Hi everyone almost completed my solar system for my rv, what is the fuse size required for a 2000 watt renogy inverter with a peak surge of 4000watts and the fuse located at the batteries. My power bank is 2- 100ah renogy batteries connected in parallel. I'm using all 2/0 wires on battery bank and inverter. Using a epever 40 amp solar controller with 4 - 100 amp renogy solar panels connected in parallel to a junction box on roof then down to my controller using 6 gauge wire to controller. Inverter will be a maximum of 2' from the batteries.
Fuse sizing
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John Frum
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2000 ac watts / .85 conversion factor / 12 volts low cutoff = 196.078431373 service amps
196.078431373 service amps / .8 fuse headroom = 245.098039216 fault amps.
Put a 300 amp mrbf or anl fuse as close to battery positive as possible.
Fuse the inverter also at 300 amps at or as close to the busbar as possible
Fuse the solar controller at or as close to the busbar as possible with a 100 amp fuse.
I've assumed that you are using busbars.
I'll leave the pv fusing/disconnect suggestions to someone else.
196.078431373 service amps / .8 fuse headroom = 245.098039216 fault amps.
Put a 300 amp mrbf or anl fuse as close to battery positive as possible.
Fuse the inverter also at 300 amps at or as close to the busbar as possible
Fuse the solar controller at or as close to the busbar as possible with a 100 amp fuse.
I've assumed that you are using busbars.
I'll leave the pv fusing/disconnect suggestions to someone else.
John Frum
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Nope, have another look at the math I did.
Even for a low frequency inverter the surge doesn't usually effect the calculation.
What inverter do you have?
Please post a product link and I will check the specs.
I'm curious why you recommend a 300A fuse instead of the calculated 250A?
John Frum
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I fuse for the wire.
Higher amp fusing generally have lower resistance but that is just a side benefit.
Have you heard the saying, "fuse protect wires and appliances protect fuses"?
John Frum
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Sorry, I think I misunderstood both of your questions.
For the main wire I like to oversize it a bit.
Also not sure how it is where you live but its hard to get all the different wire sizes.
So I generally go 6 awg for 100 fault amps.
2 awg for 200 fault amps
2/0 for 300 fault amps.
I don't go for the in-betweens on the first pass.
For the main wire I like to oversize it a bit.
Also not sure how it is where you live but its hard to get all the different wire sizes.
So I generally go 6 awg for 100 fault amps.
2 awg for 200 fault amps
2/0 for 300 fault amps.
I don't go for the in-betweens on the first pass.
I hadn't heard that higher amp fuses have lower resistance.
But that aside, how did you pick a 300A amp when the wire size isn't known? Given the 200A service amps I would pick 2/0AWG which can be fused up to 350A when not bundled and lots of other assumptions.
And if you are going to pick a really large fuse (that's still safe for the wire) then wire calculate the fault amps at all? My approach has always been to calculate the load (service amps). Pick the wire based on that. Now you have a possible fuse range - the load amps and the max safe fuse size for the chosen wire. You want a good balance in between. Not too close to the load amps to avoid nuisance trips and not too close to the max to avoid overly hot wires (even if still technically safe). A common metric is load amps times 1.25 which is what I always thought your "fault amps" represented. Of course you need to be sure the 1.25 factor gives you a number below the max.
I'm asking to sincerely understand your approach.
John Frum
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it does.
OK, so it seems you round up the fault amps to the nearest 100A and pick from your preselected set of choices. That works. You end up with wires and fuses that may be bigger than necessary at times but that only impacts the wallet, not the system.
John Frum
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Its not my money
Seriously, I over spec these wires because I don't want them getting hot.
I don't know where they are being routed or what flamable thing might be proximal.
I also don't have much control of the wire being used except for the gauge and hoping they get pure copper with 105C insulation.
Also a lot of the folks I help have never done high amperage joinery.
These thoughts rattle around between my ears.
For my own system I have a 1500 watt inverter at 24 volts and I used xhhw-2 2 awg with 130C insulation.
Fully agree. We are here to help but we might make mistakes. I would never be offended if someone points out a mistake in anything I ever suggest.
John Frum
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Yes, you can use pure copper wire 1/0 awg wire with insulation rated for 105C and a 250 amp fuse.
This gives you no margin for error though.
Your wires will likely get hot if you run the inverter near max capacity.
John Frum
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If you use a bigger wire you should use a bugger fuse.
2/0 awg and a 300 amp fuse is fine.
Sound like you are using busbars.
To the best of my knowledge there are no quality thermal breakers beyond 200 amps.
What kind of breaker are you planning to use?
I think you should make a drawing so that we can see the planned topology.
smoothJoey is making sense. The problem is he isn't shouting at you. Rule Number One; Fuses protect wires! I don't know what inverter you have. My 2000W's manual requires 2/0 cable for up to 10 feet.
I only use marine grade cable in van builds, so that is 105C degree. My procedure to select cables and fuses.
#1 Determine the amperes required by the device. (not the surge rating). My 2000W inverter at 12 VDC plus a buffer of 25%. = (2000 / 12) x 1.25 = 208A.
#2 Use the round trip distance from battery to inverter determine the required cable for the needed voltage drop. Using one of the many voltage drop tables on the internet. 4 feet positive and 4 feet negative. Voltage drop chart = 2/0 cable for less than 2% voltage drop.
#3 Use the appropriate ampacity table for your class wire. 2/0 marine single conduit = 330 ampacity. 330A fuse is not available. I pick a 300 amp fuse. Class-T for first catastrophic fuse on LiFePo, MRFB terminal fuses are my choice, or in a pinch, but never for me, ANL.
Note; has anyone noticed the Blue Sea Circuit Wizard seems to give inconsistent results? I used one at GenuineDealz but it is harder to use.
I only use marine grade cable in van builds, so that is 105C degree. My procedure to select cables and fuses.
#1 Determine the amperes required by the device. (not the surge rating). My 2000W inverter at 12 VDC plus a buffer of 25%. = (2000 / 12) x 1.25 = 208A.
#2 Use the round trip distance from battery to inverter determine the required cable for the needed voltage drop. Using one of the many voltage drop tables on the internet. 4 feet positive and 4 feet negative. Voltage drop chart = 2/0 cable for less than 2% voltage drop.
#3 Use the appropriate ampacity table for your class wire. 2/0 marine single conduit = 330 ampacity. 330A fuse is not available. I pick a 300 amp fuse. Class-T for first catastrophic fuse on LiFePo, MRFB terminal fuses are my choice, or in a pinch, but never for me, ANL.
Note; has anyone noticed the Blue Sea Circuit Wizard seems to give inconsistent results? I used one at GenuineDealz but it is harder to use.
