Improper Use of Fittings

[jack horner]

That is the best way to make this connection. Anyone who has every installed this would agree that the use of these fittings verses use an EMT to flex connector is far better.

 

[jack horner]

IAEI UL Question Corner

http://www.iaei.org/subscriber/magazine/06_c/2006_may_questioncorner.pdf

See the second question, it is getting close to this subject with some similar issues.

Q A common practice I see in
the field is EMT offset connectors
screwed into hubs
on outdoor enclosures. Are
EMT offset connectors or any EMT
connectors or fittings Listed for use
with threaded hubs, such as on a conduit
body or Myers hub?

A All hubs are intended for
use with threaded conduit,
not fittings. Hubs are provided
with a tapered thread, and
so is threaded conduit such as rigid
metal conduit or intermediate metal
conduit (IMC). EMT fittings have
a straight thread and are designed
for use with a lock nut, intended
to secure to an enclosure through a
knock out or punched hole.
When the straight thread of the
connector or fitting enters a hub in a
wet location, the wet location rating
may no longer be valid because the
wet location rating of the hub depends
on the tapered thread engagement
of the tapered conduit thread
into the tapered thread of the hub.
With a straight threaded connector,
the thread of the connector never
locks into the tapered thread of the
hub, therefore not providing a seal
to keep out moisture.
An EMT fitting marked for use
in a wet location is provided with
or is used with a gasket between the
fitting and the hub. When the fitting
is tightened the gasket can be
squeezed out from between the fitting
and hub and may not provide a
means to keep out moisture.​

Other considerations with straight
threaded connectors into a tapered
threaded hub may be grounding.
Depending on the installation of the
straight threaded connector into the
hub, the contact may not be tight
enough to assure an effective groundfault
current path. The connection of
straight threaded connectors, such as
EMT connectors, is not evaluated
with hubs as part of their Listing.
Hubs are Listed under the product
category Conduit Fittings (DWTT).
EMT fittings are Listed under the
product category Electrical Metallic
Tubing Fittings (FKAV). The Guide
Information for DWTT can be located
on page 22 in the White Book
and FKAV on page 33 or online by
entering DWTT or FKAV at the
Category Code search on UL?s Online
Certification Directory located
at www.ul.com/database​

Joe, Rigid conduit couplings like the one shown in the picture are NOT tapered so this would not apply.

 

[e150club]

the weak link is those squeeze connectors after a couple of years of the flex getting stepped on and knocked around broomes ect ect... the flex falls out or the flex gets streched into a slinky. they dont give any strain releif.

 

[tallgirl]

the weak link is those squeeze connectors after a couple of years of the flex getting stepped on and knocked around broomes ect ect... the flex falls out or the flex gets streched into a slinky. they dont give any strain releif.

Sounds like you've been hanging around raised floor computer rooms a lot.

 

[iwire]

the weak link is those squeeze connectors after a couple of years of the flex getting stepped on and knocked around broomes ect ect... the flex falls out or the flex gets streched into a slinky. they dont give any strain releif.

That sounds more about improper supports than anything else.

Flex is almost always required to be secured to the structure.

 

[tallgirl]

That sounds more about improper supports than anything else.

Flex is almost always required to be secured to the structure.

When you build data centers, how do you provide power to the location where the equipment is going to be positioned? Are all your receptacles rigidly mounted on posts, the floor, something else? Or are they on the ends of some length of flex?

I assume you've built at least one raised floor room and I can't imagine the ends of the cables secured to much of anything as one advantage of raised floor rooms is the ability to move everything to wherever you want it, as well as reconfigure what sort of power is provided where without having to get an electrician involved.

 

[roger]

When you build data centers, how do you provide power to the location where the equipment is going to be positioned? Are all your receptacles rigidly mounted on posts, the floor, something else? Or are they on the ends of some length of flex?

I assume you've built at least one raised floor room and I can't imagine the ends of the cables secured to much of anything as one advantage of raised floor rooms is the ability to move everything to wherever you want it, as well as reconfigure what sort of power is provided where without having to get an electrician involved.

Julie, there is no exception to the requirement of securing and supporting the feild installed wiring under raised floors.

See 645.5(D)(2), don't confuse the allowance in 645.5(E) which is dealing with cords, receptacles, cables and such that are part of the listed equipment, Field installed wiring which is the flex, sealtight, or what have you must be installed in compliance with 300.11.

Roger

 

[wanderer20001us]

I agree with Roger. That is a very common misconception of 645.

 

[iwire]

Are all your receptacles rigidly mounted on posts, the floor, something else? Or are they on the ends of some length of flex?

If I install it they are rigidly secured, the NEC requires it.

Even under a raised floor pipe, flex, MC cable all must be secured and the boxes they terminate into must also be secured. I usually Tek-screw the boxes to the floor legs.

