THHN Wiring Question - Electrician Talk - Professional Electrical Contractors Forum

holyearth · 03-09-2009, 02:20 PM

The residential plans call for a 400 amp service with the following:

1) 3 Phase 4 Wire Main Disconnect Switch (SquareD) fused
2) 2 sets of 4/0 THHN 500 Feet

Now here's my questions:

1) Is SquareD the "best" brand? Would you put it in your own house? Does it matter?

2) Copper vs Aluminum wiring - no brainer - copper ...right?

3) The last question and the most confusing one ... I am shopping for wire and the distance between the electrical source and the house is about 500 feet. The plans call for "2 sets of 4/0 THHN" - but thats not rated for 400 amps I think 4/0 is rated at 260. Does 2 sets mean we combine the ampacity ratings? This is the part that confuses me. I was looking up the ampacities and basically I assumed I should be using a 500 MCM wire. Now that brings me to my next question. Since the plans call for 3 phase 4 wire, does that mean that the wire we end up using (whether its 4/0 or 500 mcm) needs to be 4 conductor? Or, do we get 4 single stranded wires? Cause, buying 4 runs of 500 ft 500 MCM copper will be VERY expensive :-(.

Thanks for your help!

Speedy Petey · 03-09-2009, 02:40 PM

Are you the homeowner or the electrician?

NolaTigaBait · 03-09-2009, 02:42 PM

square d is a quality product, id use it at my house, but i would be just as comfortable using siemens or murray...theres nothing wrong with using aluminum, as long as it properly terminated....4/0 aluminum is good for 200 amps 310.15b6....its run in paralell so two sets equals 400amps....are you an electrician?????

robnj772 · 03-09-2009, 02:46 PM

I think he should use 4 sets of 2/0
or maybe 8 sets of 1/0 yea,yea that stuff is lighter and can fit in the back of his station wagon

holyearth · 03-09-2009, 02:47 PM

I am studying to be an electrician and working alongside a licensed electrician. This is my first job working alongside a licensed pro. So, I am just trying to get a good grasp of things.

holyearth · 03-09-2009, 02:48 PM

I'll definitely recommend the SquareD ... what are your experiences with Cuttler-Hammer?

How's 2 sets of 3/0 or better yet 4/0? Definitely cheaper than 500 MCM

NolaTigaBait · 03-09-2009, 02:50 PM

Quote:

Originally Posted by holyearth

I am studying to be an electrician and working alongside a licensed electrician. This is my first job working alongside a licensed pro. So, I am just trying to get a good grasp of things.

i'd just run the 8 sets of 1/0

...if i were you

electricista · 03-09-2009, 04:33 PM

Quote:

Originally Posted by holyearth

3) The last question and the most confusing one ... I am shopping for wire and the distance between the electrical source and the house is about 500 feet. The plans call for "2 sets of 4/0 THHN" - but thats not rated for 400 amps I think 4/0 is rated at 260. Does 2 sets mean we combine the ampacity ratings? This is the part that confuses me. I was looking up the ampacities and basically I assumed I should be using a 500 MCM wire. Now that brings me to my next question. Since the plans call for 3 phase 4 wire, does that mean that the wire we end up using (whether its 4/0 or 500 mcm) needs to be 4 conductor? Or, do we get 4 single stranded wires? Cause, buying 4 runs of 500 ft 500 MCM copper will be VERY expensive :-(.

Thanks for your help!

A few question come to my mind. First is why are you shopping for the wire without your licensed person telling you what you need. Secondly, I am going to assume the cable in the ground is a wire that is run from the transformer to a meter on the house. Correct? or is there a meter and a main disco 500 feet away? There is a big difference here.

VD is something you need to look at if you run is 500 feet. What is the calculated load of the service? If your really want to supply a full 400 amps then 500 MCM won't get it.

Quote:

Originally Posted by NolaTigaBait

i'd just run the 8 sets of 1/0

...if i were you

8 sets? You are talking 32 wires? I don't get it or are you being facetious.