Fused Confused

[UGT]

Am a novice. Read lots lof stuff trying to figure the correct fuse (battery bank to inverter) for my system and still not sure. Sorry. I have a solar back up system for my house. 1600 watts solar panels on the roof, (3) LiTime 24v 200W batteries in parallel. 24V Giandel 3000W inverter with output of 120V, 25A, 3000W. Wires from the battery bank to the inverter are 2/0 AWG. Please can you help me? Thanks.

 

[mikefitz]

175 amp fuse, Bussmann classT or HRC fuse with quality fuseholder.

 

[JK14]

Fuse sizes just have to fit between 2 extremes: 1) Stay small enough to keep downstream wires from melting their insulation, and 2) be large enough to allow the downstream components to max out without tripping the fuse unnecessarily.

1) A 2/0 Wire in free air with assuming 90 deg C rated insulation can max out at 300A, (if insulation is only rated at 60C, max is 225A).
2) A maxed 3000W inverter from a 24 Volt bank uses 125A, but when the battery volts are down to 22 it will use 136, but because inverters are just 90% efficient, it will use 152A, then adding 25% headroom suggests a minimum fuse of 189A (Mike's 175A will also probably work and not nuisance-blow).

So your best range to work from is ~190 - 250

 

[UGT]

Fuse sizes just have to fit between 2 extremes: 1) Stay small enough to keep downstream wires from melting their insulation, and 2) be large enough to allow the downstream components to max out without tripping the fuse unnecessarily.

1) A 2/0 Wire in free air with assuming 90 deg C rated insulation can max out at 300A, (if insulation is only rated at 60C, max is 225A).
2) A maxed 3000W inverter from a 24 Volt bank uses 125A, but when the battery volts are down to 22 it will use 136, but because inverters are just 90% efficient, it will use 152A, then adding 25% headroom suggests a minimum fuse of 189A (Mike's 175A will also probably work and not nuisance-blow).

So your best range to work from is ~190 - 250

My 2/0 wire is 105 deg C rated. Please how does that change the figures. Thanks

 

[DIYrich]

My 2/0 wire is 105 deg C rated. Please how does that change the figures. Thanks

Connections also have to be rated for 90c. Most are not. 175 Amp as recommended, or 225 Amp if you want the larger size class t fuse.

Note: I would consider class t fuse as slow blow. They can allow 150% for a few minutes (according to Blue Sea specs).

 

[SamDeleted]

My 2/0 wire is 105 deg C rated. Please how does that change the figures. Thanks

degrees C is the temperature the insulation is rated for , yours is rated even higher than the 90c JK14 was talking about, yours can run hotter/carry more amps

what he said still applies the same , it just happens your cable is better and can do even more than that .

 

[Mattb4]

I like to size my fuses from the battery to inverter using two fuse holders (one for the negative and one for the positive.) At the fuse holders I size a fuse for maximum load I expect to carry in the circuit. Example I run a 3000w inverter my fuse is 125a for 24vDC. Could it blow if I pulled up to the 3000w? I certainly want it to. The other fuse is to protect the wire and is sized larger than the circuit protection fuse.

Sizing small can mean losing a fuse. Sizing large can mean losing an expensive inverter.

Understand that my choices on this are not what the experts recommend.