LT Flex on machine wiring.....

What general code restrictions are there about running LT flex when wiring machine components. This is an OEM built custom machine. Which technically isn't covered by NEC anyway. But I would like to know what restrictions are related to using LT flex for machine control wiring.

Anyone ?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
What general code restrictions are there about running LT flex when wiring machine components. This is an OEM built custom machine. Which technically isn't covered by NEC anyway. But I would like to know what restrictions are related to using LT flex for machine control wiring.

Anyone ?
what is LT Flex?

in general you are correct that the NEC does not cover wiring internal to machines. I am not sure there is any mandatory standard that does cover it.
 

augie47

Moderator
Staff member
Location
Tennessee
From an inspectors standpoint, in my area, with the wording of 90.7, if the assembled piece of equipment bears a NRTL listing, there would be no problem with LT sealtite.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
From an inspectors standpoint, in my area, with the wording of 90.7, if the assembled piece of equipment bears a NRTL listing, there would be no problem with LT sealtite.
just how would you go about dealing with a machine that did not have an NRTL listing? Especially since virtually no custom machines come with such a listing. just what standard could you inspect them to?
 
Last edited by a moderator:

kwired

Electron manager
Location
NE Nebraska
What would be wrong with wiring an entire facility with LT flex? Unless there is specific application where it is prohibited, it is just a raceway wiring method just like EMT, RMC, IMC, RNMC. It may have a little different securing and support requirements than some of those mentioned, and likely cost more to run than some of those mentioned but otherwise is a raceway for general use, and has specific uses that some raceways may not have like the "liquid tight" application part of it.
 

augie47

Moderator
Staff member
Location
Tennessee
just how would you go about dealing with a machine that did not have an NRTL listing? Especially since virtually no custom machines come with such a listing. just what standard could you inspect them to?
In our State, any exception to the NRTL requirement must be provided by the State Fire Marshal's Office where a determination is made as to what inspections will suffice.
 
Sorry for the delay,

Yes Liquid Tight flex such as anaconda flex. I heard a remark from a guy today that flex could not be run over 4 foot according to code. I have never seen such a description myself.

And from what I have learned over the years being that we build an engineered product we are not covered by any code. Of course if we want to be UL or similar we would need to meet those independent requirements. But as a machine manufacturer we are basically limited to civil liability and legal liabilities if someone were hurt on our machine.

With all that said, The NEC code comes into play when the customer puts the machine into his factory. The connections from the machines main breaker to his supply circuits etc then are governed by NEC code.

As for machine tool wiring and controls engineering I have a lot of latitude in my design and building of the machines..
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I don't get the pleasure. It is inspected by a group folks a lot higher up the food chain.
From what I have seen accepted, I often think it has no relation to any Code.:D
nfpa79 is probably what they would use. it makes a lot of sense for machine wiring.

it allows for things like the extensive use of cord that would be suspect in a NEC install.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
What general code restrictions are there about running LT flex when wiring machine components. This is an OEM built custom machine. Which technically isn't covered by NEC anyway. But I would like to know what restrictions are related to using LT flex for machine control wiring.

Anyone ?
Listed or non-listed liquid tight flexible conduit? For NEC applications you can only use the listed type. Machine manufacturers often use the non-listed type.
 

kwired

Electron manager
Location
NE Nebraska
I heard a remark from a guy today that flex could not be run over 4 foot according to code. I have never seen such a description myself.
No such limitation. There are limitations on length when using a metal flex as an equipment grounding conductor, but if there is an equipment grounding conductor pulled within the raceway then this is not a limitation. That limitation BTW is 6 feet and not 4 feet.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Listed or non-listed liquid tight flexible conduit? For NEC applications you can only use the listed type. Machine manufacturers often use the non-listed type.
no reason not to if you are not subject to NEC requirements.

to be honest, I figured once the rule in the code was changed to require this kind of thing be listed that the manufacturers would stop making the unlisted version.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
No such limitation. There are limitations on length when using a metal flex as an equipment grounding conductor, but if there is an equipment grounding conductor pulled within the raceway then this is not a limitation. That limitation BTW is 6 feet and not 4 feet.
I seem to recall it has to be secured every 4 feet. maybe that is what the guy was thinking about.

I am not a huge fan of the stuff. If I want something liquid tight and flexible it will be the all plastic version if I have my druthers.
 

kwired

Electron manager
Location
NE Nebraska
no reason not to if you are not subject to NEC requirements.

to be honest, I figured once the rule in the code was changed to require this kind of thing be listed that the manufacturers would stop making the unlisted version.

Manufacturers make a lot of non listed things, as long as there is a demand for them. It is codes that end up making the demand in certain areas go down.

You may see more of these non listed items by equipment manufacturers, or by POCO's with some of their equipment, but go to a supply house that sells to these people and you will find those same items available to you also, but you may have a harder time using them if everything you do is inspected.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Manufacturers make a lot of non listed things, as long as there is a demand for them. It is codes that end up making the demand in certain areas go down.

You may see more of these non listed items by equipment manufacturers, or by POCO's with some of their equipment, but go to a supply house that sells to these people and you will find those same items available to you also, but you may have a harder time using them if everything you do is inspected.
The rule to use listed LFMC was put into the code in 1996. Most of the supply houses around here will give you the cheaper non-listed product, unless you specifically request the listed product.
 

kwired

Electron manager
Location
NE Nebraska
The rule to use listed LFMC was put into the code in 1996. Most of the supply houses around here will give you the cheaper non-listed product, unless you specifically request the listed product.
Apparently there is significant amount of the non listed stuff still being purchased or they wouldn't waste the space to stock it.

That means it is either going to places where it doesn't need listing, or doesn't get inspections for whatever reason, or inspectors are not rejecting it.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Apparently there is significant amount of the non listed stuff still being purchased or they wouldn't waste the space to stock it.

That means it is either going to places where it doesn't need listing, or doesn't get inspections for whatever reason, or inspectors are not rejecting it.
It is a bit cheaper and many inspectors don't check to see if you are using the listed product.
I asked a manufacturer's rep why they still made the non-listed product, and his answer was that it is not a violation to make and sell the product...just a violation to install it.
 
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