WTB 3 wire 4 gage copper "Romex"

[Jim Becker]

Aluminum is often used for this purpose, but it doest require a much larger conduit. The 200 amp feed to my shop building is aluminum and it was used because at the time it was installed, there was a "Significant" (with a capital S) cost differential between it and copper for these large conductors.

For coms and other low voltage conductors, the second conduit should be separated by about a foot from the power conduit (typically "less deep" if in the same trench)

[Mike Cutler]

Aluminum is often used for this purpose, but it doest require a much larger conduit. The 200 amp feed to my shop building is aluminum and it was used because at the time it was installed, there was a "Significant" (with a capital S) cost differential between it and copper for these large conductors.

For coms and other low voltage conductors, the second conduit should be separated by about a foot from the power conduit (typically "less deep" if in the same trench)

Jim
Here in CT, both conduits have to be at the same depth, 18" to top of conduit for PVC. They can both be in the same "trench", but the inspector will want to see a separation space between them.
It's interesting to note the variations in code compliance from different areas of the country.

[John K Jordan]

Put another conduit for low voltage in the same trench if allowed by local code.

I buried two additional runs of conduit along with the 2" run to my shop (250'). One is a 2" conduit with just a rope inside that I can use to pull something if needed in the future. The other is a smaller conduit with two ethernet cables, each rated for underground use. I use one for a WiFi router and the other is a spare. That conduit is on the other side of the wide trench from the electrical lines (almost 2' wide since I dug that one with my backhoe).

BTW, if there are any turns or curves in the conduit, rather than pulling a large cable or even individual heavy wires I think it's easier to lay the wire next to the trench and slide one 10' length of conduit at a time over the cable, then glue it to the last.

JKJ

[John K Jordan]

Why not use aluminum instead of copper?

I've heard stories about aluminum degrading underground but maybe that was with direct burial and perhaps poorly installed. I ran aluminum underground about 1000' to a barn site, sized to handle 80 amps because copper was more than I could afford at the time. It's been in the ground almost 10 years so far.

Warning: heavy cable is not easy to handle, although 100' should be easy. The hardest thing for my 1000' run was handling the huge reel of cable sideways on a slope and the length of a long field. Without rigging the tractor for unspooling it could have been a disaster with injury.

JKJ

[Tim M Tuttle]

Dedicated electrical suppliers sell wire significantly cheaper than Home Depot, and the larger wires can be bought by the foot. Some states require a license to buy in such stores. Some don't. Since you didn't list a location, I have no idea.

My supplier told me he can compete with HD on the larger wires but not something like 12/2 or 14/2 Romex.

I was actually shocked that the electrical supplier could beat HD on stuff like boxes, outlets, etc. I thought for sure HD would be the cheaper option. Pleasant surprise there.

[Julie Moriarty]

He referred to the wire as NM-B.

NM-B cable is not rated for direct burial. It's for dry locations, above ground only. USE or UF are commonly used for direct burial. The depth of the cable depends on local codes. 24" is usually a safe depth for direct burial cable. In the municipalities I worked, I've seen anywhere from 24" to 48" for direct burial cable. For PVC conduit, 24" was good most of the time. GRC can be as shallow as 12". When I was setting up cell site power feeds, one inspector required concrete encased GRC no less than 36" deep. So it's good to check with your local inspector first.

[Mike Cutler]

When I was setting up cell site power feeds, one inspector required concrete encased GRC no less than 36" deep.

WOW!
I hope all that site work was in the initial bid.

[Julie Moriarty]

WOW!
I hope all that site work was in the initial bid.

We were doing the work T&M but it was my job to keep the costs down. That one inspector wouldn't budge except on one site where we had to cut open the street to do concrete encased GRC. It was one of the main entrances to a big shopping mall. I "reminded" him of the POd mall goers inconvenienced by shutting down the street. He then relented and said we could directional bore under the street. "But it has to be GRC!" Some inspectors just have to remind you who is boss.

[Van Huskey]

I hate to say this but I think the OP might want to consult someone (at least his local inspector) more familiar with this type of work. I consider myself a decent attorney but don't have the expertise to handle an agency and partnership case.

