Are receptacles on mobile workbenches considered pendants?

[kolyur]

We need to have power available on some workbenches. The benches are on locking casters, so they are generally kept in the same locations but can be moved if necessary. The plan is to run SO cord from breaker, with proper strain reliefs, to a twist lock hanging over the bench. The mating plug will run to a 4sq box which is mounted to the side of the workbench.

Our safety manager is telling us that this is a pendant application, and as such the box needs to be a type with a hub so a strain relief can be threaded into it per 314.23(H)(1). I don't see a definition for "pendant" in the NEC but I have always assumed it to be a situation where some electrical assembly is supported solely by its attached cord. That is not the case here, as the workbench is providing the support (although not part of the structure which would disallow the use of cord). On the other hand, if someone gave the bench a push it could end up yanking the cord where it enters the box, which I suppose is the purpose of the beefier strain relief requirements for pendants.

Just wondering how others have interpreted this?

 

[hbiss]

We need to have power available on some workbenches. The benches are on locking casters, so they are generally kept in the same locations but can be moved if necessary. The plan is to run SO cord from breaker, with proper strain reliefs, to a twist lock hanging over the bench. The mating plug will run to a 4sq box which is mounted to the side of the workbench.

Yes, that would be a pendent. What you propose is good except that you cannot run SO cord from the breaker to a twist lock cord end above the bench.

What you want to do is use any chapter 3 wiring method such as MC or conduit on the ceiling to something like a 4 square box and suitable cover for a twist lock receptacle above the bench. Then you can drop down with SO cord with a twist lock plug and a Kellems or equal strain relief attached to the ceiling to your 4sq box below through a strain relief compression connector.

-Hal

 

[kolyur]

Thanks for the info. Can you point to a code reference that disallows flexible cord from entering a service panel to terminate in a OCPD? I see from 400.14 that the cord can run in a raceway up to 50 ft. So, what's the difference between it terminating in a 4x4 box and in a breaker panel?

 

[busman]

 

[hbiss]

I see from 400.14 that the cord can run in a raceway up to 50 ft.

Don't know where you get that from. Something new after 2017?

400.12 Uses Not Permitted.
Unless specifically permitted in 400.10, flexible cables, flexible cord sets, and power supply
cords shall not be used for the following:

(6) Where installed in raceways, except as otherwise permitted
in this Code

-Hal

 

[busman]

View attachment 2566565

This was from the 2014 book. Latest one I have electronically.

 

[kolyur]

Don't know where you get that from. Something new after 2017?

400.12 Uses Not Permitted.
Unless specifically permitted in 400.10, flexible cables, flexible cord sets, and power supply
cords shall not be used for the following:

(6) Where installed in raceways, except as otherwise permitted
in this Code

-Hal

It was 400.14 in my 2011 book. I see in the 2020 edition it has been moved to 400.17.

 

[hbiss]

One would argue that the allowance of flexible cords in such circumstances is for the connection of machinery.

Supplying ceiling pendants for receptacles however is clearly using flexible cordage in place of building wire.

Why do you have a problem with doing something the right way??

-Hal

 

[kolyur]

No problem at all with doing something the right way, I'm just trying to determine the right way(s) in this instance. I accept the fact that receptacles mounted to mobile workbenches constitute a pendant. So, we'll have SJOOW flexible cord with twist lock plugs, and the appropriate type of box mounted to the workbenches.

What I'm unclear about is the proper way to terminate the upstream ends of the cords. Yes they could hang with strain relief from a 4x4 box which would have conduit or some other Ch. 3 method back to the service panel. But how is that different from just running the cord a few extra feet to the panel and terminating it there directly? Does the prohibition against using cords "as a substitute for the fixed wiring of a structure" in 400.12(1) mean that cord can only be used in the specific areas where it could be flexing, i.e. the vertical drop from the ceiling to the workbench? This doesn't seem consistent with the exception in 400.17 which allows it to be run through a raceway for a limited distance.

I'm not trying to be argumentative, I just don't have much experience with cord applications and am looking for the specific codes that apply to this situation.

 

[Krusscher]

Where exactly is your panel? I am assuming it isn't in the ceiling so you are going to have SO cord just hang from the ceiling going to your panel? I think this might just be a case of "just because you can do it doesn't mean you should" I would at least stub up to a hoffman box in the ceiling and run your cords from there

 

[retirede]

No problem at all with doing something the right way, I'm just trying to determine the right way(s) in this instance. I accept the fact that receptacles mounted to mobile workbenches constitute a pendant. So, we'll have SJOOW flexible cord with twist lock plugs, and the appropriate type of box mounted to the workbenches.

