Thread: receptacle outlet mounted in ceiling

Ken, Fred, Bill, (last names not needed, they know)

Question for you (and everyone else who wants to answer):

I just came back from our neighborhood Publix supermarket and noticed a cord hanging from the ceiling feeding a cooler on in front of the cashiers area where you enter from and noticed that it had a twist-lock plug and receptacle outlet, which go me to wondering ...

When a receptacle is mounted in the ceiling with the cord hanging down, is a twist-lock type plug and receptacle required?

Have not looked it up yet and was wondering what you thought about that type of installation (I'm going to look it up now).

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I can't answer the specifics, but that type of installation is pretty standard issue in many retail environments, meat cutting rooms for saws, etc.
Of course just because it is common does not mean it is right or wrong.
We see it every day with garage door operators with no twist lock.

Originally Posted by Jim Luttrall

We see it every day with garage door operators with no twist lock.

Good point, except that I would argue that a garage door opener is a static appliance and not likely to pull on the cord.

Originally Posted by Jim Luttrall

We see it every day with garage door operators with no twist lock.

That is precisely the receptacle outlet I was thinking about.

Originally Posted by Jim Luttrall

I can't answer the specifics, but that type of installation is pretty standard issue in many retail environments, meat cutting rooms for saws, etc.

Jim,

In looking through the UL White Book I have not yet found where ANY receptacle outlet is rated for, or approved for, "weight carrying" as in "carrying the weight of the cord" - not even for twist lock style receptacles.

Thus, all receptacles mounted face down would need to have the cord tied off with a strain relief to "something" up by the box (even the screw for the cover plate has no weight load carrying rating, so tying a strain relief off to that screw would also not be acceptable.

Unless I am missing something in the UL White Book.

There is no requirement to install a locking type receptacle in ceilings.

My thought is; an item that is plugged into a ceiling mounted receptacle and is not subject to abuse a strain relief would not be required. Such as garage door openers, neon signs in store windows and stores.
Items that are plugged into ceiling mounted receptacles and the cords are within reach (without the use of a ladder or stool) then the cord is subject to abuse and a strain relief should be used.
(Don't ask for a code article ,as these are my thoughts )

Originally Posted by ken horak

(Don't ask for a code article ,as these are my thoughts )

Ahhh, but ... "code" support (either way) is what I was looking for.

While the cord strain relief would not be allowed to be attached to the cover plate receptacle center screw, the box itself should well support that cord strain relief, so use a screw supporting the receptacle to the box.

As to your original question in your original post - No a locking receptacle is not required by the NEC. There is no code article to quote.

For the use of a strain relief how about:

2008 NEC Article 400 Flexible cords and Cables
400.10 Pull at joints and terminals
Flexible cords and cables shall be connected to devices and to fittings so that tension is not transmitted to joints or terminals
Makes for an argument for strain reliefs huh?

Tell me your not suggesting that someone use the receptacle mounting screw to attach a strain relief to.

Originally Posted by ken horak

As to your original question in your original post - No a locking receptacle is not required by the NEC. There is no code article to quote.

I could not find anything either.

For the use of a strain relief how about:

2008 NEC Article 400 Flexible cords and Cables
400.10 Pull at joints and terminals
Flexible cords and cables shall be connected to devices and to fittings so that tension is not transmitted to joints or terminals
Makes for an argument for strain reliefs huh?

Yes it does.

Tell me your not suggesting that someone use the receptacle mounting screw to attach a strain relief to.

No, because that would require modification of the listed cover plate to make the screw accessible, it was an example given to show why using the cover plate center screw *is not* a recommended attachment point - yet would be the most likely used attachment point for the strain relief.

I have written up cords and plugs for central vacuums and garage door openers before in the past when the receptacles were installed in the ceiling and seen that cord made me think about it again and bring it up here. Yes, at that time 'using the center screw of the cover plate' seemed like a good place for the strain relief, at least it was better than no strain relief - however, it really was not a proper place to attach the strain relief to. Shame on me for not thinking it through at those times - as I say, I am always learning something new.

I guess we have to define how tension relates to, and what joints and terminals are.

To me, joints and terminals refer to either a wire nutted connection or the back-stab/side plate/screw connector on the receptacle. The stuff in the slot is a blade contact and therefore isn't subject to the "tension" rule, at least that's my story.

