1)Once USE has entered the building, is there a limit to how far it can run inside a wall without being in conduit? Code references appreciated.
2) How near to flowing water (as in a creek) can USE be run without further protection?
3) And speaking of creeks, I'm thinking of sleeving the USE in PVC where it runs over the culvert (because we might not get a full 18" below grade). So what does one use to seal the ends of a PVC sleeve in a situation like this? Is duct seal sufficient? And should I also use duct seal where the USE enters PVC to climb the exterior wall of the building it will be entering?
Thanks for your tolerance of my many questions. Only seven years in the trade, so it'll be "a while" before I've seen it all.
I'm not so sure you'll find all you answers in the code book. How far flammable conductors can go into a building is usually a local code issue. The length could be 0, a few feet, or maybe 10 feet and may require metalic conduit. If this is dual rated, then there may be no length limit, but you'll probably need to talk to the inspector.
Physical protection is also typically an inspector call.
PVC has to be buried 18", and USE would have to be 24". To go less than this requires rigid metal or concrete. If the culvert is a "driveway", you may have to go 24" regardless of how its protected.
You may not have to seal a conduit. USE is rated for direct burial, so it can get wet. You would have to seal the raceway if it was outside and entered a heated building since each end is exposed to different temperatures.
Mark Kent, WA
Re: more USE questions#97909 04/13/0612:20 PM04/13/0612:20 PM
Raider: thanks, but I already checked 338 before posting my questions. I didn't find my answers there, as Markp suggested I might not.
Markp: why a burial depth of 24"? I guess I should have specified that this is a single-family dwelling. Table 300.5 says 18", yes?
PCBelarge: thanks for the UL reference. In this case, the USE would be entering the building solely for the purpose of termination in a subpanel - probably less than 3' from where it enters the buiding. So it sounds like that might make it okay by UL. I just need to find out if it needs to be in conduit for those 2-3 feet.
Re: more USE questions#97911 04/13/0608:41 PM04/13/0608:41 PM
Table 300.5 is confusing. The most important item is row 1 column1 -- direct burial cable for all uses except the rows under it is 24". All of those other rows cover specific areas or coverings (buildings or concrete). I think the intent here is further protection and not less. Look at column 2 and you'll see RMC which is normally buried 6" has to be increased to 18" or 24" in most of those other rows. But if you're running this under a dwelling only driveway or parking area (perhaps even a gravel one), then you may be able to only go 18".
Mark Kent, WA
Re: more USE questions#97912 04/14/0607:16 PM04/14/0607:16 PM
Right, Bob - I, too, have noticed that that particular paragraph was eliminated from 2005. So no USE indoors - no matter how short a length, no matter if it is sleeved for that short a length? So what does that leave me with as an option? Maybe UF - but without my codebook in front of me at this moment, not sure. Let's see who finds that answer before me.