Electrical wiring question

[MattL]

Alright I need a bit of electrical help. I have an outbuilding/office at my house I want to wire for potentially 2 things. First I need to be able to provide power for a small a/c or small 1500 watt heater, lights, ceiling fan, laptop and TV. The second and not even certain that it will be needed but want to think for the future is the use of a small 120 welder series for the outside part of the garage-storage area. A/C, heater or welder will not be used at the same time.

The building is about 135 measured feet from inside breaker box. My service entry breaker box is a 125 amp. I currently have a sub panel off the service entrance panel/main to power my hot tub with double pull 60 (I think I have an option to drop it as low as 40 if needed, just eliminates one of the pumps)
Inside the house I have Stove @ double pull 50, Dryer @ double pull 30, Hot water heater @ double pull 30, Well @ double pull 20.

Judging from what I have read and understood I should be fine with a double pull 40 amp CB/240 supplying the power to via 8awg to the sub panel and drop it to the 120 from there a couple of 20 amp breakers via 12 awg.

I plan on putting power and network cables in separate conduits and burying them.

This leads me to the questions.
Question 1 what is allowable voltage drop that is per code 3% or 5% of source? I live in Tooele county. Per my calculations of 240/single 40 amp and 135 feet @ 5% I can run 8awg but it changes to 6awg if its 3% drop.

Question 2 how do I determine if I am overloading my main panel? I am pretty certain my inside one is a 200 amp.

Question 3 what would you run for wire 6 or 8 awg?

Question 4 suggestions on running network cable in same trench but elevate 6 inches in a conduit.

I have gotten some of the info from site 1, site 2

 

[MattL]

So ill ask another question,
4 would aluminum wiring be a viable option?

 

[jeeper]

Aluminum is a bad idea, it expands too much and shorts out. That's why we stopped using it.

 

[frieed]

Aluminum is just fine for a supply line to a sub panel and about 1/2 the cost of copper but
You will need a larger wire. I'd use copper on all the branch circuits.
Service entrance cable on most newer houses is Al due to cost, just make sure you use NoAlox paste on the connections to the panel and supply breaker.
The issues with Al wasn't just expansion, it also has a tendency to corrode when in contact with copper.
Newer outlets and breakers are rated for both (CU/ALR) marked on them somewhere.

 

[MattL]

Thanks! I understand about the aluminum to outlet boxes, I was just wondering about the run to the sub panel. I have copper runs to all outlets.

So any other thoughts on the other questions?

 

[gijohn40]

You can get number 6 wire to run from one panel to the other... if you are going to go aluminum then I would suggest #4 Your main breaker is rated at 125 amps? it must be an old house. I can't remember off the top of my head but you can go up to like 125-130 % of that 125 amp.

The trench pipes I assume are going to be PVC. so 6 inch of separation should be fine.

 

[MattL]

Thanks GIJohn40. The house was built in 82. There was a dig in last year and the service veendor replaced the old hardware with what is on the wall. I am in talks now as i think i got gipped.
Thanks for your advice.

 

[rambrush]

I would also throw a ground rod in that trench makes it a bunch easier than driving it south.

 

[MattL]

I would also throw a ground rod in that trench makes it a bunch easier than driving it south.

Thats a great idea. thank you

 

[gijohn40]

actually you are required to put two ground rods in at least 6 feet apart.