Almost every vertically (wall) mounted receptacle supports a cord cap and a chunk of cord/cable when in use. This suggests "tension" if we insist on using the weight of the cap and cable/cord to say tension is applied to the ceiling receptacle "joints and terminals" by the weight of these items. I'm just somehow trying to rationalize how a cord, especially a short one, dangling from a ceiling receptacle needs a strain relief or some kind of hook for support when the five feet of cord on the fridge hangs with impunity.

The UL test for retention of the cord cap blades is a pull straight out from the receptacle face, much more like the ceiling mounted receptacle with a cord plugged in than the normal plug that is horizontal with "dangling cord" you usually see.

The NEC doesn't prohibit ceiling receptacles and indeed they are pretty much a fact of life in retail stores with displays and refrigeration equipment of various sorts. Absolutely none of my code books or specs or UL listings tell me hanging a cord by a cord cap from a ceiling receptacle is a violation of anything.

Absent a local code to the contrary I just don't see any code issues.

I have some what of a question about ceiling fans and just how they have been installed. most ceiling fans in older home have been installed by a standard box that is not approved for ceiling fans.

Best

Ron

Originally Posted by Ron Bibler

I have some what of a question about ceiling fans and just how they have been installed. most ceiling fans in older home have been installed by a standard box that is not approved for ceiling fans.

Ron,

That is specifically not allowed.

Those should be written up.

Next question: Newer house - how do you know IF the ceiling box is rated for ceiling fan use when you see a ceiling fan installed?

Answer: You don't.

That is why I always wrote up all ceiling fans as me not knowing whether or not the box supporting the ceiling fans are proper ceiling fan support rated boxes. I then recommended an electrical contractor verify the proper ceiling fan support box is installed, and, if not, install a proper ceiling fan support box.

Originally Posted by Bill Kriegh

I guess we have to define how tension relates to, and what joints and terminals are.

To me, joints and terminals refer to either a wire nutted connection or the back-stab/side plate/screw connector on the receptacle. The stuff in the slot is a blade contact and therefore isn't subject to the "tension" rule, at least that's my story.

Bill,

To clarify, then, where the plug blade is pushed into the receptacle slot and held in place by tension is NOT a "joint" by your thinking, right?

I have sent an e-mail off to UL asking them about the above question/discussion and will post their response here when I receive it.

Originally Posted by Jerry Peck

I have sent an e-mail off to UL asking them about the above question/discussion and will post their response here when I receive it.

Here is the short version of the response from a phone call from a UL engineer.

The regular grade off-the shelf at a Big Box store receptacle is tested, in its listing testing, to be able to support 3 pounds when mounted face down and a cord and plug is plugged into it.

His examples were:
- A short small cord, such as a lamp cord, weighs much less than 3 pounds and would therefore NOT require any type of strain relief. (Jerry's note: Like our example of a garage door opener cord, would not weigh much, no strain relief required.)
- A large cord, say #10 SO, say 10 feet long, would weigh in at well over 3 pounds and WOULD require a strain relief such as a hook in the structure or a support from the tile ceiling grid and then the cord would be swagged over and plugged in, with that part of the cord weighing much less than 3 pounds. (Jerry's note: Like my original example of the cord hanging down 10'-12' to a cooler, that would require a strain relief.)

A specification and hospital grade receptacle would be tested to hold a little more weight, he would have to do some research on that and let me know.

He will be doing some research and e-mailing me later with that information. I also asked about twist locking receptacle and if there would be any difference, he thinks no on that, but will check.

Added with edit:

Twist-lock type receptacles are not required to have a blade retention test and therefore have no stated weight carrying ability. The twist lock feature is to avoid accidental disconnection of the plug from the receptacle. The twist-lock feature for retention is mechanical and not tension of the blade contacts, there is no weight rating test of the mechanical structure to resist any weight, therefore there is no allowable weight rating for a twist-lock type receptacle.

I'm playing devil's advocate here since I don't like dangling cords anyway.

Jerry, the blurb about the twist-lock kinda goes back to my refrigerator cord issue. These cord caps HAVE to support a certain amount of weight if they are are used with a wall or ceiling receptacle. Is UL really saying that the twist-lock can't support ANY weight simply because they don't test for it? My experience with these basically is that the twist-lock will fail to support a long cable when small kids start swinging on it. Additionally, as with the refrigerator cord, there is the weight of a dangling cord on most receptacles in use. UL apparently doesn't test this for a maximum weight (straight out pull tested). Does that mean this is a forbidden use because of a listing issue? Although a vague term, is there an expectation of "reasonable use" by UL?

