30A 220v instead of 50A 220v

[Timon]

Here is another option. You can run UF-B cable and you won't have to run a conduit except each end where you enter the ground until the run goes horizontal. The conduit entering the ground should be PVC and at least 1 1/4". For a 100' run you need #6. Here is an example. Check local code but it's normally buried 18-24" below finished grade. In freeze areas I'd run it below the freeze line.

Personally I still like conduit so you can add later but UF-B is 100% acceptable and commonly used.

[cb1000rider]

Originally Posted by FlyingDiver

You should be aware that running Romex in a conduit is against code as I understand it. Has to do with heat dissipation calculations. FYI.

I actually wasn't aware of it. Can you reference NEC on it?

I'm used to "Romex" being 12/2, 12/3, 14/2, etc - I thought it was a "brand" and not a wire type designation. There are areas where the NEC is clear as mud.

I understand what you're saying, but if you look at the head capacities / specs though, type NMB (Romex) and THHN have the same temperature ratings. NEC allows THHN in conduit. So this doesn't make sense to me.

NEC does allow Romex in conduit for "physical protection" - this is usually a transition as I understand it.

Additional understanding is that NMB Romex IS allowed in conduit, subject to appropriate space in that conduit. Honestly, I have run 12/2 romex in conduit before, but I use 3/4 conduit. The size is conduit size is overkill.

Think about it another way: My home has foam insulation. I've got 12/2 romex running all over the walls. I promise that the foam holds heat much better than a 3/4" piece of conduit does. Not terribly "safety" concerned, but if someone can site NEC on why it's a violation, I'll take it into consideration.


Timon, I'm aware of UF-B cable and that's a great suggestion. However, where I live, it's substantially rocky. Literally you've got to bring in a rock saw to trench. My neighbor has UF-B in his yard and it's been a reliability disaster. I'd rather do runs of conduit...

[FlyingDiver]

I'm not an electrician, I just remember one mentioning it to me once. Now that I think about it some more, I think it's multiple runs or over a certain size is not allowed. And by Romex I mean the jacketed two or three conductor (plus ground) commonly used. For large gauge wires, or multiple circuits (more than three conductors), I think individual wires THHN is used.

Hmm. Now that I think about it some more, I'm sure jacketed is allowed for single circuits (at least), since the wires going to the floor outlets (conduit in the slab) is jacketed. But it's burial rated, not the normal wall stuff, since those conduits can get water in them.

[CJ7ole]

Running jacked cable in a conduit recently came up in another forum. A retired Chicago electrician (very well respected on the forum) said she (yes, she!) would never run jacketed cable in a conduit and didn't know any other electricians that would either. I will admit I have done it for short distances instead of adding a JB to change wire types. For example going into a 4' section of conduit dropped from the joist space on a concrete basement wall servicing a 30 amp 220 volt dryer outlet.

[cb1000rider]

I'd ask her:
1) If it's a code violation, cite the NEC.
2) Why? (Logically)

And look, I'm an follow-the-rules guy, but cased wires do much better where I am. I'd never run that ground contact stuff. I understand I can do unjacketed wire, but the only reason I've heard that it might be an issue is that the jacket + conduit can't exchange the heat. That just doesn't make sense if it's allowed with modern foam insulation in homes.

[MattC]

CB,

If you ever said how far you were going, I didn't find it.

Do yourself a favor right now....
Can you run a speadsheet??
Cost the job. Copper can be expensive (it is actually pretty good right now), but labor is almost always more. If the labor will be yours, it still isn't cheap. When you think you are done, go and get real quotes on the cables you are considering. LoweDepot might be best (if you don't have a card), but call everybody you can find.

Next, You say it is rocky there and a neighbor has had trouble with buried UF?
Take a lesson. Buried cables are always a Son of a Bear.
I haven't read NEC or even NEMA recently, but direct burial cable needs to be 18" down. If it is rocky that can be a long way - even for a DitchWitch. Hard conduit does not have to be buried at all. Wire in conduit doesn't need a GFI at the source. And, It won't get screwed up by the bozo landscaper that wants to plant a cactus there.

Am I an electrician? Not any more, but I am a EE and worked as a ships electrician before I came ashore. I kept working the card until I got the I better one.

If you are smart, you will bury two pipes. One for the AC, and the other for the cable TV, Internet and telephone (and maybe even water later).

Roll that into your spread sheet, you will find the the second pipe is almost free. By now, you may have figured out the the copper cost is just not all that big.

Again, If you bury conduit and pull cable and it doesn't work out at 30 amp, you can pull that copper out and upsize it.

I am going to drop this here, but if you have a question about the above, send me a private message.

Good Luck Guy.

Matt

[Timon]

Originally Posted by cb1000rider

Timon, I'm aware of UF-B cable and that's a great suggestion. However, where I live, it's substantially rocky. Literally you've got to bring in a rock saw to trench. My neighbor has UF-B in his yard and it's been a reliability disaster. I'd rather do runs of conduit...

Yea, that makes it a royal PITA. I've seen it done without problems but you have to do so much prepping of the hole that it's not worth the time and effort. It's cheaper to just run PVC conduit. While your at it run another conduit, higher in the hole, and run things like phone cable or the like. You may not need it in your case but it can be useful.

[CJ7ole]

Sorry, I am out of town for another week and my NEC book is in the shop so I can't provide my own provide citations. Basically NM jacketed cable is not rated for below ground service, in or out of conduit, because it is not rated for areas subject to moisture. Conduit below ground will get water into it sooner or later.

