Ace's Wiring, Revisited

[DavidInWilmNC]

I'm in the same situation of needing to run 50 amp to my bus parking spot as Ace.  I was shocked at how much 6-3 UF cable is.  The 100 feet or so of what I need will be around $400 with tax from Lowe's.  I looked at 2-2-2-4 mobile home feeder, which is direct burial aluminum rated at 100 amps.  This is $1.82 per foot; about half the cost of the copper.  Of course, it'll be a bit more cumbersome to connect, but since it'll be going into a substantial breaker on one end and the bus bars on the other, it should be fine.  I'm probably going to use this with a 70 amp breaker in the main panel with a 50 amp 120/240 volt for the bus, a 20 amp 240 volt for my welder, and a couple 120 volt 20 amp 'convenience' outlets.  This seems to be the most economical way of running this cable, plus it should help avoid some of the drop associated with 'maxed out' AWG 6 over a large distance.  This cable also has a separate ground and neutral, so it should be fine for keeping the ground/neutral connection in one place - the main box.  Does anybody see any problems with doing this?

David

[Stan]

The main question is does the local inspector approve?

[Melbo]

Be sure to put the marker tape 12 inches above the cable which if I remember correctly should be 36 inches deep and protected ( even though the cable is UF ) to the 3 foot depth and then have an elbow so the wire won't kink at the bend.

I like to avoid inspectors as much as possible and go by the NEC

Melbo

[DavidInWilmNC]

The main question is does the local inspector approve?

I wasn't aware that this was going to be inspected.  I know of maybe one person with an outbuilding / detatched garage that had the wiring inspected.  That's not to say that it shouldn't. 

[belfert]

Be sure to put the marker tape 12 inches above the cable which if I remember correctly should be 36 inches deep and protected ( even though the cable is UF ) to the 3 foot depth and then have an elbow so the wire won't kink at the bend.

A UF cable is still vulnerable to cuts by shovel and such.  That is why the 3 foot depth.  Cable in conduit only has to be buried 18 inches IIRC.  I cheated on the conduit for my 30 amp RV post because the little trencher I rented would only go down about 12 inches.  (Did 30 amp as I only had a travel trailer at the time.)

I'm not sure if I will do a seperate service to my bus garage or not when I build it.  A big part of it is if a 100 amp subpanel will be big enough or not.  Another factor will be how much the electric utility charges for seperate hookup.

Brian Elfert

[Stan]

If it is not going to be inspected, then be sure that it meets all federal, state and county codes. It is not common to use service entrance cable between panel boxes, so there could be a lot of applicable rules. Usually this cable would come off a splitter box at the meter and the other end would feed a service entrance type of panel box. Assuming that you are coming off a residential style panel box, can you bend those #2 wires and put them into the connector on a 70 amp breaker? Is there a neutral lug that will take #2 wire? Are all you connection points cu/al or are they cu only? I won't even mention the risk of fire if aluminum conductors aren't terminated properly.

[Melbo]

Multi Strand aluminum is not the problem that single strand aluminum was ( which is no longer available ) and I don't believe that I have seen connectors for number 2 wire that were not rated al/cu that is not to say that they don't make them.

Also watch state and county codes as they can be way more restrictive than NEC.

Mostly concerning grounding and marking installations.

Melbo

[larryh]

Before you buy the Aluminun wire go to your recycle center you can usually buy good wire a heck of a lot cheaper I just picked up 4/0 two 50 ft pieces for 55.00 check em out.

LarryH

[DavidInWilmNC]

If it is not going to be inspected, then be sure that it meets all federal, state and county codes. It is not common to use service entrance cable between panel boxes, so there could be a lot of applicable rules. Usually this cable would come off a splitter box at the meter and the other end would feed a service entrance type of panel box. Assuming that you are coming off a residential style panel box, can you bend those #2 wires and put them into the connector on a 70 amp breaker? Is there a neutral lug that will take #2 wire? Are all you connection points cu/al or are they cu only? I won't even mention the risk of fire if aluminum conductors aren't terminated properly.

Yes, this is a huge outside panel right beside the meter with breakers for the inside panel, an exterior sub-panel, the A/C, and the detached garage panel.  The cable going to the inside panel is as large as the cable I mentioned and there is approx 6" of space between the connection part of the breaker and the side of the panel.  Being this is the main panel, there are several neutral lugs (4, I believe) that will handle this cable.  Also, being a main panel, the lugs are labled CU/AL, as are the Square D breakers in it.  This is how the service was set up before I bought the house... I guess the previous owners had 100 amp service in it and had the big exterior panel added to upgrade to 200 amp when they added central A/C and power to the garage.  It's been inspected, though it was around 17 years ago, and still has the the 'pass' sticker inside.  Now, if all I had was an interior main panel, I don't know that this would be the way to go.  It certainly depends on the particular situation.

David

[ArtGill]

David,
     I have used the "mobile Home service cable" that you are considering.  It is the proper size for 100 amps, so if you have a problem putting the wire in a breaker, just go to a 100 amp breaker, if you sub panel at your coach is rated for 100 amps or more.  Use "deox" on all Al connections.  As inexpensive as conduit is you may consider using conduit just to protect the wire. 

Art

[Stan]

David: That is a splitter box installation and should work out fine. I would put a 100 amp breaker  in the splitter and then use a 100 amp entrance panel at the other end. A small 24 circuit panel (12 1" breakers) would give you room for several 240 volt braekers plus some 120 volt circuits.  If you have a lot of space, you may have a visitor who would like to plug in also.

[DavidInWilmNC]

Stan, that's good to hear.  It'll sure make this easier.  This cable will enter my house's crawlspace and then make its way to the 'splitter box' outside.  Am I correct in assuming this will be ok as long as it's in appropriately sized conduit?  I believe that the cable has to be de-rated in ampacity when in conduit; is this also correct?  I'll definitely be renting a Ditch Witch type of thing, unless a construction friend of mine can borrow one.  Thanks.

David

[Stan]

David: I think you are correct in assuming that the splitter was an afterthought when the A/C was installed. Usually , a splitter box is just a junction box for all the building feeders tied to the main line coming off the meter without any circuit breakers. In other words, the cable going to a second building is basically a continuation of the cable coming from the utility company. The first breaker in then in a service entrance panel.

Direct burial cable should be protected at each end with a long sweep ninety into the ditch and conduit up to the box. If you are going to run conduit all the way, you would have to check the code books for the exact cable number and size of conduit to determine if you have to derate. Bear in mind that derating applies to continuous full load. If you had two all electric coaches plugged in running their A/C you would not come close to full load on #2.