The "pull out" part of the test was added, I believe, back in the 80s due to the fact you could buy receptacles that wouldn't hold on to the cord cap at all. Since this is a "minimum" test that the 49¢ big box specials have to pass is UL saying this is the absolute limit? Or, do other grades have different limits? If so, then it is an issue that would seem to me to require some sort of permanent mark on the receptacle showing what is acceptable - many receptacles are sold bulk with no packaging. How would you know what the limit is after installation?

The question here appears to be are you violating the listing if your use goes beyond the minimum testing limits UL uses.

Originally Posted by Bill Kriegh

I'm playing devil's advocate here

I do that at times too, to stimulate the discussion as well.

Jerry, the blurb about the twist-lock kinda goes back to my refrigerator cord issue. These cord caps HAVE to support a certain amount of weight if they are are used with a wall or ceiling receptacle. Is UL really saying that the twist-lock can't support ANY weight simply because they don't test for it?

What UL is saying is that twist lock type receptacles are "not tested for retention of the plug blades". That means the twist lock type 'is not tested for retaining any weight on the plug'. That means there is no 'weight rating' in the listing and labeling.

The non-twist lock types "are tested for retention of the plug blades". That means the non-twist lock types 'is tested for retaining a specified weight on the plug'. That means there is a 'weight rating' in the listing and labeling.

The NEC, in "110.3(B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling." requires that listed or labeled equipment (and receptacles are required to be listed and labeled) "shall be installed and used" in accordance with their listing and labeling, which includes the standard to which they are listed and labeled to.

Thus, non-twist lock types have a tested and listed weight capacity of a minimum of 3 pounds. Hang more weight from the receptacle and you exceed that listing.

However, twist lock types have no tested and listed weight capacity. Hang more weight from the receptacle and you also exceed that listing.

This is was in the response from UL: "[FONT='Arial','sans-serif']It is stated by many who are responsible for interpreting the NEC that if not prohibited by the code then it is permitted. With that said, 110.3(B) requires listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling." The retention testing (or lack of) leads to the acceptable weight the receptacle is listed to support (or lack of).[/FONT]

My experience with these basically is that the twist-lock will fail to support a long cable when small kids start swinging on it.

As I recall from my conversation with the UL engineer, the strain reliefs built-in to the cord caps are tested to withstand a 15 pound pull. Thus, in addition to the receptacles limit there is the limited for the strain relief of the cord cap.

Additionally, as with the refrigerator cord, there is the weight of a dangling cord on most receptacles in use. UL apparently doesn't test this for a maximum weight (straight out pull tested). Does that mean this is a forbidden use because of a listing issue? Although a vague term, is there an expectation of "reasonable use" by UL?

What you are asking is like this:
- Let's presume that a certain structure is deigned, through testing and engineering, to withstand a 100 mph 3 second gust. At what wind speed with that structure fail?

- No one knows. That structure was not tested "to failure", it was only tested to "not fail" at 100 mph 3 second gust.

Same for those receptacles - they were tested to "not fail" at 3 pounds, and the cord caps were tested to "not fail" at 15 pounds.

At what point will they fail? No one knows, they were not tested "to failure".

The "pull out" part of the test was added, I believe, back in the 80s due to the fact you could buy receptacles that wouldn't hold on to the cord cap at all. Since this is a "minimum" test that the 49¢ big box specials have to pass is UL saying this is the absolute limit? Or, do other grades have different limits?

Specification grade and hospital grade receptacles are tested to those same tests and limits, with other additional tests done (but those particular tests are the same).

If so, then it is an issue that would seem to me to require some sort of permanent mark on the receptacle showing what is acceptable - many receptacles are sold bulk with no packaging. How would you know what the limit is after installation?

See above - they are tested to those same limits on those same tests.

The question here appears to be are you violating the listing if your use goes beyond the minimum testing limits UL uses.

Actually, the question is "Is the receptacle being installed and used in accordance with its listing and labeling", which includes the standard to which it is listed and labeled.

If the answer to that question is "No. It is being used in excess of it listing.", then that becomes a violation of 110.3(B).

The end result of the discussion should be "IF the receptacles are to be used to support cords of unknown weight, the listing should include that unknown weight and be tested for such." Of course, and ever so obvious, there would not be any way to test for "an unknown weight" and some weight limit would need to be chosen, agreed?

Currently that chosen weight is 3 pounds.

