I have a 250 ft run and I came across a 100 ft of 6/3. I want to run the 6/3 from temp pole to another box. Then use existing wire the rest of the way. What size breaker should I use at temp pole?

J,

It does not work that way. Temporary wiring is just that. It cannot be used as permanent wiring. Also, we need much more information from you.

For example, what is the Type of the cable? That gates how cable can be used. Does the cable have Copper or Aluminum conductors. At a hundred feet #6/3 AWG Copper can handle up to 60 Amps, depending on what it is connecting to. You need to know the temperature of the connection point to select the correct amperage. For example, 310.16 divides the temperature into 3 categories, 60c - 75c - 90c. The column you use is the column that gives the rating of what you are connecting to. That in turn gives you the max amperage you can supply via the cable.

Are you making an Overhead Connection or a Lateral connection (below ground)?

How about I just go with a 50 and call it good. And its being run underground. Oh and it copper

J,

That's part of the info we need.

For 6/3 AWG copper it is 55 Amp. (Using the 60c column) because you do not know the termination temp of the circuit, we have to use the 60c column.

Since we do not know what type of cable you have, I do not know if it can be buried, only certain types of cable can be direct buried or has to be used in conduit. Nor do I know if the cable can be put into conduit. This affects the depth of the required trench.

Can you give me something more to work with?

Obviously, if you were able to wire your Bat Cave you must be able to give us some more info. :)

It's a 6/3 wg type ufb copper wire. And I've had lights in the bat cave for 12 years now on a temp pole

J,

Is there a secret passage into the Bat Cave, one an electrical inspector cannot find. I am concerned about the use of a temporary pole. I mean, 12 years is an awful long time for a temporary situation.

As to the cable, South Wire markets a 6/3 UF-B cable. It is suited for direct-burial, which means that is needs to be covered over by at least 18" of top cover.

Since I have no idea what the connection temp rating of the device you are wiring up, it is necessary to use the 60c column.

Translated, that means that according to the NEC 2008, Chapter 3, article 310.16 the max amperage that can be used is 50 amps or a maximum of 40 Amps on a continious usage cable.

Continuous Load is rated at 125% of load. For example, a 32 amp continious load will be sized at 40 amps. 32A X 1.25 = 40A.

If you use the 50A load, then you would need to replace the entire cable with #4 AWG because the rating of the cable is exceeded.

50A X 1.25 = 62.5 Amps (rounded up to 63 Amps)

Thanks for all your help that should be good