Aloha All,

I built a little 8'x12' office that is approximately 185ft from my main house. I was planning on running a electric, phone, and cable line in an underground conduit from my house to the office.
Can I just use 20A romex for the electrical line that will be tapped off an exterior outlet from my main house? If not, what type of electrical line would you recommend. BTW, the exterior outlet line has 2 other outlets on the same line on a 20A breaker, but the outlets are in a carport and rarely get used.
Also, can I run electric, phone, and cable line in the same conduit or will it create static?

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Originally Posted by bambuddah

Aloha All,

I built a little 8'x12' office that is approximately 185ft from my main house. I was planning on running a electric, phone, and cable line in an underground conduit from my house to the office.
Can I just use 20A romex for the electrical line that will be tapped off an exterior outlet from my main house? If not, what type of electrical line would you reccomend. BTW, the exterior outlet line has 2 other outlets on the same line on a 20A breaker, but the outlets are in a carport and rarely get used.
Also, can I run electric, phone, and cable line in the same conduit or will it create static?

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I forgot to mention the office will need electric for computer, phone/fax, lights, and possibly stereo, TV, and mini fridge.

No, power needs to be in a separate conduit, while all telephone, data, CATV, etc. in another conduit.

#12 is too small for that load and distance. #8 copper will give you 2.3% voltage drop for 40 amp load at 120 volts.

Thanks TKrussell, but sorry I am not knowledgeable regarding electric or know the lingo (that's why I am here). So what is it that your suggesting? What type of wire are you suggesting I buy or ask for at the store? What would you do? (ie. Get a #8 copper direct burial and run it off it own 40amp breaker)

You can use #8-3 with ground UF (Underground Feeder) cable, which can be direct buried, or install a 1-1/4" PVC Schedule 40 conduit, with 3#8 Cu and 1#10 Cu wires. This can feed a small two circuit breaker panel with two 20 amp circuits. Use one circuit for the electronics, and one for the lights and fridge.

Keep in mind that this is about the max load you can have with this run.

If you plan to add more space or more load in the future, then the electrical line should be larger, and now would be the time to install it.

Keep asking questions for what your not sure about.

If I get too technical, there are others here that can help with a different explanation. Also, there are some here that are good with tele/data lines.

Thanks again! But still unsure of a couple things. Originally I was going to run the office line off a 20A outlet in my carport. Can I still do this, or is it best to run the #8-3 with ground UF directly from from my main house's circuit panel to the two circuit breaker panel at the office that you suggested installing?

That's right you did say that. Yes,need to run a 40 amp circuit from the panel with my layout.

Thanks tk... it seems you gave me all the answers to do it the right way.

Now I don't want to offend your knowledge or experience, and I appreciate all your advice so far, but I like to run by you a less expensive alternative a general contractor friend of mine suggested. He said just plug into your one of my house outlets with a real heavy duty extension cord and run it through a conduit to the office and just put a surge protector on the office end.

The only reason I am even considering this is because it a fraction of the cost or the right way, but I like to know if there are any drawbacks or safety issues you see with this method?

Drawbacks are overheating the cable, low voltage at the end of the cable that will damage equipment, and cord is not to be used as a permanent wiring method, and not to be buried.

All I can say is try it.

That is why he is a General Contractor, not an Electrical Contractor. TK has Electric figured for you. I always sugest not only TV and Telephone, But Computer(as part of a network)Alarm sensors and keypad. It will let you know what is going on at house and protect office, innercomm, water, sprinkler line? You will be saving greatly by trenching and burying conduit yourself. Don't skimp on the wire or conduit, it doesn't get cheaper or easier than when the trench is open.