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Old 11-21-2022, 10:36 PM   #141
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I'm not sure exactly what this breaker is protecting.

A 30-amp breaker seems way too small to be used to protect the whole system, and too large for the individual 12v circuits.

What I've got is a single instant blow fuse immediately in line with the batteries on the positive side. It's sized to protect the main battery cables in the event of a total short. I believe mine is 225 amps (or something like that - not home to go look).

You need to size yours to allow the full estimated current flow plus a bit extra, but not more than the battery cables are rated for.

There are charts online with the common diameter of various cable ratings, and you can use calipers. Not a perfect science due to manufacturing differences. Also be aware that there are metric sizes out there as well our standard.

If you're pulling cables from a vehicle, check out the wiring diagram for the vehicle. Wire size might be listed.
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Old 11-21-2022, 11:01 PM   #142
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Honestly, I’m not very sure either.
I must’ve seen it in a video or on someones else digram so I added it. I don’t think it was brought up here, so I just left it in the diagram.I think it was supposed to open if things pulled too much power then close on its own?

You’re saying I don’t need it and can just add a fuse?
Being that my combined Amp pull is 53 Amps, would I add a 60amp inline fuse?

I was trying to determine fuse sizes for the fuse box.
How much would you round up, if any?
Like the water pump, it’s rated at 16 amps, would I put a 20 amp fuse?

2 ceiling vents have a combined draw of 4 amps.
Would it be a 5 amp fuse or 7.5 amp?
This is of course with all the correct wire ga in place.
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Old 11-21-2022, 11:14 PM   #143
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Fuses are generally sized to protect wiring, not specific devices. Unless the device specifies a particular fuse size use one appropriate for the current carrying capacity of the wire.

Water pumps will usually spec a fuse size. If it's the only thing on the circuit put it at the fuse panel feeding the water pump. If it's on a shared circuit, put an inline fuse near the water pump.
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Old 11-21-2022, 11:32 PM   #144
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Ah yes, I remember you saying the fuses were for the wires.

The water pump I got does not specify a fuse size.
The water pump is fed from a 10ga wire that goes to a switch panel and then the 10ga wire goes to the pump.
So a shared circuit?
Each accessory on the switch panel has its own fuse.
The 10ga wire feeding the switch panel is fused at the fuse box with a 20amp fuse I put.
The water pump is then fused from the switch panel with a 15Amp fuse. I found a calculator online and it’s saying to use a 20amp fuse for the pump.

The calculator recommends a 65 amp fuse for my battery 2ga cables.
Minimum fuse is listed at 53amp.
Maximum fuse is listed as 300+ amps?!

Would you trust this calculator?
If the calculator is correct, I could go with a 70amp fuse, correct?

Baomain ANL-70A Electrical Protection ANL Fuse 70 Amp with Fuse Holder 1 Pack https://a.co/d/694IX9J

https://www.explorist.life/what-size...ctrical-setup/

Thanks.
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Old 11-21-2022, 11:55 PM   #145
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You can use a smaller fuse than the wire calls for, but never larger. In this case the wire from the fused switch to the pump is a dedicated circuit. Use whatever size is needed for the pump, as long as it's not bigger than the wire permits which in this case shouldn't be a problem.
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Old 11-22-2022, 12:09 AM   #146
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Ok, so if the wire or calculator calls for a 16amp fuse (which I don’t think exists in spade fuses) I can use a a smaller 15 amp fuse from the switch panel to the water pump?
And this would be the same for other circuits? Round down and not up?
Rounding up is for wire gauge only..?
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Old 11-22-2022, 02:47 AM   #147
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Rounding up for wire sizes gives you a buffer in capacity. Rounding down with fuses gives you a buffer in protection.
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Old 11-22-2022, 09:39 AM   #148
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Got it.
Thank you.
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Old 11-22-2022, 09:47 PM   #149
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Last question on fuses, how much rounding down is too much?

Example, the pump is 16amps.
Is rounding down 1 amp sufficient to protect the wire? Or do I go to 10amps?

If a system is 19amps, the nearest low amp fuse is 15.
??
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Old 11-22-2022, 10:54 PM   #150
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Quote:
Originally Posted by Serf27 View Post
Last question on fuses, how much rounding down is too much?

Example, the pump is 16amps.
Is rounding down 1 amp sufficient to protect the wire? Or do I go to 10amps?

If a system is 19amps, the nearest low amp fuse is 15.
??
If the pump draws 16 amps, then the circuit wiring and the fuse needs to be able to consistently handle 16 amps. You have to go with the next fuse up from there since there might be a slight surge draw when the pump first starts.

This would likely mean a 20-amp fuse, since that's the next commonly available size. To do this, the wiring in the circuit needs to be suitable for 20 amps as well.

But let's say you used wiring capable of carrying 30 amps on this dedicated circuit. You don't need to, but if you did it would give you quite the buffer in current carrying capacity. There's nothing wrong with putting a pump on a circuit with wiring capable of carrying 30 amps, but to protect the pump's internal wiring it would be a good idea to use an appropriate sized fuse to protect it, hence you'd use a 20-amp fuse.
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Old 11-23-2022, 12:55 AM   #151
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Ok, I thought the fuses were to be lower than what the accessory would try to pull from the wire, so the fuse would blow before the wire burns.