The first issue is 3 wires to a detached garage. It should be 4 wires to get 240 into the detached garage. Romex is a tradename for NM-B and is not used buried even in conduit in any situation I am aware of. He might be loosely calling UF cable (which is different) Romex but then the OP mentioned NM-B.

I would personally use aluminum as long as it is handled and terminated correctly for the cost savings. If worst comes to worst there are wire suppliers on eBay that have decent prices for large cable if you choose something like SEU/SER/SE cable vs THHN.

My advice is talk to the local inspector but I think the OP needs some input from someone that handles this type of work regularly in his jurisdiction.

[Mike Cutler]

Van

I think he said that he SIL had a license, so I think it's just a lack of familiarity with the correct equipment nomenclature.

[Julie Moriarty]

Van

I think he said that he SIL had a license, so I think it's just a lack of familiarity with the correct equipment nomenclature.

Or maybe the OP didn't quote his SIL correctly. Anyone who has worked in the electrical trades past a couple of years should know direct buried cable is different than that used indoors and above ground. Knowing wire sizes and insulation types is pretty much 101 level.

[John K Jordan]

... Some inspectors just have to remind you who is boss.

That type of inspector seems common in agriculture. Some of those inspectors need to be reminded their job is to enforce the regs, not make them. I know of someone who pressed the inspector to show her the black and white while she had her own copy of the regs in hand. The local farm community cheered her. I have no idea how that would fly in the electrical business.

[Julie Moriarty]

That type of inspector seems common in agriculture. Some of those inspectors need to be reminded their job is to enforce the regs, not make them. I know of someone who pressed the inspector to show her the black and white while she had her own copy of the regs in hand. The local farm community cheered her. I have no idea how that would fly in the electrical business.

Remember the guy who liked concrete encased GRC? I went to the suburb next door to talk to the inspector about another cell site we were about to do. I told him we were planning to directional bore underneath the newly landscaped church property, so we wouldn't ruin it. He said, "What do they require in Schaumburg?" I told him concrete encased GRC. Then he said, "That's what I want." I wanted to ring his neck. Instead I told him I'd have to go to the pastor and tell him we have to tear up his freshly landscaped property. The inspector backed it down to directional boring GRC.

But for the most part, the majority of inspectors were very easy to deal with. Bring them in from the start and they will usually help you along.

[Tim Bridge]

NM-B cannot be run in any conduit underground or outside, it is a violation of the NEC 300.5(C) and 300.9.
These places are considered wet locations, and the inside of conduits are considered a wet location when installed underground or outside.
NM-B in rated for dry locations only.

[Tom M King]

When I built spec houses, I'd put "conduits" from the road to the house, so wires could be pulled in the future. I used black polyethylene, since it's available in long, continuous lengths. We'd suck a mason's line, tied to a little piece of cloth, though with a vacuum to pull wires with. I've had people come thank me 30 years later, that weren't even the people that I had sold the house to originally. Here, water lines only have to be a foot deep, so the conduits go in the trench under the water line.

Once phone contractor told me that they weren't supposed to put their wire in the same trench with anything else, so I started separating the conduits, with dirt, as they came out of the ground, and no one ever dug another trench. The little fake rocks serve as a number of covers on the lot corner at the road. No yards ever got disturbed.

When I built our barn, I did the same thing from the house to the barn. I didn't think to 3-way the barn lights to the house, but I had an easy way to get another conductor between the two. Later, we needed wires for cctv to the house to watch mares near foaling, as well as another lighting circuit with 25w blue bulbs in the mares stalls.

My recommendations for wiring in trenches between buildings, or from one place to another:

1. Dig the trench first, then measure how much wire you need, and get enough to make sure you have a few feet to throw away. Buy the wire first, and you're almost guaranteed to come up a foot short.

2. Any time you pull something through the conduit, pull another line with it for whatever you need it for next.

3. Take pictures that show where the trench is relative to the buildings, or better yet, put your path lights along one side of it. Put the pictures in that drawer in the kitchen. Some of the decades later thanks came because of those pictures.