Electrical question about amp rating: service entrance versus feeder

[teejk]

Uniform building code does not allow for facts...it's a "one size fits all" solution. I watched my foundation guys putting in drain tile on the footings inside and out of the footings (inside leading to a required sump pit with a pump). They were laughing since in our soil there will never be a drop of water in that pipe or sump pit and the pump will never turn on. Same for electrical code I think..."one size fits all" dictates the wire size that should be based on distance but isn't.

 

[PILOON]

I think Buikanddeere nailed it. Freeair!
If you were to run same amps in a conduit, sizes would change again.

 

[s219]

I think Buikanddeere nailed it. Freeair!
If you were to run same amps in a conduit, sizes would change again.

Nah, they have a different set of tables in the code for free air. All the tables I have been referencing are for conduit/raceway runs with up to three current carrying per group (above three and you have to start de-rating).

 

[teejk]

I think the temp rating on the wire comes into play. When I wired our new house all cables were rated at 90 and I guess I don't know how a piece of wire gets a 90 or an 80 or a 70. It was interesting though that I bundled all the down drops together to make it look nice but the inspector told me to cut them loose to permit free air flow around them. I've witnessed heat on 14ga extension cords before so I guess line-loss is more than what I thought it would be (i.e. back to the original topic...the 83% factor has to be related to the heat factor).

 

[s219]

And finally, I've done a few installs with that thick wire. Feed it into the conduit on the ground using LB's and dull tools...then use the conduit as a lever to bend it up to final position. You will learn some new swear words regardless of how you approach it.

Yeah, it's going to be interesting feeding three #1/0 (two hots and neutral) and one #2 (ground) through approx 100 feet of conduit. I have about 40 feet to run underground from generator to foundation, then 9 feet up an exterior wall, then 40 feet across an interior wall, then 6 feet down interior wall to panel, with a few turns here and there. See attached image, which is a top-down view from above. Trying to strategize the best way to do it, where to start, where to end, etc....

The underground and exterior conduits will be glued up ahead of time. For the interior, I may just friction fit the conduit together one at a time, sliding it over the wiring as I go. Though I have the option of running through a "raceway" for the interior portion, and I need to learn exactly what raceway means for residential code. Seen everything from cable trays, closets, and wall openings defined as raceways on the industrial side.

One strategy is to start at the halfway point and feed wire through the 9' vertical and 40' underground legs towards generator, before I swing the whole assembly up toward the exterior wall. In the process of doing that, I can start feeding the remaining cable through the wall into the interior and at the end swing the vertical up and affix the LB to the wall.

 

[hr3]

Just out of curiosity how far from the main panel are you running ???

 

[crazyal]

When I installed my service line, 350 mcm, I just laid the cable out and slid the conduit from each end. The hardest part was the elbow. I started there and slid the conduit from each side to it then kicked it into the hole. My not have bee how the pros do it but worked just fine. You do have to be a little careful as the edges on the conduit are sharp and will damage the wire. 40 feet should be easy. Mine was more than 200'.

 

[s219]

Just out of curiosity how far from the main panel are you running ???

About 100 feet total.

 

[CurlyDave]

... You do have to be a little careful as the edges on the conduit are sharp and will damage the wire. 40 feet should be easy. Mine was more than 200'.

Use a machinist's deburring tool on the ends of the conduit. The tool is under $10, the time is a few seconds per piece of conduit, and the wire will not be damaged.

 

[teejk]

Use a machinist's deburring tool on the ends of the conduit. The tool is under $10, the time is a few seconds per piece of conduit, and the wire will not be damaged.

I use a large drill bit in a cordless drill as a reamer when I play with metal conduit. Not so sure you need it on pvc.