SER Cable In Underground Conduit

[Dennis Alwon]

Okay-- let's see if we can put this issue to rest. I have made an absolutely turn around from my first post where I said I did not see anything illegal. I have talked to the Southwire technicians who apparently has dealt with this issue for years.

He says there is nothing readable that is absolutely black or white on this issue but he says SE cable because of the bare conductor is not designed for underground in a conduit. If water gets into the conduit then the minerals in the soil will also be present in the water. Those minerals will eat away the bare aluminum conductors if the jacket is breached.

The jacket, as we all know, is not design to resist tear the way a UF cable will resist tear. If it does the wire will almost certainly fail.

If we as members of the forum accept the fact that aluminum in contact with soil conditions is dangerous then we need to not condone this installation. We can argue the code wording forever but why take the chance-- don't do it. I believe our standards should be higher than this and to assume some responsibility for a potentially dangerous situation when the code does not address an issue well. Play it Safe Silly (P.I.S.S. not K.I.S.S.)

 

[mpd]

dennis

I was at a seminar about 17 years ago and the guy teaching the seminar was warning all contractors about the potential problems using SER cable underground because of the bare aluminum equipment ground, it always stuck in my head.

are there any closing arguments from those who still think SE cable underground is not a violation

 

[George Stolz]

Here is post 100

are there any closing arguments from those who still think SE cable underground is not a violation

Are you trying to rain on our parade?

I will say this: I bet this discussion generates proposals to clarify the sections in question to remove all doubt. If anyone says there is no doubt, I would ask them to read the statement attributed to the former chair of the CMP overseeing the sections in question, who said there was indeed doubt.​

 

[bill@nkapc]

all of the s.e.r. cable i have seen have 3 insulated cond. of xhhw-2, and 1 uninsulated conductor, all aluminum. SER cable according to the UL white book list ser for wet locations only and aboveground. All materials used must comply with "Manuf spec. 110.3b.
Do not install ser cable underground unless the manuf. or a listing agent allow that cable for the specifics of that installation!
(Snip)
p.s. u can install xhhw-2 single conductors underground.
Bill

 

[david]

You are not going to get a listing for SE-R for direct burial or run in conduit
The alum alloy is the same material for both SE Type U and SE type R.

Most everyone would agree it would not be expectable to direct burial SE type R

I would suspect the sheathing could easily become damaged if directly berried and the Alum alloy (bare equipment ground) would not hold up very well to the corrosive conditions found in many soils.

And since conduits are not limited to PCV we still are allowed to run galvanized steel or protected metal conduits the outer sheathing of SER has not been listed to hold up to pulling through conduit. Yet we still can use conduit for physical protection of this wiring method . Every one here should agree we do not want alum to come into contact with steel in a wet location.

In a nut shell this is why I believe SER could not be listed for underground ground,

I do not believe SER presents any safety issue when installed in a PVC conduit underground. Since the alum is not terminating under ground I find it hard to believe the oxidation found on the outer part of the bare equipment ground would affect the ability of this conductor to clear a fault.

In the event there became a concern at a particular site the corrosiveness of the sub-grade conditions would adversely affect alum I would not approve it on a case by case decision.
In general I would approve the installation.

By the way, 10 years ago I first came across this I did fail one installation based on the fact that the cable was listed for above ground use. After a long discussion with the installer I reversed my decision this caused one day delay as I went to contact other inspectors with hair grayer then my own. The manufactured home is still up and running and the installer is still mad at me to this day, over that delay.

One other point the system of underwriters listing and labeling was set up to give authorities bases for approving, a comfort zoon if you will. The lack of listing or labeling leaves this burden on the installer to come up with a test that would satisfy the authority the installation is safe. I think that the lack of a listing or labeling of SER for use underground in and of itself is grounds for an inspector to reject the installation if he is not comfortable it is safe

 

[david]

For those of you who are ridiculing the inspectors who approve SER above ground and reject SER below ground

Just one other point of clarification there is a difference in a wet location under ground in conduit compared to a wet location above ground in conduit. Even if the under ground conduit is sealed tight. And the location is wet only due to condensation elimination the soil condition as my installer argued to win his case. The above ground conduit in a wet location can be and if we are talking service entrance cables are required to be, arrange to drain. So the cable in above ground installations should not get saturated in wate,r if proper weep holes are provided.

 

[brantmacga]

Particularly when "mobile home feeder cable" is cheaper, and contains an insulated EGC.

really? i pay $3.60 ft. for 4/0 SER and $4.22 ft. for 4/0 MH feeder.