What size breaker(s)?

[Mark Freedom]

Damn this is a camping trailer . I am not going to live in it or spend anymore time in it than I have to I prefer the outdoors

It's a lot easier to wire it all up right the first time, than going back and tearing out walls to do it right later.
Makes no difference to me what you do as far as that goes, use a flashlight for all I care, BUT you did ask for advise here didn't you?

[starleen2]

I am fine wih safety . I wonder if one really needs electric frige electric oven micro wave AC electric heaters TV s Dvd players, blenders , and particularly generators . I would suggest staying home.

not to pick a fight or something, I take those things because sometimes we stay for weeks on the road doing mission work and we need to be self sufficient. The areas that we go into sometimes do not have anything and you have to bring it with you - and I'm not talking about camping. I have a 15, 20, 30 amp setup and can run of 12 volt inverter if needed. not much electricity or ice when them hurricanes hit the coast! but how else are you gona cook and keep supplies cold - Ohhh now the picture become a little clearer - there are even some on this forum who used their tears as evacuation shelters to get out of harms way. Ok enough rant - just be safe aound electrical circuts and design what you anticipate the tear to be used for. this is our second build and we learned from the first - had a lot of told you so's - but we listened and now our second is better than the first just my 2 cents

[chesterlion]

I didn't mean to open up a can of worms. I just wanted opinions on the size circuit breaker I should use. I agree with Mark that if I would have had the opportunity to do it the first time I would have done it differently. I bought the woody new from a guy who built it the way he wanted. My main concern was for safety then convenience. I think Diver is just a little more primitive than some but he has his ideas also. Thank you all for weighing in. I think I'll stick with my 20 amp breaker and as madjack said monitor the number of amps I'm using at one time. By the way - is there a chart that tells generally how many amps things reqiure. I know it says on the appliance but it might be nice to have it compiled and posted in the trailer.

[Mark Freedom]

some good info here
http://www.ccis.com/home/mnemeth/12volt/12volt.htm
http://www.ccis.com/home/mnemeth/12volt/12volta.htm

[Reddiver]

Hey thanks for the information. I am just fooling around sorry.

[Miriam C.]

I didn't mean to open up a can of worms. I just wanted opinions on the size circuit breaker I should use. I agree with Mark that if I would have had the opportunity to do it the first time I would have done it differently. I bought the woody new from a guy who built it the way he wanted. My main concern was for safety then convenience. I think Diver is just a little more primitive than some but he has his ideas also. Thank you all for weighing in. I think I'll stick with my 20 amp breaker and as madjack said monitor the number of amps I'm using at one time. By the way - is there a chart that tells generally how many amps things reqiure. I know it says on the appliance but it might be nice to have it compiled and posted in the trailer.

I haven't seen a chart and that might be because there are so many different sizes of all most everything in the US.

No can of worms here just the Electric forum.

Glad the picture helped someone. I preach pictures a lot but it was hard to remember to take them.

[BPFox]

Do you have a chart at home? Perhaps in the kitchen so you know just how much juice it takes to make that toast or coffee. The chart would be just one more thing to worry about. If you use a 20 amp breaker you will be ok since you are using 12 ga wire. Take that off your things to worry about list. You said in your original post that you are only going to have two receptacles both of which will be GFCI protected. That's one more thing you can take off your things to worry about list. With only 4 places to plug stuff in, I doubt you will ever blow that breaker. Now just don't run the blender while using the blow dryer while using the toaster while brewing coffee and you should be just fine.

[Mark Freedom]

Do you have a chart at home? Perhaps in the kitchen so you know just how much juice it takes to make that toast or coffee. The chart would be just one more thing to worry about. If you use a 20 amp breaker you will be ok since you are using 12 ga wire. Take that off your things to worry about list. You said in your original post that you are only going to have two receptacles both of which will be GFCI protected. That's one more thing you can take off your things to worry about list. With only 4 places to plug stuff in, I doubt you will ever blow that breaker. Now just don't run the blender while using the blow dryer while using the toaster while brewing coffee and you should be just fine.

Putting an over-sized breaker in is defeating the purpose of having a breaker, unless of course you just want to make sure it kicks off after it's killed you.

[madjack]

Mark, putting a 20 amp breaker on 12ga wiring is not "an oversized breaker", since 12ga wire is rated for that amperage...remember that breakers are more for protecting the wire than the appliance.......
madjack

[Mark Freedom]

Mark, putting a 20 or 30 amp breaker on 12ga wiring is not "an oversized breaker", since 12ga wire is rated for those amperages...remember that breakers are more for protecting the wire than the appliance.......
madjack

Breakers are for protecting the person first, and the circuit secondly.
In addition the length of wire also plays a great role.
You select the size of breaker and wire for the load it will control based on the length of the run and the appliance/machine/whatever amperage rating.

