Could a short piece of EMT be used as a sleeve to protect MC cable. A two foot piece protects the MC cable which then is terminated to a hot water heater. I was going to tell the Electrician to Re-do it, but I wanted to throw it out there for a Code Interpretation.
Thanks
If just a sleeve, then the way 300.15[C] is worded, it’s okay to do this with any cable type as long as there are fittings on the ends of the EMT to protect the cable from abrasion. I’ve used those plastic push-on bushings made by Arlington for that purpose before.
But, at least IMO, if actually changing wiring methods I feel that at least a changeover connector on the end of the EMT should be used as allowed in 300.15[F]. This may be up for debate though.
A little thinking on this:
What happens IF the EMT sleeve were to become energized? As I understand the OP, the EMT is basically 'floating', and therefore not bonded!
Just for my info, why would you protect MC cable into a hot water heater?
I agree. They should have ran the EMT to a junction box and then directly to the control box. The EMT is floating and I don't like it. Chances are the EMT will not get energized but ya can't tell the judge that.
Good Weekend
I'm with HOTLINE. Why a sleeve anyway?
u,If it is there BOND it.
I can imagine circumstances where you might want to sleeve a piece of MC; perhaps there's a particular section that might be subject to damage, or that you want to 'keep out of the way' and lack support points. Finally, theres the issue of penetrations, especially where you want to allow for future replacement of the cable.
Indeed, you would have to use a sleve if you had multiple cables to address.
I'm not worried at all about the sleeve becoming energized. Here's why:
First, we are not required 'structural metal that is unlikely to become energized.'
Second, there is the jacket of the MC, which is bonded. If the EMT is going to become energized, don't you think that the electricity is most likely to originate in that MC?
If you're a purist, you could assemble a fitting to make a direct MC -> EMT transition. If you're worried about abrasion, a connector or coupling on the ends of the EMT can address that concern.
300.10, exception,1 specifically allows "short sections" of raceway used as a sleeve for support or protection of cables to not be made electrically continuous.
I suppose it could be argued that "short sections" means raceways 24-inches or less, but not sure if that is an actual requirement.
Ah the old question "How long is short"?
I think I have 15 year old discussions from Prodigy about that spinning on a hard drive somewhere.
Harold E probably remembers some of them.
Before we wander to far from the OP....
Based on the OP, & how I envision what he described and IMHO, the wiring method perhaps should have been a raceway, not MC.
As to 'bonding' the EMT, it's not 'structural metal', it's a raceway. The short section is a gray area, as Greg said...define 'short'.
Again, IMHO a concern of phy. dam. to the MC? Terminate and go with a raceway.
What about dissimaliar metals? I would just use and EMT connector to a threaded half coupling to a M/C connector remove the sheath and install. I have done this in commercial building were M/C is run in the ceiling then surfaced mounted down the wall.
Ob
So if we're going to pick this to death, threaded half or even full couplings are not designed, manufactured or tested for joining connectors. Their purpose is solely for joining threaded conduits with tapered threads.
Yes we all do it and it will be done till the end of time, but that does not make it correct. That is why a fitting is made and more importantly tested to connect emt and rigid to flex and cable. In a similar way, threaded condulets are tapered to match threaded conduits, not emt or flex connectors which have no taper. But we still use them incorrectly all the time and will forever.
My point is that sometimes we do things in our trade which are not correct to the letter of the code or the UL listing, but so what? It is a big improvement over most of the worlds electrical wiring. How about European motor starters and circuit breakers that are over-rated and do not compare to Nema rated equipment. I could go on and on, but we are already bored! The sleeve provides more protection than no sleeve. The more complicated the code gets, the less likely that any of us know it all or comply.
What is the physical damage this MC may be exposed to?
I'ld be more worried about the water heater getting damaged in this environment.
Seems to be a whole lot about nothing here.
I’m not sure anyone is knit picking things here, especially NPT and NPSM or rigid fittings and their listed applications etc...
I will say though, that IMO, the installation the OP described is in compliance with the ’08 NEC as it is written in black and white.
The EC has met the requirements of the NEC regardless as to whether the inspector likes it on not... it is what I call, for lack of a better expression, a “shut up and sign” situation.
KJay, I agree, it was not long ago that a local inspector started requesting UL listed RX staples , as far as I know non were found.I think it just kinda went away.
Ob
OB:
Good point on dissimilar metals with al jacket MC and steel EMT.
Your method is an acceptable installation.
Dissimilar metals are always a concern. Key thing to remember is electrolysis needs a third component since there is no current present (at least there better not be) and that is an electrolyte. Without it you just have two types of metals doing its thing.
Different metals touching?
Let's get real. That same aluminum jacketed MC is routinely supported with galvanized steel clips, then connected to steel boxes with zinc connectors. Now we're worried about it touching a galvanised steel tube?
Other than the fact of MC/AC or RX Greg is right. We have had this discussion before. My thoughts then and now were, if the piece of conduit is less than 10' it could be used for protection from damage, once you start to go over the 10' mark, you might just as well run the conduit and be done with it.
If you were worried and dissimilar metals and if the metal conduit will become energized, then why don't you use PVC. It would protect the cable and not worry about the rest.
The longest "sleeves" I see are the ones that used to be mandated for RX running down outside block walls behind the sheetrock. Back in the olden days in Florida, they said the 1.25" was measured front to back from the drywall. Now they let it be horizontally from the furring strip and allow that to be a stacker. It was a bad decision in my opinion.
That only protects the cable from the sheetrock guy who knows where the wood is supposed to be. The homeowner, "probing" for the stud with a nail, is as likely to hit the wire as he is the stud.
The sleeves they put in were usually terminated with a EMT connector in the box and stapled where the RX came out so they were bonded. Occasionally, in newer work they had the EMT to RX connectors on top but usually the end was polished or they had a bushing on it.
I have seen them just dead end at the RX connector at the box and thus they weren't bonded. I thought that was sloppy work.
Just to join the chorus, I can think of two areas where one might routinely place a cable inside EMY for protection.
The first is the typical basement with exposed wiring. You're supposed to 'protect' the wires to a height of 6-1/2 ft, so cables run down to devices will often enter a pipe as they exit the ceiling level.
The second situation is where a cable passes through a 'classified' location. Often, the cable will be passed through a pipe, making the cable "outside" the classified location.
Regarding dissimilar metals... the only articles I can find in the NEC that actually reference it are below, so IMO, they would have no bearing on the OP’s installation.
110.14 Electrical Connections
342.14 Intermediate Metal Conduit
344.14 Rigid Metal Conduit