inverter fuse/breaker

starcraft69 wrote:
I am purchasing a 3000 watt inverter and wondering should i use a ANL 300amp fuse or a 300amp breaker between batteries and inverter?

For my 2000W inverter/charger, I use this 300A magnetic-hydraulic DC breaker from BlueSea.

I used to use a fuse, but if they blow (and they do), then you had better carry spares.

The owner's manual for my Vector SST MSW inverter says to use ANL fuses for all wattage inverters in that class. Some not too clear wording that the ANL fuse "goes with" the surge rating of the inverter for when it will blow.

Specification table says for a 3000w(6000 surge) to use a 500a ANL fuse. Wire should be 2/0 for up to 6ft and 250mm for up to 10ft

With my 2000w that says use the same 500a ANL fuse, I used their "kit" wiring of two -three ft #4 instead of a single 1/0 at pos and neg (has two of each) so my choice at the pos battery post was:

A. put a 500 ANL fuse to the post with the two #4s to that fuse, or
B. put a 250 ANL fuse on each wire to the post (what I did)

DrewE wrote:

starcraft69 wrote:

This is what i was thinking Is 300amp breaker the right size?

What size wire will you be using? That's the main purpose of the fuse--to prevent a fire from the wire overheating in the event of a short circuit.

300A is a reasonable ballpark value, though larger might be better as most inverters have a surge capability somewhat beyond their nominal rated capacity. (Well, decent inverters do; all bets are off for questionable unknown brand inverters from overseas.)

Edit: The inverter instructions may have some recommendations on power lead wire size and fusing.

I am planning on using 1/0 wire

MrWizard wrote:
No I don't think it's going to handle 8000 amps short
Why should it
You want it to trip at 300

What do you think will a 300a breaker work and be safe with 1/0 cable ?

I would call 4/0 minimum, may need 250MCM if you expect full performance including the surge. Also may depend on length.

1/0 is more for 1500/1800 watt inverter.

Or is this one of those cheapos that really only produce 50% to 70% of rating?

Class T will pass 2x current for some time before it opens. A bit of a slow-blow fuse so I would keep it a bit tight.


Note 2x rating takes a full minute to open.

I would go 200 max class-T or 250 ANL on 1/0 wire.

Custom cables made here up to 4/0:
http://www.genuinedealz.com/custom-cables

I just reran all my compartment battery cables after getting a new 250 amp alternator and replacing batteries(6-6 volt) and since doing it myself, I used 4/0 for everything including replacing a 300 amp T fuse. There not cheap so if there is an option to use a resettable device, I'd go for it.

AC continuous duty would be 150amps
but this is long wire runs, possibly in metal conduit
for short inverter runs i think it should be OK

i have 2ft runs of #2 fused with a 200amp breaker, but load seldom exceeds 90amps
this is on a 2KW continuous 3KW surge inverter

i've got some bigger wire someplace to replace it, but i sized it to the expected load, not max capability, it can run the coffee maker or MW without overheating the wire

1/0 isn't big enough for a 3 kW inverter. I would think you would want 4/0 if you're going any distance at all. A 3,000 watt inverter at 12 volts will be drawing 250 amps without taking efficiency into consideration. Figure it's only 80% efficient and now you're drawing 312 amps. If the voltage sags below 12 volts, which it likely will, you would be drawing even more current. 3/0 is rated for 350 amps in free air (less if in conduit). IF you're really going to draw 3 kW from the inverter I would use 4/0 cable and a 400A breaker or class T fuse. The breaker that TechWriter liked to is rated for a 5,000 A interrupt ratting at 48v. It doesn't say what it would be at 12v but likely substantially higher. The only way to find out what your battery bank's fault current is would be to find out from the manufacturer.
Carling Technologies makes lots of high current breakers resold by many of the inverter manufactuerers. Their F series is rated for up to 50,000 Amps of fault current up to 125v DC.
As difficult and expensive as a suitable 400A breaker may be to find I would probably just use a fuse unless you will never be using your inverter at it's full capacity.

starcraft69 wrote:
Is 300amp breaker the right size?

You may want to consider upping the input voltage to 24 or higher on a big inverter. No wrestling with cables as big as your thumb.

2oldman wrote:

starcraft69 wrote:
Is 300amp breaker the right size?

You may want to consider upping the input voltage to 24 or higher on a big inverter. No wrestling with cables as big as your thumb.

x2 on this ... sounds like OP already bought the hardware though