What guage wire? Battery to Fuse Panel

[Miriam C.]

Whoa, whoa, whoa! Let's clarify a bit. I will have 6 fuses, each rated at 10 amps. Assuming everything is running at the same time (worst case scenario and unlikely) there will be a temporary draw of 10 amps off the battery. Ordinarily, there will be way less than that. I'm talking about a few lights and 12v outlet or two. This wire will be exposed for the most part (run through cabinets).

I think I'll go with 8 guage to the panel and leave the old 110-style wiring in place.

But it was great information huh! I bet #10 will do fine iffin ya wanted.

[bdosborn]

I agree with Miriam, a #10 with a 30A fuse and you're good to go.
Bruce

[madjack]

I agree with Miriam, a #10 with a 30A fuse and you're good to go.
Bruce

..that is what I use...think about it...size the wire to the fuse you are using(or vice versa)...a 2,4,6 ga wire with a 30 A fuse is a waste of money and resources...ya know.........
madjack

[amblt]

I'm curious to know why some are recommending such close calculation of wire size, as if oversizing would be a sin. Surely there is no seruious weight penalty, and it can't be that hard to make your holes and raceways of a slightly larger dimension. Is the cost factor so great that we need to run close to the safety margins? I must be missing something here.

[bdosborn]

I'm curious to know why some are recommending such close calculation of wire size, as if oversizing would be a sin. Surely there is no seruious weight penalty, and it can't be that hard to make your holes and raceways of a slightly larger dimension. Is the cost factor so great that we need to run close to the safety margins? I must be missing something here.

Oversizing isn't a sin, it just wastes money. Unless you have an inverter, a 30 amp wire is plenty for the typical teardrop. Besides, a typical battery would only last an hour or two at 30 amps anyways. What are your loads? That's the way you should size wire, for the loads in your trailer

Bruce

[Socal Tom]

Oversizing isn't a sin, it just wastes money. Unless you have an inverter, a 30 amp wire is plenty for the typical teardrop. Besides, a typical battery would only last an hour or two at 30 amps anyways. What are your loads? That's the way you should size wire, for the loads in your trailer

Bruce

I will argue both sides of the argument here... Moderate over-sizing is probably a good idea. All these charts are based on new wire. If you want to build some extra life into your system, then a little over-sizing will compensate for some moderate corrosion. On the other hand... These charts are all based on continuous loads, and most of us won't have EVERYTHING on at the same time, so you will rarely see peak load, and when you do it won't be for very long in most cases, so sizing it for your peak load is already over-sizing vs what your system will see on a continuous load.

Did I confuse anyone yet?
Tom

[bdosborn]

Did I confuse anyone yet?

So what size wire do you recommend as neither undersized or oversized?
Bruce

[Socal Tom]

Did I confuse anyone yet?

So what size wire do you recommend as neither undersized or oversized?
Bruce

I would set my wire size based on the breaker nearest the battery. If 60 amps, then #8 based on the charts at the 2nd post, if 30 amps then #10. If it were me I would go with the 30 amp breaker. I don't want the risk of 60 amps shooting through a short in my wiring, and 30 amps will probably handle most anything he wants.
If you install something with a very high demand like a large inverter, then I would run a dedicated line to it with its own breaker.
Tom

[bdosborn]

Sigh...

Here's how I would do it:

Add up all the amps of all the electrical devices in the trailer. Add 25% and that is your design load. Use that number to pick a wire and fuse from the chart below. Now you have a wire that is designed for your total trailer electrical load and not just a WAG. No waste, no overloading and no nuisance trips. I'd feed an inverter directly from the battery on it's own fuse like you said as the required wire is usually too big to terminate on a fuse block.



However, most people don't want to learn how to size wire and fuses, they just want a quick answer. Hence the 30 amp wire recommendation as it will work for 95% of the teardrops out there. I know this because I have a Trimetric meter in my trailer and track my power usage; 30 amps should be plenty for most.

BTW, the reason you use the chart I posted is that its for the wire you buy at the Home Center as opposed to marine wire, high temperature automotive wire or generic AWG wire. Yes, its conservative but it's very SAFE.

Bruce