Let's suppose that the receptacles were, what to heck, tested for retention of ... 15 pounds to allow for the support of hanging cords (I selected 15 pounds as that is what the strain reliefs in the cord caps are rated for, make the entire assembly rated the same).

Okay, the receptacle MUST now retain the plug's prongs against a weight of 15 pounds ... and you thought it is hard to insert and remove a plug or tester now when only rated for 3 pounds?

Uh huh. Question skillfully sidestepped, but understandably so.

What we have here is a genuine problem. The fact is that a twist-lock can't be used without supporting some cord weight absent some support hardware - not required as part of installation instructions (and in itself may violate a listing). If they're saying 110.3(B) has to be enforced, and that twist-locks have no weight rating, we can't use them with a cord installed. Yet, I'm sure the twist-lock was tested with a cord installed. The cord cap will give a size range of different cable sizes allowed, yet the receptacle can't be used with any of this due to lack of a weight rating.

I think this shows a MAJOR problem with how things are listed, how listings are interpreted, and what overaggressive enforcement of listings can get into. (not questioning enforcement). So, do the code enforcement folks need to start visiting everybody with a scale in tow?

Another example is a pullbox with no knockouts. You have to make holes in it to use it, yet there is no info on how many holes (if any) UL used to test the box, where they were made, and whether using fewer or more holes in different places violates the listing.

You shouldn't have to call UL every time you put something into general use to see if it fits the listing, yet if you don't ............

Some of this may seem petty, but taken to the absolute letter of the NEC and UL listings, there are some gaping holes.

Originally Posted by Bill Kriegh

Uh huh. Question skillfully sidestepped, but understandably so.

Question not sidestepped, I thought I answered it.

So, do the code enforcement folks need to start visiting everybody with a scale in tow?

No, but they do need to be cognizant of the fact that receptacles have limited weight supporting abilities. Garage door opener cord and plug = does not weigh much. Heavy cord hanging from a high ceiling down to a refrigeration unit = does weigh a bunch.

All one would have to do is use their common sense and go 'Oh, that is a small lightweight cord, not a problem.', or, 'Oh, that is a large heavy and long cord and weigh quite a bit, problem'. It it then up to the contractor to bring out the scale and defend the weight if they so chose, or to install the 'Oh, yeah, this is just common sense.' strain relief to support the cord, leaving 'a small lightweight cord' hanging from the receptacle.

In as much as there are code problems with limitations, it is as much a problem with code enforcement officials and others trying to make fun of doing what is required instead of reading the code and going 'Oh, yeah, that makes sense, you can't hang a heavy weight from a receptacle without some type of strain relief.

It is people poking fun at the code which makes the code try to become more restrictive so you can't make fun of it, and that makes the code bulkier and more complex, so you try making fun of the code because it is more complex. If more people would apply common sense instead of trying to make fun of the code, the code would make sense to them ... after all ... the code is "MINIMUM" requirements, if you want "MAXIMUM" permissibility from a code, you will live to regret what you are asking for.

Here is an example which applies to those who try to make fun of the code and want to make it more complicated:

A cup of hot coffee is to be consider hot as it is a "cup of hot coffee". That is plain and simple common sense.

Those trying to make fun of the code need that cup of hot coffee to have a warning which says "HOT COFFEE - HOT COFFEE IS *HOT* - *HOT* COFFEE CAN CAUSE INJURY".

To all others, that is ... well ... just plain "common sense" - OF COURSE IT IS *HOT*, *I* ORDERED A CUP OF *HOT* COFFEE.

"Dangling plugs," or 'pendant receptacles' as they're more properly known, are a perfectly acceptable means of providing power where you need it.

There are various forms of strain relief, pf various ratings, and which method is proper is very much a design issue.

There is no requirement that there be a twist-lock type of device used, or that the bonnection be able to withxtand any particular load. Indeed, the local fire station has pendants specifically designed to realease the cords easily; they're used to provide 'shore power' to the trucks; it wouldn't do if a truck pulled out with a cord still connected!

Originally Posted by John Steinke

"Dangling plugs," or 'pendant receptacles' as they're more properly known, are a perfectly acceptable means of providing power where you need it.

Yep, and no one is saying that is not acceptable.

There are various forms of strain relief, pf various ratings, and which method is proper is very much a design issue.

Yep, THAT is the issue being discussed ... *the lack of* use of strain reliefs to support the weight of those cords.

There is no requirement that there be a twist-lock type of device used,

Also as stated above by others.

Sometimes we do agree.