How to ground messenger cable?

Status
Not open for further replies.
G

greenspark1

Senior Member
Location
New England
Hi. I have steel messenger cable that is supporting holiday lighting. Per NEC 396.60 this cable has to be grounded per 250.86. This means it has to be commented to the equipment ground. I don't see an easy/good way to do this since there won't be any junctions or terminations of the EGC anywhere near the messenger cable. I haven't used messenger cable before so sorry for the simple Q. The two options I see are:
  1. splice a pigtail into the EGC and connect to the cable. But I don't love the idea of adding a failure point on the EGC.
  2. find a nearby metal enclosure that I can run a #12 EGC to the messenger cable.

I'd also like to drive a ground rod just in case of any lightning activity. No Code requirement but reduces some risk of feeding lighting back into the building via the branch circuits.
 
greenspark1 said:
Hi. I have steel messenger cable that is supporting holiday lighting. Per NEC 396.60 this cable has to be grounded per 250.86. This means it has to be commented to the equipment ground. I don't see an easy/good way to do this since there won't be any junctions or terminations of the EGC anywhere near the messenger cable. I haven't used messenger cable before so sorry for the simple Q. The two options I see are:
  1. splice a pigtail into the EGC and connect to the cable. But I don't love the idea of adding a failure point on the EGC.
  2. find a nearby metal enclosure that I can run a #12 EGC to the messenger cable.

I'd also like to drive a ground rod just in case of any lightning activity. No Code requirement but reduces some risk of feeding lighting back into the building via the branch circuits.
Click to expand...

Do you just have a steel cable that you are attaching holiday lighting to?

If so it doesn't sound like messenger supported wiring as defined in 396.2

If outdoors, chances are the receptacle the lighting will be supplied from will require GFCI protection - I don't think it is that critical to have to ground whatever the holiday lighting is supported from - there is millions of sets of such lighting supported by metal rain gutters all over the place and most of them aren't grounded either.
 
kwired said:
Do you just have a steel cable that you are attaching holiday lighting to?
Click to expand...

Yes

kwired said:
If so it doesn't sound like messenger supported wiring as defined in 396.2
Click to expand...

396.2 definition is: (summarized) exposed messenger wiring supporting insulated conductors. Doesn't this match our install pretty exactly?

kwired said:
If outdoors, chances are the receptacle the lighting will be supplied from will require GFCI protection - I don't think it is that critical to have to ground whatever the holiday lighting is supported from - there is millions of sets of such lighting supported by metal rain gutters all over the place and most of them aren't grounded either.
Click to expand...

Yup, we're outdoors. Good point re: GFCI. I agree about rain gutters, but 396.2 talks about using a wire to support conductors. Not a metal rail or gutter.
 
greenspark1 said:
Yes



396.2 definition is: (summarized) exposed messenger wiring supporting insulated conductors. Doesn't this match our install pretty exactly?



Yup, we're outdoors. Good point re: GFCI. I agree about rain gutters, but 396.2 talks about using a wire to support conductors. Not a metal rail or gutter.
Click to expand...

You are not supporting NEC "conductors" you are supporting listed (hopefully) holiday lighting sets.
 
greenspark1 said:
396.2 definition is: (summarized) exposed messenger wiring supporting insulated conductors. Doesn't this match our install pretty exactly?
Click to expand...
Which of the 4 conditions apply?

I'm guessing "A messenger with a field-installed lashing material for conductor support".
 
kwired said:
You are not supporting NEC "conductors" you are supporting listed (hopefully) holiday lighting sets.
Click to expand...

Hmmmm, hadn't thought about it that way. So plug & cord connected lighting isn't a conductor. Maybe... but I don't see conductor defined as excluding listed wiring. The definition of "conductor, covered" seems pretty inclusive of any conductor with a covering.
 
greenspark1 said:
Hmmmm, hadn't thought about it that way. So plug & cord connected lighting isn't a conductor. Maybe... but I don't see conductor defined as excluding listed wiring. The definition of "conductor, covered" seems pretty inclusive of any conductor with a covering.
Click to expand...
Now throw in the fact that your holiday lighting is a multiconductor assembly, and is not an individual conductor or cable otherwise covered by NEC. It is utilization equipment that you decided to hang from a steel cable. It comes with it's own cord cap already installed on it, you just plug and play so to speak. If you were hanging a custom assembled lighting system of some sort from the steel cable, the chances of 396 applying to it might be greater, though it likely would need to be a listed system and you would also need to follow instructions included with listing as well.
 
IMHO the question you really need to ask is whether the support wire is likely to become energized, and decide on that basis whether it needs to be connected to the EGC.
If the lighting set is wrapped around the cable, I would say the latter is very likely to become energized. If the lighting set us suspended entirely below the cable using insulating clips, I would say it is not likely to become energized.

I would apply the same test when deciding whether metal roof gutters used to support holiday lighting need to be grounded.
 
GoldDigger said:
IMHO the question you really need to ask is whether the support wire is likely to become energized, and decide on that basis whether it needs to be connected to the EGC.
If the lighting set is wrapped around the cable, I would say the latter is very likely to become energized. If the lighting set us suspended entirely below the cable using insulating clips, I would say it is not likely to become energized.

I would apply the same test when deciding whether metal roof gutters used to support holiday lighting need to be grounded.
Click to expand...
FWIW, 396.60 does not use the "likely to become energized" qualifier.
 
Smart $ said:
FWIW, 396.60 does not use the "likely to become energized" qualifier.
Click to expand...

Good points by all, thanks for the input. It does feel strange not to ground a long metal wire that is in close proximity to energized conductors. But you're right about utilization equipment so it isn't actually required.
 
Messenger cable includes the support wire as part of the assembly imo. You have lights around a separate support wire. That it's acting as a messenger doesnt make it one.
 
Status
Not open for further replies.
Top