Hello!
My wife and I are building our own small home in Florida using steel SIP construction. We have the shell done and are working out the details for the rough plumbing, electrical, and mechanical systems now. I'm stuck on figuring out the best way to bring power into the home and am open to suggestions.

Service is coming from underground and the meter will be mounted at the required 5'6"-6' height on one of the CMU columns. My plan was to use a 20 space combo meter/load center.

From there I would like to run Sch40 conduit up another 4-5' from the load center to a conduit body that will go through the wall just above the SIP floor panel. The floor will have 2x4 sleepers, then plywood, then finish floor, so the idea is to bring all of the indoor circuit wiring up through the conduit from the load center, through the wall, into the space below the subfloor created by the sleepers, where the circuits can be routed through the floor cavity or along the walls, which will have 3/4" furring strips with pine T&G boards.

The problem is after diving into the NEC, I'm finding issues with conduit fill capacity, derating for having over 9 conductors, using romex in an exterior conduit, and probably more.

Originally, I planned on just having a 200 amp disconnect next to the meter outside on the column, and running the required THHN type cables in conduit to a "sub panel" mounted in the utility closet. But the clear space code requirements aren't possible because of everything else we have to squeeze in the utility closet. Did I mention the home is only 600 square feet under air? There is only one interior wall with our studio layout and the only place the panel could be mounted in that wall is taken up by the pocket door.

Any thoughts? Thanks in advance! Here is a photo of our current state of progress:

 

I would consider mounting a panel on one of the columns under the house.

 

How would you bring the wiring for all of the circuits up into the house from the panel?

 

EMT conduit would be the best choice in that case. Run EMT and THHN to your first junction box on each circuit, then you can switch to romex for the remainder of the indoor circuit.

 

You could also feed UF cable from the panel to the first box.

 

I would consider a couple runs of 3/4" or 1" EMT or PVC conduit from the panel up to the house level. This will allow you to sleeve 3 or 4 NM-B cables in each conduit and not run afoul of derating. Do the math so you have 2 or 3 extras for future expansion.

For 15/20A circuits, you're allowed 9 current-carrying conductors in one conduit. So that allows four 14/2 or 12/2 cables (or a few more if you use MWBC).

 

Why is the house being built on columns? If the answer is because of frequent flooding there is no way I'd put the panel and meter socket on a column where they will regularly go under water. I'd put both panel and meter socket high enough that they will never get wet. I have seen many a river camp built with the meter socket abnormally high and the power company usually allows this variance from their normal service rules because of frequent high water levels.

 

I liked the idea of a single conduit to the house for a cleaner look and only one penetration to worry about sealing up, but multiple conduit runs may be the easiest solution. Thanks!

 

Yes, we are on the edge of a prairie wetland and the columns are required because of the flood plain, but I've only seen it flood once in the 35 years I've lived in the area. When FEMA updated the maps, they raised the 100 year BFE about 3' from where it was before and the columns are built much higher than the current FEMA requirement. The realistic 100 year flood elevation is only a foot or two above our slab on the ground so I'm not worried about mounting the meter 6' above grade. The thing about mounting the meter higher than 6' is that our PoCo requires permanent stairs and a landing built at our expense to access the meter.

The PoCo installed a transformer for underground service at the beginning of our driveway at ground level. When I asked their engineer about that being in the flood zone, he just said they would cut power to the transformer before the water level got that high. So even if the water gets high enough to reach the meter, the power will be cut long before that.