All the wiring I used for each accessory is capable to handle the amp draw + a bit more.

So fuses are to be rounded up?
IE: 2amp draw=5amp fuse. 11amp draw=15amp fuse? Etc etc.
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Old 11-23-2022, 02:00 AM   #152
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It depends. If you're putting a fuse on a shared circuit, the fuse should be rated for less than the wire is capable of handling. In this case you want the fuse to blow before the wires melt down.

But, if you are installing a fuse to protect a specific piece of equipment, and you know the current draw of the equipment, the fuse had to allow for the current to flow. If your pump draws 16 amps and you install a 15-amp fuse it will constantly blow. In this case you round up to the next available fuse size.
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Old 11-23-2022, 09:23 AM   #153
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Quote:
Originally Posted by Serf27 View Post
Ok, I thought the fuses were to be lower than what the accessory would try to pull from the wire, so the fuse would blow before the wire burns.

All the wiring I used for each accessory is capable to handle the amp draw + a bit more.

So fuses are to be rounded up?
IE: 2amp draw=5amp fuse. 11amp draw=15amp fuse? Etc etc.
The fuse must be larger then the draw, no exceptions.
It is a good idea for the fuse to be at least 20% larger then the load to cover surge and higher amp draw due to lower voltage.
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Old 12-21-2022, 10:02 PM   #154
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Hey all, took a break from wiring.
Worked on other stuff around the trailer.
Back to wiring and the fusing makes sense.
No fuses have blown during testing.

120VAC system is done.

12VDC system is almost done.
I wired the converter, fuse box and +/- bus bars.

The wire I used was the one from the car I mentioned previously. I didnít measure it but it was thick and barely fit into the terminals on the inverter, so it should be fine.

12VDC is 99% done. I need to wire the + cable going to the + post on the battery to the on/off switch and wire the trailer 7 pin.

Richard said he uses a fuse between the battery and + bus bar.
Online I see people use the self reseting breaker.
Which is best to use?

I also plugged the converter into an extension cord and it powered everything up!
The converter has 2 small fuses on it.
I donít think another inline fuse is needed between the converter + terminal and the + bus bar correct?

Iíve been hooking my car up to the trailers fuse box to give the interior power so I can have lighting and see what Iím doing.
Since the converter is now wired in, is it safe to plug the converter into an extension to power up the trailer?
Or will it damage the converter?
I donít have batteries yet.

Hereís how it looks so far. Still missing my grounds going to the frame.
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Old 12-21-2022, 11:06 PM   #155
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...Richard said he uses a fuse between the battery and + bus bar.
Online I see people use the self reseting breaker.
Which is best to use?...
The purpose of the fuse is to act as a cutoff in case of a catastrophic short. In a situation like this, you don't want the thing resetting itself or it will just keep cycling till something fails. Better to use a fuse for this so it stays cut off until you identify and fix the problem. This fuse should be rated for more than the max current you'll pull from your batteries, plus a small margin for startup load surge, but never for more than your battery cables are rated to handle.
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Old 12-22-2022, 12:51 AM   #156
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Thanks for pointing that out. It makes perfect sense.
Currently I’m at 53 total amps.
I plan to add a few more lights so it should put me at maybe 55amps. I will go with a 65 amp fuse that the calculator recommends.
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Old 12-22-2022, 04:39 AM   #157
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I actually can’t find a 65 amp fuse that’s recommended.
I see 60 amp and 70amp.
Which is ideal for a 55amp draw?
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Old 12-22-2022, 05:28 AM   #158
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The 70 should be fine.
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Old 12-23-2022, 09:34 PM   #159
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Ok thanks. I ordered a 70amp fuse and fuse holder for it.
I added the breaker box ground to frame today.
I also added the trailer skin ground.

How big should the wire on the trailer skin ground be?
I used a spare piece of Romex 12/2 for the skin ground.
I attached it to the skin and then pushed it into the grounding lug that the breaker box ground cable went to.

To verify the entire trailer skin is grounded, would I check continuity between the skin ground at the front of the trailer when the ground wire it and the back of the trailer?

I can also spray some paint over the grounding lugs now since they’re touching the metal frame right? To prevent rust.
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Old 12-23-2022, 10:30 PM   #160
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Ok thanks. I ordered a 70amp fuse and fuse holder for it.
I added the breaker box ground to frame today.
I also added the trailer skin ground.

How big should the wire on the trailer skin ground be?
I used a spare piece of Romex 12/2 for the skin ground.
I attached it to the skin and then pushed it into the grounding lug that the breaker box ground cable went to.

To verify the entire trailer skin is grounded, would I check continuity between the skin ground at the front of the trailer when the ground wire it and the back of the trailer?

I can also spray some paint over the grounding lugs now since theyíre touching the metal frame right? To prevent rust.
I can't address your "should" questions, but I can say what I did...

My grounding wires match the circuit they are grounding. For example, my breaker panel is fed with 8 ga wires so the ground to frame is 8 ga, etc.

All points in your shell and chassis should have continuity to the grounding wires, at least mine do.

My grounding lugs are protected with a good smear of anti-corrosion grease designed for electrical connections. I'm not sure that paint is the best option as it would would make future changes or reseating the connections difficult. It will also chip off and allow corrosion to get trapped behind the paint - things will look good but be secretly rotting away behind the paint.
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