 12awg wire for a 20A circuit for something like a heater or small - medium AC unit. Getting into bigger stuff, 10awg for a 30A 2 phase appliance like a range or heater. Rule of thumb - your wire must be rated at 125% of your breaker rating. If your breakers are 90C rated, and you use THHN wire, you can use the 90C column in the NEC table - otherwise use the 75C column. Hope that helps.
Here is a circuit breaker rated for 32V at 300A. It is rated for marine use so I expect this is real (never used one so I can't vouch for its quality). It is not going to serve as a switch, but neither does a fuse. The pic is the generic version, the part linked is rated for 300A. Note this is automatic reset breaker which may not be what you want.
www.delcity.net
Del City - Item #: 77100
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I can't speak to the quality of this breaker, but it has a manual reset and is also rated for 300A
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
I would not recommend using this breaker for a couple of reasons.Here is a circuit breaker rated for 32V at 300A. It is rated for marine use so I expect this is real (never used one so I can't vouch for its quality). It is not going to serve as a switch, but neither does a fuse. The pic is the generic version, the part linked is rated for 300A. Note this is automatic reset breaker which may not be what you want.
View attachment 26148
Del City - Item #: 77100
1) Auto reset of a 300A breaker is almost certainly not appropriate for anything in DIY solar. If you have an event that causes a 300A breaker to trip.... something really bad happened. I would not want it to automatically turn back on without knowing what the event was and insuring it is fixed.
2) This style of breaker is notorious for being highly unreliable. The quality breaker manufactures don't build these larger that 150-200A. I did some research on it and concluded that you just can't get enough copper and mechanism into this size package and still have a reliable breaker.
If you look at the reviews a number of folks say it trips at 120 amps amongst other problems.
As indicated in the rest of the thread this is just not beefy enough to do what it says.
I would never use that and have learned to never use off brands for something this important.
The only reputable (to me) companies I have personally encountered selling (to consumers) breakers above 200A are:
Xantrex (250A 160V)
Midnite (250A 125V)
Outback (250A, 125V)
All seem to be panel mount breakers and in the ballpark of $100
Xantrex (250A 160V)
Midnite (250A 125V)
Outback (250A, 125V)
All seem to be panel mount breakers and in the ballpark of $100
