Circuit breaker

[tljones7879]

I have a 1200 watt pure sine wave inverter and wiring a 150 amp circuit breaker between the battery bank and the inverter. The hole for the positive wire on the inverter will accept a 2awg wire, which I have installed. Is it ok to use a 2.0 wire going from the battery to the circuit breaker and a 2 awg wire going from the circuit breaker to the inverter? Thank you! Terry

 

[snoobler]

So...

Battery---2awg---150A breaker---2awg---Invterter

?

Not sure of the concern, but 2awg can handle the presumed ~100A current between the battery and 12V inverter, so that's fine.

Make sure you're not using a cheap Amazon 150A breaker. They either work great, or they're garbage.

 

[Hedges]

Assuming that's a 12V system, so ~ 100A

Wire gauge should be heavy enough to handle whatever the breaker or fuse can deliver, which is more than expected draw from inverter.
Copper wire 2 awg 90 degree C insulation with multiple conductors in a cable or conduit is good for 125A
As individual conductors in free air 2 awg can handle 190A.

I suggest keeping the wires separated by a fraction of an inch, and not tucked under insulating materials.
Most of the wire length should be exposed to some air for cooling.

"2.0" did you you mean 2/0? Certainly 2/0 is preferred for most of the length.
Normally we would put breaker or fuse right at battery positive terminal. In this case, so long as you're sure cable won't get cut by a sheet metal bulkhead or something, you might run 2/0 a longer distance from battery and put the breaker at inverter to keep 2 awg short.

 

[snoobler]

Good catch on 2.0 vs. 2/0. I completely missed that. Agree with the recommendation of cozying up the breaker to the inverter.

 

[tljones7879]

So...

Battery---2awg---150A breaker---2awg---Invterter

?

Not sure of the concern, but 2awg can handle the presumed ~100A current between the battery and 12V inverter, so that's fine.

Make sure you're not using a cheap Amazon 150A breaker. They either work great, or they're garbage.

Ok let me try to re explain. Coming from the positive side of my battery I have a 2 aught red cable going to the 150 amp circuit breaker. On the other side of the 150 amp circuit breaker I have a 2 awg (smaller) wire going to the inverter. The inverter terminal would not accomodate the big 2 aught wire so I went to a smaller wire. The 150 amp circuit breaker is a Truck star brand breaker. If this is not a good breaker please let me know where to get a high quality breaker. Again thank you!

 

[tljones7879]

Also I am using two battleborn lithium batteries, 100 ah each, in parallel . So I have 12v and 200ah going to the 150 amp breaker for the 1200 watt inverter. I hope that is all ok! Lol

 

[Hedges]

All good.
The breaker shouldn't trip under continuous load.
If the wire gets shorted (or the inverter for some reason suffers a meltdown), breaker will trip before wire get too hot and starts a fire.

 

[snoobler]

Agree with @Hedges, but want to circle back to the initial post - if this is a 150A breaker from Amazon, it may not be reliable.

 

[tljones7879]

All good.
The breaker shouldn't trip under continuous load.
If the wire gets shorted (or the inverter for some reason suffers a meltdown), breaker will trip before wire get too hot and starts a fire.

Thank you and snoobler! Glad knowing I am on the right track! I have a Truck Star circuit breaker. It came with the van and the inverter came with the van as well. I looked and on eBay this 150 amp circuit breaker is about $31. If there is a better one that I should be using please advise and I will buy it. Many thanks for this info!

 

[tljones7879]

Agree with @Hedges, but want to circle back to the initial post - if this is a 150A breaker from Amazon, it may not be reliable.

Can you recommend a good 150 amp breaker? Thanks!

 

[snoobler]

Blue Sea Systems, Eaton Bussman, LittleFuse are all quality brands.

Truck Star might be fine, but I can't find anything meaningful about that brand other than other listings on ebay and a handful of minor sites.