IF you oversize a breaker, and the wire melts to a metal surface, then it is highly likely that the person touching that metal surface will be electrocuted before the oversized breaker kicks.
Codes are there for a reason.

If you're going to slap a 30 amp breaker in a 15 amp circuit, then why waste your time and money.

[madjack]

Mark, putting a 20 or 30 amp breaker on 12ga wiring is not "an oversized breaker", since 12ga wire is rated for those amperages...remember that breakers are more for protecting the wire than the appliance.......
madjack

Breakers are for protecting the person first, and the circuit secondly.
In addition the length of wire also plays a great role.
You select the size of breaker and wire for the load it will control based on the length of the run and the appliance/machine/whatever amperage rating.

IF you oversize a breaker, and the wire melts to a metal surface, then it is highly likely that the person touching that metal surface will be electrocuted before the oversized breaker kicks.
Codes are there for a reason.

If you're going to slap a 30 amp breaker in a 15 amp circuit, then why waste your time and money.

...thank you George......................................................

[Elumia]

Boy do we miss George (not really).... I don't want to stir the pot too much - nor be another George.

Mark F, I think you have it turned around. Circuit breakers are designed to protect conductors. It makes perfect sense too. Since one can't know what devices are going to plugged into a circuit, the breaker limits the amount of current than can be drawn through the conductor, and also protects against short circuit. The only way a circuit breaker is "over-sized" is if the wire is undersized for the current rating on the breaker, for example, using a 50A breaker on 12 Ga wire.

Remember that 12V DC circuits have 10 times the current as 120V AC circuits for the same wattage.

A GFCI is designed to protect people. Surge protectors are used to protect equipment. You can have these features designed into specialty breakers or in separate devices such as power strips or GFCI outlets.

Siemens has a nice explanation on their web site, in short:
The protection function is not quite so easily understood. What is a molded case circuit breaker intended to protect? What can an over-current protective device be expected to do and what is beyond the scope of its design? Sec. 240.1 (FPN) of the NEC has the following to say about over-current protection:
Over-current protection for conductors and equipment is provided to open the circuit if the current reaches a value that will cause an excessive or dangerous temperature in the conductors or conductor insulation.

So, circuit breakers are intended to protect conductors (insulated wires) by opening automatically before damage is caused by excessive temperatures. This protection applies to the permanently installed wiring of homes, offices, and industrial buildings. In protecting these wires, over-current protective devices reduce the risk of fire, personal injury, and damage to equipment and property
https://www.sea.siemens.com/reselec/pro ... rpose.html


MJ's design uses breakers designed for supplemental protection (UL1077 compared to UL489 which is for Branch circuit protection). I assume he is relying on the breaker at the campsite to protect upstream of their connection and his main fuse is protecting the extension cord that connects the trailer to the post, while his push button breakers are protecting the wires between what he connects inside the trailer.

Needless to say, selecting circuit breakers and fuses can be a complicated process. In addition to current ratings, there are trip curves (thermal) and interruption (short circuit) ratings.

I've only sold the various circuit protection products and am not an engineer. I gave the engineers the information they needed to make decisions that would allow their equipment meet the codes where they were to be installed and offer the protection they required.

In what I have seen, I will put in a molded case UL489 breaker (household style) to protect what comes in the trailer and then use smaller supplemental protection inside the trailer.

As always, it's your trailer, make the decisions you are comfortable with.

Mark

[BPFox]

The bottom line here folks it that a 20 amp breaker is exactly the right breaker to use to protect 12 ga. wiring. The breaker is not there to protect the person. It does not perform that function in your house and it won't perform that function in your trailer. The GFCI on the other hand is there to protect you and that's all it does.

That said, I'm kind of curious where you got the idea I was suggesting an oversized breaker? I have read and re-read my post and I am willing to bet my electricians license that it is spot on accurate. Could you please point out for me that part that is wrong. Thank you.

[Mark Freedom]

I guess I didn't explain myself very well.
It protects the person by tripping before the insulation on the wire melts causing a dangerous situation to develop.

If you read back on this thread you have a guy wanting to run 12-2 to a 70 amp panel to feed the trailer.
People being what people are, it's only a matter of time before that 70 amp service is full of breakers pulling twice the amperage that the feed will handle.
This seemed to be ok with madjack.
So be it, it ain't my ass on the line.

[BPFox]

Read his post again. It's a 70 amp panel not a 70 amp breaker. He can use a 200 amp panel if he want's to. His original question was "what size breaker should I use?" Let me see here. He is going to plug his 20 amp rated extension cord into a 20 amp power panel and he is wiring his single circuit two receptacle system. The answer to his question is 20 amp breaker. Why is he using a 70 amp panel? Because he could not find a 30 amp panel. The size of the panel only indicates the maximum for the panel. It has nothing to do with the breakers or the wiring.