Electrical - adding AC wiring to 12 volt system

[Cat futrell]

Ok, I understand that the circuit power drawn may not exceed the size of the sub breaker (it will trip) and that the total of all sub breakers my not exceed the total of the main breaker (or it will trip). In our case that is 30 amps. If we put the converter on a 15 amp breaker and the converter only pulls 6 amps, does that mean that the left over 9 amps are available to other sub circuits in the box?

[GPJ]

Yes. That is correct - the 9 A is available to other circuits.

[Thomas G.]

Originally Posted by GPJ

Yes, I believe that is what he is saying........

Yup

Originally Posted by GPJ

Yes. That is correct - the 9 A is available to other circuits.

Yup

[honda03842]

Our Scamp came with a 30 amp cord and two 15 amp breakers.

We added a number of ac outlets for convenience, actually I think we have 10 ac outlet pairs and increased the breakers from two to four. That means minimally 2-3 outlets are on each breaker. The reality is that we rarely use more than a couple of outlets at any one time.

When we're home in the summer we run our trailer on 120 VAC on a standard 3 prong 20 amp circuit. We are fully capable of running the whole trailer on a single home circuit including our power convertor, refrigerator (we never shut it off) and even our air conditioner. In this configuration we have never tripped a house breaker.

This home configuration means that we use a 30 amp to 20 amp plug convertor. This is used more frequently than the 50 to 30 amp convertor though we do carry both we only use the latter about once a year.

As to running the coffee pot and the toaster simultaneously we plug them both into the same outlet and have never blown a breaker. Our coffee pot is only 600 watts and only draws sigbificant current for minutes while it brews. The toaster draws more current but again for only a couple of minutes.

We also have an in-closet air conditioner that draws about 5 amps.

When rewiring we carefully considered the assignments of circuits to breakers. Our goal was to assure that larger loads would typically be on circuits that are with typically low current or no current companions. For example our outside outlet is on the breaker that our electric heater is typically on.

The reality, at least in our trailer the only items that draw appriciable current, are the fridge and the electric heater.

In addition to our 10 AC outlets we have added 4 DC outlets.

The DC outlets, at least in our trailer are generally low current, used for our Endless Breeze fan and for running low wattage DC to AC convertors for our TV and Sat receiver.

We have no GFI breakers except on the house where the trailer plugs in. It came with none and we've added none.

[Cat futrell]

Hallelujah, I think I'm starting to get it. Let me just Make sure....If we have a 30 amp breaker box we can put four 20 amp sub breakers in, so that 20 amps will be available to each circuit. However if we exceed 20 amps on any breaker or 30 amps total (combined circuit usage) breakers will trip. The breaker maximums don't have to equal the 30 amp total, only the combined usage of all the circuits may not exceed 30 amps. And each circuit is limited to the breaker size.

There can be Five 20 amp breakers, each drawing 3 amps for a total of 15 amps which does not exceed the 30 amp main breaker or the individual 20 amp sub breakers. Is this correct?

[GPJ]

Yes, you have it (although you probably would choose a breaker smaller than 20A if your circuit is only drawing 3A).

And to be abundantly clear, lets change your example slightly...
There can be five circuits, each with a 20 amp breaker, each circuit actually drawing 5 amps (not exceeding the 20A breaker limit on each circuit) for a total of 25 amps which does not exceed the 30 amp main breaker.

[Cat futrell]

Thank you, thank you, thank you, to all. What a relief to be getting my brain around this. I am so grateful for all of the input and patience. I will inform the forum as we progress.

Cat

[Thomas G.]

Originally Posted by Cat futrell

Hallelujah, I think I'm starting to get it......

You have got it. Remember the breaker is sized to protect the wire from overheating, so the breaker size is chosen according to the gauge (size) of the wire conducting the electricity through the breaker.

[Cat futrell]

Sorry to be a bother.. Are there shallow outlet boxes ? Or outlet boxes with tabs that can be recessed in a wall with no studs?

[Cat futrell]

Got it Tom. I think we are using 12 gauge stranded wire. Shouldn't that support 10 amp breakers?

[Thomas G.]

Originally Posted by Cat futrell

Sorry to be a bother.. Are there shallow outlet boxes ? Or outlet boxes with tabs that can be recessed in a wall with no studs?

Yes, two basic kinds of boxes. One for new construction which generally attach to a stud and ones for retrofitting that grab the drywall (or whatever) around the box.

Originally Posted by Cat futrell

Got it Tom. I think we are using 12 gauge stranded wire. Shouldn't that support 10 amp breakers?

Yes, plenty robust.

[Cat futrell]

Is there supposed to be some sort of breaker or device that restricts the power coming in through the shore line? To prevent a surge from taking out our system?

[Thomas G.]

Originally Posted by Cat futrell

Is there supposed to be some sort of breaker or device that restricts the power coming in through the shore line? To prevent a surge from taking out our system?

There is a breaker that protects the outlet that you plug the trailer into (at the park or at your house). This breaker protects the extension cord if it is shorted.

This device is generally just a simple circuit breaker, and it does not prevent voltage surges. There are surge suppressors that do that and this has been discussed here several times.

http://www.fiberglassrv.com/forums/m...ppressor&sa=Go

[Joe MacDonald]

You should have a main breaker rated At whatever your power cord is rated for. Then each of your other breakers are fed from that one. In my Trillium I have a 15 amp main and my 6 circuits are also all 15amp breakers

[Joe MacDonald]

The reason for this is that if you used an adapter system to go from a 50 amp plug down to a 30 amp plug on your trailer the available current if something shorts out is more than what your cord is rated for. By adding the first breaker at what your cord is rated for the potential overload is avoided, or lowered to an acceptable (in my eyes) level

[Cat futrell]

Thanks Joe.

[honda03842]

Cat,

In most places I used plastic or metal electrical boxes. In the ends of the dinette I cut a hole and just installed an outlet, mounting the outlet with screws and than wrapped the screw area on the sides with electrical tape.



Attachment 63169

[Cat futrell]

Norm and Ginny,
How do you attach the box to the back side of the outlet?

[tda513]

as a first timer (1973 amerigo), i am sooooo excited to see the amazing amount of support that is offered by the members here! kudos to all including Cat for inquiring!

terina

[Thomas G.]

Originally Posted by Cat futrell

Norm and Ginny,
How do you attach the box to the back side of the outlet?

It appears that in this particular installation no box was used. Generally you want to have all 110 volt electrical connections inside a box.