 

[bdl]

A data point on the garbage no-name Chinese breakers: I just tested a "200A" marine-style DC breaker from ebay (can you see what's coming?) that overheated and partially tripped after around 5 minutes with a 110A load (inverter pushing out ~1400W). When operating properly the breaker dropped about ~50mV (~5W heat, a little higher than would be nice, but not over the top). After around 3-5 minutes the voltage drop across the breaker started creeping up, passing 100mV and then rapidly increasing from there; the last value I saw on the meter was nearly 250mV and then the inverter tripped out.

The disturbing part was that the breaker did not open (physically nor electrically) - it was still passing current but with a very large voltage drop. Fortunately the inverter low voltage cutout kicked in and shut off the load. At this point the breaker had 8.9V across it (from a 4S / 12V battery).

Maybe the breaker is mislabelled and is in fact a 100A breaker, and it would have tripped if the load stayed on. Or maybe it would have caught fire. No doubt the dodgy manufacturer could care less either way.

 

[Steve_S]

You really want to TRUST your breakers to do their job:
MidNite Solar Products

The "Real Deal" to put between your battery bank & Inverter, NOTE the LUGS are 3/8" for Batt Cables.
CARLING TECHNOLOGIES FA1-B0-917-12A-BG 175 amp 125 volt DC DISCONNECT BREAKER | eBay

Alternately, BlueSea (Eaton & Bussman mostly)
Circuit Breakers - Blue Sea Systems

 

[HRTKD]

When shopping for circuit breakers, be aware that some of them are polarized, meaning that they expect power to flow in one direction. The only breakers I've seen this on are DIN rail mounted circuit breakers. But it's something I now look for every time. Sometimes you have to dig to find this out. I bought a set of Midnight Solar DIN rail mounted DC circuit breakers recently and nothing in the product listing led me to believe they were polarized.

 

[Hedges]

Retailers may not say if the breakers are polarized.

On Midnight's web page, most of the DC breaker listings way polarized or not:

Category Products - MidNite Solar's

MidNite Solar Category Products.

www.midnitesolar.com

Here's one that does not. But at least the picture clearly shows "+" and "-"

MidNite Solar Alternative Energy Products: E-Panels to Inverters

MidNite Solar offers a large variety of alternative energy products from E-panels to charge controllers and inverters.

www.midnitesolar.com

There ought to be a link for data sheet under "Documents" tab, but that has been broken for a while.

It also has a link to their tale of on-the-job learning regarding polarized breakers

http://www.midnitesolar.com/pdfs/MidNite_165vdc_ETLtest.pdf

The AC breakers of course don't say polarized.

If a DC breaker is polarized, it can only be relied upon to shut off with current flowing one direction, not the other. If the application can have current flowing both directions, a non-polarized breaker is required.
Between an inverter/charger would be one, of course.
Between a charge controller and battery is another, because if the charge controller fails current could be dumped into it from battery.
Between PV panels and charge controller is another, if there are more than two parallel strings of PV panels. In the event one PV string gets shorted, all the other strings will dump their current into it, reverse direction.

If OP's "1200 watt pure sine wave inverter" is just an inverter, no charger and no PV connections, then polarized would be OK.

 

[bdl]

Another random tidbit on circuit breakers: even quality breakers will get very hot near their rated load.

I replace the garbage no-name breaker from my previous post with a Mechanical Products MP Series 17 200A breaker. When testing at my system's maximum load of around 2000W (ca. 180A via the breaker) the MP breaker got remarkably hot - the finger test suggests around 50-60C. The heat is definitely from the breaker: attached cabling remains only slightly warm. With about 120mV across the breaker at 180A, that's about 20W of power which would certainly heat things up. Notably the breaker seemed to reach a steady state and did not misbehave in the 10 minutes or so I ran the test for; unlike the no-name breaker which went high resistance without opening.

I contacted MP who responded very promptly and advised the above was a normal condition for 200A breaker at 180A, and that if temperature is an issue in the application a higher ampere rated device could be used.

Anyway, something to be aware of esp. when planning where to mount things.