What I'm unclear about is the proper way to terminate the upstream ends of the cords. Yes they could hang with strain relief from a 4x4 box which would have conduit or some other Ch. 3 method back to the service panel. But how is that different from just running the cord a few extra feet to the panel and terminating it there directly? Does the prohibition against using cords "as a substitute for the fixed wiring of a structure" in 400.12(1) mean that cord can only be used in the specific areas where it could be flexing, i.e. the vertical drop from the ceiling to the workbench? This doesn't seem consistent with the exception in 400.17 which allows it to be run through a raceway for a limited distance.

I'm not trying to be argumentative, I just don't have much experience with cord applications and am looking for the specific codes that apply to this situation.

The difference is that in order to run back to the panel, you would presumably have to attach the cord to the building, which is not permitted (see post 4). The 368.56(B) exception wouldn’t apply here.

 

[hbiss]

Does the prohibition against using cords "as a substitute for the fixed wiring of a structure" in 400.12(1) mean that cord can only be used in the specific areas where it could be flexing, i.e. the vertical drop from the ceiling to the workbench? This doesn't seem consistent with the exception in 400.17 which allows it to be run through a raceway for a limited distance.

Forget 400.17. Rarely will you see that happen, only place I remember that being done is with medical equipment, maybe some IT server rooms.

So, the rule of thumb is flexible cordage can only be used where it will not be attached or run through the building ceiling, walls, floors or doorways. Any place where normal building wiring could be used.

Basically, consider its use only for line cords and extension cords and you'll be OK.

-Hal

 

[Fred B]

No problem at all with doing something the right way, I'm just trying to determine the right way(s) in this instance. I accept the fact that receptacles mounted to mobile workbenches constitute a pendant. So, we'll have SJOOW flexible cord with twist lock plugs, and the appropriate type of box mounted to the workbenches.

What I'm unclear about is the proper way to terminate the upstream ends of the cords. Yes they could hang with strain relief from a 4x4 box which would have conduit or some other Ch. 3 method back to the service panel. But how is that different from just running the cord a few extra feet to the panel and terminating it there directly? Does the prohibition against using cords "as a substitute for the fixed wiring of a structure" in 400.12(1) mean that cord can only be used in the specific areas where it could be flexing, i.e. the vertical drop from the ceiling to the workbench? This doesn't seem consistent with the exception in 400.17 which allows it to be run through a raceway for a limited distance.

I'm not trying to be argumentative, I just don't have much experience with cord applications and am looking for the specific codes that apply to this situation.

Terminating directly into the panel board would clearly be "(1) As a substitute for the fixed wiring of a structure". Are you planning to have a cord end on both ends of cord that would allow it to get power from a typical receptacle? Then your use of 400.17 allowance might be allowed, but otherwise you would be trying to circumvent 200.12(1). IMO

 

[MTW]

I will share what I have used for years in industrial plants it not explicitly approved in the NEC for pendant drops but have installed hundreds of them over the years, and have never has a complaint from an AHJ or an OSHA inspector.

I use hardware and materials designed for drops to machinery from an overhead busway. You would be best to run it by your inspector before you put them up. But when done properly, I have never had an issue with an inspector or the plant personnel tearing them up causing a safety problem.

Start by installing a conduit from your panel up to the ceiling directly above where you need the pendant drop. Install a 4” box to the ceiling or truss. Use buss drop cable instead of rubber chords, buss drop is a bit tougher and has strength members built into the cable to resist pulling strain, and three bare ground conductors along with the insulated conductors, none of which use rubber insulation.

Use a box cover with a KO and install a wire mesh chord grip to prevent pull out and loosing of the splice connections. Leave a loop in the cable below the box to allow for a small amount of drop relocation and as an extra margin for error if someone ever hooks the drop and pulls down its support means. For the support use an eye bolt installed through the metal truss bottom chord, or screwed into wooden truss chord if that is what you have.

On that eye bolt, install a sky-ty bus drop support hanger with a spring that you order along with the sky-tyhanger. These are manufactured by Adalet if your wholesaler has never heard of them.

Make another generous loop of cable, about a 3’ diameter circle of cable and install it in the hanger, and tighten the hanging clamp securely.

