120 Volt System

[Glennman]

I'm getting ready to install my 120V system. I just picked up a 6 space, 12 circuit, breaker box from Home Depot. I have some 14g and 12g wire laying around the shop. Boy is that stuff expensive! My question today is, do you guys usually...
1. Run all 12g with 20 amp breakers everywhere, or...
2. Mix it up with some 20 amp breakers and corresponding 12g wire and some 15 amp breakers with corresponding 14g wire (depending on load)? or...
3. Do you run all 15 amp circuits and corresponding 14g wire?
My biggest users will be 12,000 and 9000 btu mini splits and probably the refrigerator (a 10 cu ft all electric model that probably doesn't have a defrost feature). I'm thinking it would be cleaner to run all 12g wire and all 20 amp breakers, but I would sure save a lot if I could run all 14g wire. I haven't researched the amperage of the mini splits or the refrigerator yet, but if they will work on 15 amp circuits, I just might go that route. However, if all 15 amp is "cutting corners", then by all means, I will run all 20 amp, or a mixture of both.

I know this is a lot of questions for one post, but at this point I am only trying to get a flavor of what people typically do. I will be planning on a solar system and probably Victron equipment. The range, water heater and main source of heat will be propane (and a CDH), so since I am not going all electric, my system will be fairly minimal. Thanks to everyone in advance.

[richard5933]

In my experience, it never fails that someone will want to plug that space heater or toaster into the outlets which you made 15a, resulting in a blown circuit or worse.

There are not that many outlets in a bus conversion. My thought is that they should all be on 20a circuits to allow for maximum flexibility later on.

All our circuits in my bus are 20a except the one which runs the lighting. Nothing can be plugged into that circuit so it is a closed system with a known load. All the others are either carrying heavier loads or have outlets.

This allows us to plug the toaster in on the dinette table outlet or move the coffee maker up front if we want, or to plug in a space heater or dehumidifier in any space we need.

[buswarrior]

My vote is to upsize wiring beyond the minimum standards, especially to high amperage devices, like the AC and heat.

We aren't wiring a home, with a healthy transformer just outside somewhere.

What happens when the campground voltage drops during the heat wave?
The generator can't keep up voltage? The inverter can't keep up voltage?

Up goes the amps to compensate, and up goes the heat, in the cabling...

You may continue to protect the device with the recommended smaller circuit breaker, no offence is committed by putting big wire and a smaller breaker.

Electrical fires take lots of RVs.

A small investment allows one to declare, "Not MINE!"

Happy coaching!
Buswarrior

[sledhead]

I would go the 20 amp route for all or like said a 15 amp run for led lights

I remember the old 15 amp receptical  and you could not plug in a toster and a 1 cup coffee maker at the same time . alls good though with a 20 amp
my coach has all 20 amp and I never trip a braker

for sure use 20 amp for the split units

[chessie4905]

always use 20 amp. Never know the future loads applied. May not hurt to run 10ga. for any roof airs to counter load with low voltage. Especially with the 18,btu. ones.

[dtcerrato]

Our only 15A CB (all others are 20s & 30A) is for the HE rooftop AC as stipulated by the manufacturer. It eases impact on the AC because the breaker takes the trip before the AC is overheated, etc.

[Jim Blackwood]

I think for reasonably short runs which they all would be in a bus, 12 ga wire will handle a 30A breaker so it's pretty easy to overspec the wiring for safety's sake. Nothing bigger than 14ga and 15A is needed for any lighting circuit. So the usual division is 14ga for lights and 12 ga for outlets. Using 14 ga for any outlets can lead to regrets and there's not much point in going smaller than 14ga for anything.

Jim

[Glennman]

Sounds like there is a consensus on the 12g/20 amp circuits throughout with exception of lighting. Sounds like a great plan. I guess my thinking was that if a space heater with a 14 gauge cord was plugged into a 20 amp circuit, that the cord could melt before the breaker would pop, but I suppose the protection is for the wiring in the walls, not the cord from the unit to the outlet.

Thanks all, and away I go!

[sledhead]

never understood why most cube type heaters have such a small gauge wire to the plug . it gets warm if you use the heater on high . for that reason I never leave the coach with a cube heater on hi and low or 1/2 power is a lot safer

[fortyniner]

Normally I select wire size have less than 3% drop at the max continuous load. Then pick a breaker to support that load.   

But since household breakers are usually 15 or 20amp I use 14ga/15a up to 25'
and 12ga/20amp up to 25'

This is a nice summary:
https://www.thespruce.com/matching-wire-size-to-circuit-amperage-1152865

[dtcerrato]

@sledhead
Know what you mean on cube heater cords similar to iron, toaster, electric skillet, etc. cords. My guess is they fall under a different category as "soft wired" but do have very high temp rated insulation on them.

[sledhead]

I think the small cords are installed so people will not use then for full time heat . but they do and you hear about cube heater fires all the time

[chessie4905]

A lot of those fires, including toe heaters in conversions are from dust accumulation. People don't  blow these out regularly. You would be surprised how much accumulates in them.

[dtcerrato]

The number one cause of fires by any kind of heater, electric, wood stove, fuel, etc. is when they're ran in close proximity to combustibles with that being said the number one causes in combustibles are drapes, curtains, blankets, carpet, furniture, etc. Common sense plays a great role here. As far as internal accumulation of dust in the heater - if & when it catches fire - if it is not in close proximity to combustibles - little problem that will burn itself out but these heaters should be maintained.
Common sense should prevail but ignorance & or stupid can be in that equation.

[Fred Mc]

I didnt know toasters cam any larger that 15 amps.