Breaker size and wire for inverter

[Austin68]

So i am setting up a small system for a shed so that i can power a few things. What im unsure of is what size of breaker and wire to run from the batteries to the inverter. Currently I have two 12v in series and will be using a 24v 3000w inverter. This highest load I anticipate running is 15a off the inverter. I have seen some places say that 8awg will work and I have see some others say to run 1/0.

 

[Hedges]

3000W/24V=125A
Might as well size wire for inverter's capability, rather than just 1800W anticipated load.
8 awg would supply that load, but at least 2 awg would be better in case you want to power something larger.
All assuming short wires; if long run to battery then larger gauge is needed.
If you can fit 2/0, so much the better.

 

[Austin68]

What about breaker size?

 

[Hedges]

Breakers and fuses should be 1.25x maximum continuous current, to avoid nuisance trips. But no larger than wire ampacity.
You can find charts of NEC or others for ampacity of wires with various temperature rating insulation. A chart for single wire in free air (typical for battery cables) will allow higher current.

Lithium or lead-acid?

The other rather of a fuse or breaker is AIC, capability to interrupt short-circuit current. The rating can range from 3000A to 20,000A.
I've read of a 100 Ah AGM battery being able to put out 4000A. The internal resistance values I've seen for LiFePO4 suggest as high as 20,000A (but reduced somewhat by busbar and cable resistance.)

MRBF or ANL fuses are good for some applications. I used class T for my larger and more expensive setup.
My inverters have a breaker built in so I added a fuse at he battery.

 

[Austin68]

Im using lead acid.

 

[Hedges]

In that case most of the fuse types are sufficient; some are pretty inexpensive.
Here's one for bolt type terminals:

MRBF Terminal Fuse Block - 30 to 300A - Blue Sea Systems

Easily and economically satisfies ABYC 7 circuit protection rule by mounting on a 3/8 battery post, battery switch or bus bar.

www.bluesea.com

 

[Austin68]

Thank you very much. I was wanting to use a breaker so i also had a shut off. I appreciate the info

 

[Hedges]

Thank you very much. I was wanting to use a breaker so i also had a shut off. I appreciate the info

Quality high current DC breakers are harder to come by, but there are some.

Product - MidNite Solar

MidNite Solar Product Page.

www.midnitesolar.com

Separate fuse and switch is another option

Single Circuit ON-OFF with Locking Key - Red - Blue Sea Systems

300 Amps continuous rating for outboards and small gasoline or diesel engines.

www.bluesea.com

The following is a quality, low amperage breaker (not enough for the inverter)
Avoid off-brand high-current breakers which look like this; they will overheat and not work right:

187-Series Circuit Breaker - Panel Mount 30A - Blue Sea Systems

Thermal circuit breakers provide heavy duty circuit protection for 25 to 200 Amp loads when switching and circuit protection are both required.

www.bluesea.com

 

[Austin68]

I had found these two, can i get your opion on these,https://www.amazon.com/Low-voltage-...5a249d393b93b&language=en_US&ref_=as_li_ss_tl

https://www.amazon.com/Blue-Sea-Systems-Circuit-Breakers/dp/B0051OWRHE/ref=as_li_ss_tl?dchild=1&keywords=blue+sea+150v+breaker&qid=1607543777&sr=8-4&th=1&linkCode=sl1&tag=adveinaback0d-20&linkId=84bb725151223da1b5c3b3879ac36299&language=en_US

 

[Hedges]

The genuine "Blue Sea" breaker (made by Buss) would be OK.

187-Series Circuit Breaker - Surface Mount 150A - Blue Sea Systems

Thermal circuit breakers provide heavy duty circuit protection for 25 to 200 Amp loads when switching and circuit protection are both required.

www.bluesea.com

The listing you linked uses their name in vain and is half the price. Probably will overheat at well below rated current. Possibly won't trip when it should, fail to protected.

The other one, 63A dual pole, if actually made by "Schneider Electric" as named in the text would be good.
Brand name doesn't appear in the picture. One of the forum members got something like that and the name was branded.
So many counterfeits, it is easy to be suspicious. Compare price to another listing:

Schneider Electric A9N61531 - miniature circuit breaker - C60H - 2 poles - 16 A - C curve

Sales Unit: 1 ST.

industry-electronics.com

DC breakers from Midnight Solar

Product - MidNite Solar

MidNite Solar Product Page.

www.midnitesolar.com

Product - MidNite Solar

MidNite Solar Product Page.

www.midnitesolar.com

Note that "polarized" breakers can only interrupt current flowing one directions, will arc and burn in opposite direction.

 

[Austin68]

I really appreciate your time.