From that hanger drop your bus drop cable down to your work station and install your outlet box on the end of the cable. Its best that you locate the box below the level of your workstation, so that when it is moved people do not walk aimlessly into the drop and crack their skull on it or poke their eyes out. When the workstations are removed, you can have a hook nerby where the drops can be moved to, to keep them out of harm’s way, until the workstation's have returned.

The box at the bottom of the drop should also have a wire mesh strain relief. The NEC has changed a few times over the years, requiring a box with a threade hub. A cast aluminum FS box meets this requirement but is heavier and stronger and more of a personnel danger when hanging out in the open.

I have used 4” square boxes as well when the NEC requirements were changed and have never had a problem with them either when used. The choice of materials and workmanship makes a world of difference. SJO chord strung up from the panel to the ceiling and back down to the workstation’s is just hackish to me and is clearly against the proabition of the code in using portable chord in place of permanent wiring methods.

 

[MTW]

Sky-Tie - Bus Drop Cable Clamp

www.adalet.com

A sheet metal beam clamp also makes a excellent hanger choice if you get the type that sprinkler fitters use, for hanging threaded rods for pipe supports. They have two holes in the bottom of them for the threaded ro to pass through, and they give you a good set of holes for you to hook the hanger spring securely in.

Robot or human?

 

[MTW]

 

[retirede]

I will share what I have used for years in industrial plants it not explicitly approved in the NEC for pendant drops but have installed hundreds of them over the years, and have never has a complaint from an AHJ or an OSHA inspector.

I use hardware and materials designed for drops to machinery from an overhead busway. You would be best to run it by your inspector before you put them up. But when done properly, I have never had an issue with an inspector or the plant personnel tearing them up causing a safety problem.

Start by installing a conduit from your panel up to the ceiling directly above where you need the pendant drop. Install a 4” box to the ceiling or truss. Use buss drop cable instead of rubber chords, buss drop is a bit tougher and has strength members built into the cable to resist pulling strain, and three bare ground conductors along with the insulated conductors, none of which use rubber insulation.

Use a box cover with a KO and install a wire mesh chord grip to prevent pull out and loosing of the splice connections. Leave a loop in the cable below the box to allow for a small amount of drop relocation and as an extra margin for error if someone ever hooks the drop and pulls down its support means. For the support use an eye bolt installed through the metal truss bottom chord, or screwed into wooden truss chord if that is what you have.

On that eye bolt, install a sky-ty bus drop support hanger with a spring that you order along with the sky-tyhanger. These are manufactured by Adalet if your wholesaler has never heard of them.

Make another generous loop of cable, about a 3’ diameter circle of cable and install it in the hanger, and tighten the hanging clamp securely.

From that hanger drop your bus drop cable down to your work station and install your outlet box on the end of the cable. Its best that you locate the box below the level of your workstation, so that when it is moved people do not walk aimlessly into the drop and crack their skull on it or poke their eyes out. When the workstations are removed, you can have a hook nerby where the drops can be moved to, to keep them out of harm’s way, until the workstation's have returned.

The box at the bottom of the drop should also have a wire mesh strain relief. The NEC has changed a few times over the years, requiring a box with a threade hub. A cast aluminum FS box meets this requirement but is heavier and stronger and more of a personnel danger when hanging out in the open.

I have used 4” square boxes as well when the NEC requirements were changed and have never had a problem with them either when used. The choice of materials and workmanship makes a world of difference. SJO chord strung up from the panel to the ceiling and back down to the workstation’s is just hackish to me and is clearly against the proabition of the code in using portable chord in place of permanent wiring methods.

Drops from a busway are specifically allowed by the aforementioned 368.56(B) exception, IMO.

 

[MTW]

Drops from a busway are specifically allowed by the aforementioned 368.56(B) exception, IMO.

But some will tell you that what I described is not from a busway, therefore not allowed. To each their own my feeling is a cable drop to a portable piece of equipment is safer than a pipe drop, by far. That’s why I used them for years. Bus or conduit run, never had a complaint or safety issue. It’s easier for the plant personnel to turn off a circuit at a panel-board, than to try and find the hook-stick that they lost years earlier.

 

[kolyur]

Thanks for everyone's replies. We ended up running TC cable overhead to 4x4 boxes above each workbench, then dropping the SJ cord from those directly down to each bench with Twist-Locks and strain relief.

I guess it was 400.17 that was throwing me for a loop since running cord in a raceway for up to 50 feet would seemingly open up lots of possibilities, but I see that most of these would end up being "a substitute for the fixed wiring of a structure" and thus in violation of 400.12.