Unless they are manufactured and listed whip assemblies. If they are listed whips they do not have to be secured. Any that I have handled have been made of Liquidtight Flexible metal conduit.

Usually they are pretty tough but I have seen them broken from severe mishandling by the unexperienced. The breaks happen when some tries to pull a 'curly cue' (we use another name I can not say here) out of the flex from the end instead of walking back and doing it hands on.

I assume you've built at least one raised floor room

No but I saw one on TV.

Actually Peter D and I just recently ran a new 1600 amp 480 feeder to one.

Just waiting now to rewire the entire room.

 

[tallgirl]

Unless they are manufactured and listed whip assemblies. If they are listed whips they do not have to be secured. Any that I have handled have been made of Liquidtight Flexible metal conduit.

The ones I see most of the time look like someone made them there on the spot. On the other hand, I don't install them, I just use them

Usually they are pretty tough but I have seen them broken from severe mishandling by the unexperienced. The breaks happen when some tries to pull a 'curly cue' (we use another name I can not say here) out of the flex from the end instead of walking back and doing it hands on.

Never underestimate how much abuse the experienced can inflict on whips. People get highly impatient and drag whips hither and yon, clunking them over everything in between. And if impatient doesn't work, "lazy" is more than sufficient to make up the difference. It takes a special kind of experience to do that.

 

[e150club]

i did industrial wiring long manufacturing machines and printing equip.we did also wire the comp. room. the long mach. mostley had 4" throughts that ran the length of the machine. flex out the top to motors,heaters,control stations & panels ect. it was like spagetti on some machines. and the flex got the crap beat out of it. some even got hit by forklifts as did my tool box once.

 

[Johnmcca]

It seems to me, and correct me if I'm mistaken, that Joe's real problem with this fitting assortment is the ground fault return path. If that is the case, Joe, write a proposal for the inclusion of a properly sized EGC anytime a FMC, or LTFMC is to be used, or a properly sized jumper across the flex. That would end it, forget the tapered vs. straight thread argument, or the set screw argument. Jump it!

 

[don_resqcapt19]

John,

It seems to me, and correct me if I'm mistaken, that Joe's real problem with this fitting assortment is the ground fault return path.

That shouldn't really be the issue because flexible metal conduit is only suitable for use as an equipmemt grounding conductor when the conductors in the conduit are protected by an OCPD with a rating of 20 amps or less. The conduit in the picture looks like it is bigger that what would be required for a 20 amp circuit, so an alternate bonding path is already required by the code.
Don

 

[Tori]

oh oh , I have done this many times though without the lock nut - that makes it look crappy - The threads do indeed match and you can screw them together very tightly and they are better then what I have seen made for this application

Do you mean you worked under specs that do not require you to pull a grnd wire ? I was beginning to think it was a standard

would the alternative be a 'C' condilet, a rigid metal one, with tapered threads ?
since the pot metal ones are so fragile.

 

[hillbilly]

I was standing in line at (s)Lowes the other day. While waiting, I look up and what do I see? A transformer installation using exactly the same parts as Joe's picture.
steve

 

[dcspector]

Yep! I have "Installed" it in the past..........And I "pass" it in the present.:smile:

 

[Rockyd]

Hillbilly,

(s)Lowes is not exactly the shining pillar of electrical knowledge in the industry. I think if you had all the code gurus standing pointing at it, it would be considered a violation. If they were out on a job, they'd do it in a heartbeat, and file it in the"it wasn't pretty, but had no options" closet that like everyone in this industry, has "some junk in the trunk".

I have no problem with it if it is made tight and secure, and has an EGC (wire) sized per 250-122.

Anyone have a NEIS book that covers this?

Is there anyone sitting on a CMP that wants to tackle it?

 

[thinfool]

While Joe is correct about improper use, it is also true that it is a violation to

1. drive more than the posted speed limit
2. be a truant from school
3. cheat on your taxes
4. etc, etc

but all of the above are done everyday. The issue then becomes, not violation, but enforcement.

I will be happy to comply with this issue....immediately after I receive a copy of a compliance agreement about this signed by ALL of the licensed inspectors and contractors in this state. (please don't tell me that the NEC is such a document, tho it should be)*

Until then, money rules, and if my competitor is going to use this method, approved by the AHJ, then I will too.


*"Har, them's the rules Cap'n".
"Well, actually the 'pirates code' is more like 'guidelines'!" (Captain Barbosa, Pirates of the Caribbean)

 

[iwire]

While Joe is correct about improper use,

I disagree, nothing has been presented from the NEC, NEMA or UL that prohibits this practice.


It is simply a practice that Joe does not like.

 

[dcspector]

I disagree, nothing has been presented from the NEC, NEMA or UL that prohibits this practice.


It is simply a practice that Joe does not like.

Thank you Bob.....and we rest.