From another source: "You cannot use nonmetallic sheathed cable (Type NM, NMS) in conduit in any damp, or wet location (NEC 2011 300.5(B), 300.9, 334.12(B)(4)). Instead, you'll want to use individual conductors rated for wet/damp locations"

Also from the same source: "National Electrical Code 2011

ARTICLE 310 Conductors for General Wiring

II. Installation

310.10 Uses Permitted. These conductors shall be permitted for use in any of the wiring methods recognized in Chapter 3 and as specified in their respective tables or as permitted elsewhere in this Code.
C) Wet Locations. Insulated conductors and cables used in wet locations shall comply with one of the following:
(1) Be moisture-impervious metal-sheathed
(2) Be types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THWN, THWN-2, XHHW, XHHW-2, ZW
(3) Be of a type listed for use in wet locations"

I cannot verify these citations though.

At Home Depot:
#6-3 With Ground UF solid strand, 125' coil, $309 underground jacketed feeder cable
#6 stranded, 500' spool $180, THHN, likely a bit more for moisture rated
#8 stranded, 500' spool $120, THHN, likely a bit more for moisture rated

Practically, why pull 4 stranded wires vs 4 solid wire jacketed cable? Much easier to pull and cheaper.

[cb1000rider]

Originally Posted by MattC

CB,
If you ever said how far you were going, I didn't find it.

I haven't said, I've got two install options. Lengths differ greatly. I understand wire length (span) tables and how length affects gauge of wire.

Originally Posted by MattC

Can you run a speadsheet??

I sure hope so. :-)

Originally Posted by MattC

Take a lesson. Buried cables are always a Son of a Bear.
I haven't read NEC or even NEMA recently, but direct burial cable needs to be 18" down. If it is rocky that can be a long way - even for a DitchWitch. Hard conduit does not have to be buried at all. Wire in conduit doesn't need a GFI at the source. And, It won't get screwed up by the bozo landscaper that wants to plant a cactus there.

FYI - a ditch witch won't cut it here. I've tried. Literally you need a "rock saw". Lots of limestone. Lot was scraped originally for road base.

I'm aware that once the trench is there that I should maximize the use. However, we don't do wired telephones anymore and don't use satellite service. Both are provided over internet and a big WIFI network. Likely will run water though.


I'll consider what you guys are saying - that it's easier and probably more code correct to pull non-romex. I want to stay out of pulling single wires, of course.

I've done bigger stuff for the shop (I put it in) - 1" conduit, 6 gauge wire, 50A service for a shop non-cased. I'll admit to using 12ga Romex for some small stuff (through conduit) - but it's what I had on hand and didn't pick up that it might be against code.

Like you, I'm an EE that has some some residential wiring (that's passed code). That doesn't make me a know-it-all and I find that it's good to ask the practical questions, so I can learn before making a mistake...


Re-pulling conduit, especially anything over 50' with more than a single bend is a real bear, even in smaller sizes. I avoid it if at all possible.


Thanks for your input, Matt.


CJ7ole - Thanks for your citations, that's what I was after and didn't pick those up on my own. I understand the basis... Appreciate the lookup.

In terms of source, Home Depot and Lowes are much more expensive than a quasi-local electrical supply house.

[CJ7ole]

I gave HD pricing just to demonstrate pulling individual wires is less costly than a bundled cable. I am not clear on your aversion to pulling a bundle of 4 proper wires vs a jacketed cable.

[wa8yxm]

Originally Posted by cb1000rider

I'm used to "Romex" being 12/2, 12/3, 14/2, etc - I thought it was a "brand" and not a wire type designation. There are areas where the NEC is clear as mud.
...

You know what a Band-Aid is right? Well most people will give you an answer that is technically wrong if you ask them.

The "Generic" name is self adhesive bandage. Band-Aid is a brand name of a self adhesive bandage.

Same with Romex. Like Band-Aid it's used to describe a type of wire cable... It is also a brand name.

Unlike band-aid, I do not know the proper generic name since it does not matter.. I just call it Romex.

(the only reason I know the Generic for Band Aid is Michigan State Police First Aid kits,,you see that's what we had in the office (Dispatch center) and the box said 1x3 Self Adhesive Bandage.. Nobody could find the Band-Aids box in the kit.. So they trained us on it.. I kid you not).

[predawn]

Originally Posted by cb1000rider

So, thinking about putting up an RV space on property at home. Running 50A of 220v is a bit of a pain - it requires 4 conductor 6 gauge wire, which is a pain to deal with, especially when you're doing runs in conduit.

I'm thinking of doing a 30A 220V circuit instead, but don't know if that actually makes sense. As long as RV manufacturers are putting ACs on separate "legs" it should work great, allow use of 10 gauge wire and make it a lot easier to install.

Obviously we put a 50A 220V plug on it - not a standard "30A service" and put it on a 2-pole 30A breaker.

Someone tell me that this is a dumb idea....

u could use #8 and make it 50 amp it all depends on the run length
or u could use 2 wire #6.use the copper as your neutral and the conduit as ground.Iam not sayings up to code but I know for fact it works fine

[Timon]

Originally Posted by predawn

u could use #8 and make it 50 amp it all depends on the run length
or u could use 2 wire #6.use the copper as your neutral and the conduit as ground.Iam not sayings up to code but I know for fact it works fine

You don't want to use metal conduit underground, you use PVC and run a ground wire. On a 50A circuit you can use a #8 ground with #6 for the two power and neutral wires figuring a 100' run.

[cb1000rider]

Thanks for all the discussion guys. Here's the plan:

• rock saw the trench
• pull a length of #8 copper cables ~100 ft, 4 of them
• encase in 3/4" gray PVC conduit
• 30A double-pole breaker on the break box
• Run into a standard 50A RV-style outlet (outdoor, wet use), labelled "30 A limit".

Should run 2 ACs + no problem.

I appreciate the discussion and suggestions.