Newbie on breaker size

[LeonLu]

Hi sorry for the question. I try looking around and even that sizing chart. It didn't make much sense for me. I purchased this 1600W HYBRID 12V 80 amp mmpt inverter.

But the step by step instructions are horrible. The YouTube video is good, but it the 10kw one.

I have only two 200W running on parallel. Due to space I might only add 1 more one day. From my understanding I don't need a fuse. But do I need the breaker here? If so what size. And if possible can you show me how you got to that solution? Ac breaker I assume. Running 10 awg

Same question for my DC battery size. I'm running it on 4 awg for 12V 280 Ah size... Is this where I add the DC breaker? I forgot where but I was somehow lead to believe I need a 40amp one.

This is very different from my first setup, which kit didn't have any breaker at all. I didn't think it was this difficult .

 

[sunshine_eggo]

Fuses/breakers are sized per the conductor, 1.25X (round up), e.g., if your wire is rated for 100A, you select a 125A breaker.

It's not clear if your are talking about the PV or battery side of things.

If PV, you only need a fuse/breaker if you have 3 or more panels in parallel.

If battery, for 1600W:

1600W/12.8V/.85 = 147A (2/0 cable)

147A * 1.25 = 183.75A, round up to 200A

Since you're only using 4awg, it's only rated for 70A @ 60°C, but there is higher rated 4 available.

70A * 1.25 = 87.5A. Probably bump up to 100A.

 

[LeonLu]

Hi, Ty for your reply. The PowMr unit book stated 4 awg. The port itself on unit was one of those kind you place cable in directly. Then screw down. I wasn't sure if getting a 2/0 would allow it to fit.

I think I was a bit confused. It mentioned 10 amp breaker. I now understand the 10 amp is to power my power strip / plug port(AC out put).

So since I'm using two panel, my PV don't need a breaker nor fuse . I'll look up more video to understand the breaker a bit more for PV. It won't hurt to add a breaker later on. Easier to safety disconnect power.

Ty for your math. I was very off then aiming for 40A breaker. I'll guess my project is on hold until new one comes.

 

[Rednecktek]

If it's designed for 4awg then good luck cramming a 2/0 cable in there. The 4awg is plenty for the 80a of output.

As for the breakers, you need to get DC rated breakers fir both ends. The breaker on the output side of the controller can be 100-120a, whichever is easier to source. The breaker on the incoming side only needs to handle the amperage of your strings, and it's more of a handy disconnect than anything else.

 

[LeonLu]

Ya, Ty. I thought as much it would not fit. I didn't risk it and already order the 4 awg.

When you say breaker for both ends. You mean a dual pole one right?

If needed PV to inverter breaker. My imp is 10, so IF I do 3 panel in parallel. I'll need 30-40 amp breaker...to my understanding.

 

[sunshine_eggo]

If it's designed for 4awg then good luck cramming a 2/0 cable in there. The 4awg is plenty for the 80a of output.

As for the breakers, you need to get DC rated breakers fir both ends. The breaker on the output side of the controller can be 100-120a, whichever is easier to source. The breaker on the incoming side only needs to handle the amperage of your strings, and it's more of a handy disconnect than anything else.

80A the MPPT output. It's a 1600W 12V inverter.

1600/12.8/.85 = 147A

If it's UL rated battery cable, yes, that will work:

4 Gauge (4 AWG) Battery Cable with Ends OFC Copper Flexible Stranded UL MTW/THW/SGT

www.batterycablesusa.com

If it's home depot 4awg, it won't.

 

[LeonLu]

The 4 awg pure copper worked. I don't think there was any room left if I go 2/0. It was pretty tight.

 

[sunshine_eggo]

The 4 awg pure copper worked. I don't think there was any room left if I go 2/0. It was pretty tight.

Again, it's specific to the rating of the CABLE. Did you purchase UL listed cable equivalent to what I linked?

 

[LeonLu]

Oh, that was you ment. Cable isn't UL but according to sellers it was rated at 150 amp. I didn't know cable can be UL rated too.

 

[sunshine_eggo]

Oh, that was you ment. Cable isn't UL but according to sellers it was rated at 150 amp. I didn't know cable can be UL rated too.

Welding cable and battery cable are different things, but they are often lumped together. Specs for welding cable are higher than for battery cable due to the intermittent nature of welding.

That's what you're going to use, so 150 * 1.25 = 187.5. Round up to the next common size.

 

[LeonLu]

But didn't your first post you already mention I should just get the 100 amp breaker? I know the cable is rated higher.

I understand a bit better now, bms rated high. You then go off cable amp rate to match.

Last question then. If I'm not planning on doing extremely high draw. Do i even need a high amp breaker? Or we need it so the inverter won't be starve on actual power draw?

 

[sunshine_eggo]

But didn't your first post you already mention I should just get the 100 amp breaker? I know the cable is rated higher.

First post:

Fuses/breakers are sized per the conductor, 1.25X (round up), e.g., if your wire is rated for 100A, you select a 125A breaker.

I understand a bit better now, bms rated high. You then go off cable amp rate to match.

Last question then. If I'm not planning on doing extremely high draw. Do i even need a high amp breaker? Or we need it so the inverter won't be starve on actual power draw?

Why waste money on a breaker you'll trip if you forget to never exceed some low number?

 

[LeonLu]

Why waste money on a breaker you'll trip if you forget to never exceed some low number?

That makes so much sense. I'm but frog in a well here, one track mind. My only concern was to power my window AC. But that would make sense if ever need to go a bit bigger.