Expansion Fitting

[Mike01]

I was on site recently and at a building expansion joint the contractor installed a piece of what looked to be LFMC across the expansion joint in a bank of large conduit runs. I have never come across this before, is this typically a method used instead of expansion deflection fittings? I will try to get a picture the next time I am on site.

 

[kwired]

I was on site recently and at a building expansion joint the contractor installed a piece of what looked to be LFMC across the expansion joint in a bank of large conduit runs. I have never come across this before, is this typically a method used instead of expansion deflection fittings? I will try to get a picture the next time I am on site.

I can not say if it is typical, but sure seems like it would be effective.

 

[Smart $]

Also can't say whether typical or not. I've only seen it once.

Assuming the main conduits are metallic and larger than 1-1/4", I believe it is a code violation if there aren't any bonding jumpers across the LFMC joints.

 

[masterinbama]

Do this all the time. We also bond any conduits installed this way on both ends.

 

[Ponchik]

I believe it is a code violation if there aren't any bonding jumpers across the LFMC joints.

Assuming there isn't an EGC installed already. Correct?

 

[kaichosan]

Yes ... bonded flex at expansion should be long enough to accommodate the expansion movement.

Although, an expansion fittting could be quicker to install.

 

[plumb bob]

Do this all the time. We also bond any conduits installed this way on both ends.

I have to be honest, I have never been on a job where this situation came up. Maybe because I've never worked in an area with any siesmic activity. Do you take any precautions when pulling wire in a run like this? Or just pull it like a normal pipe run, and don't worry about the flex section? Just curious. :?

 

[Smart $]

Assuming there isn't an EGC installed already. Correct?

Not compliant IMO even if a wire-type EGC is installed... but it's not specifically spelled out in the Code.

Its about continuity of raceway and its ability to carry fault current. If you look at 250.118, LFMC is permitted as an EGC for sizes 3/8" to 1/2" up to 20A circuits, 3/4" to 1-1/4" for circuits up to 60A. Larger sizes cannot serve as an EGC. If those sizes cannot serve as an EGC, then logical deduction says they cannot serve to bond sections of metallic conduit.

 

[kwired]

I don't believe you need to bond across right at the flexible conduit location, you just need to ensure that each raceway is bonded to the EGC, which should happen anyway if you have pulled an EGC through the raceway, because it will need to bond to the enclosure where the raceway terminates or maybe to a bonding bushing if the enclosure is non metallic. There is no requirement to bond the raceway at each end that I am aware of, just needs bonding to EGC anyplace in the run.

 

[Smart $]

I don't believe you need to bond across right at the flexible conduit location, you just need to ensure that each raceway is bonded to the EGC, which should happen anyway if you have pulled an EGC through the raceway, because it will need to bond to the enclosure where the raceway terminates or maybe to a bonding bushing if the enclosure is non metallic. There is no requirement to bond the raceway at each end that I am aware of, just needs bonding to EGC anyplace in the run.

I disagree. If what you say is true, why is it required to install a bonding jumper around an actual expansion fitting?

 

[kwired]

I disagree. If what you say is true, why is it required to install a bonding jumper around an actual expansion fitting?

From 250.96(A): "shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them".

If there are no loose fitting joints of any kind why would you need to bond to more than one point to comply with this?

250.98 does mention loosely fitting joints such as expansion fittings, but an equipment grounding conductor installed within the raceway containing the expansion fitting also is a bonding jumper between the two sections if it is bonded to an enclosure on each side and those enclosures are electrically continuous with the raceway (like they are supposed to be anyway)?

IMO if the raceway is the EGC then you would need an external bonding jumper across the expansion fitting, if there is an EGC pulled through the raceway, then you do not necessarily need an additional bonding jumper unless there is no continuity for some reason to each section of the raceway, and that reason would be very rare I would think.

 

[Smart $]

From 250.96(A): "shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them".

If there are no loose fitting joints of any kind why would you need to bond to more than one point to comply with this?

250.98 does mention loosely fitting joints such as expansion fittings, but an equipment grounding conductor installed within the raceway containing the expansion fitting also is a bonding jumper between the two sections if it is bonded to an enclosure on each side and those enclosures are electrically continuous with the raceway (like they are supposed to be anyway)?

IMO if the raceway is the EGC then you would need an external bonding jumper across the expansion fitting, if there is an EGC pulled through the raceway, then you do not necessarily need an additional bonding jumper unless there is no continuity for some reason to each section of the raceway, and that reason would be very rare I would think.

All noteworthy, but you left out a pertinent part of 250.96(A)...

250.96 Bonding Other Enclosures.
(A) General. Metal raceways, cable trays, cable armor,
cable sheath, enclosures, frames, fittings, and other metal
non?current-carrying parts that are to serve as equipment
grounding conductors, with or without the use of supplementary
equipment grounding conductors, shall be bonded
where necessary to ensure electrical continuity and the capacity
to conduct safely any fault current likely to be imposed
on them.

 

[kwired]

All noteworthy, but you left out a pertinent part of 250.96(A)...

What did I leave out? If it is bonded (at any point), and all connections are tight (like they are required to be by other sections of code), if it becomes energized it will have a low impedance path back to the source for clearing ground faults.

How many times have you run PVC conduit underground, but change to RMC or IMC when emerging from the ground? I have done this many times. Do I need a bonding jumper to connect to the buried end of the metal raceway? No, it is bonded at the above ground enclosure it connects to either by locknuts securing it to the enclosure or possibly a bonding bushing if it was deemed necessary, but it is only bonded at one point. Go to other end of the run and we have the same thing. The pulled EGC through the raceway is the bonding jumper that connects the two.

It is the same thing, except the non conductive portion is longer than an short piece of flex in the middle of a run generally would be in a situation like the OP has.

 

[don_resqcapt19]

I disagree. If what you say is true, why is it required to install a bonding jumper around an actual expansion fitting?

There are expansion fittings that do not require a bonding jumper.

 

[Cow]

Smart, how is this any different than using rigid stubups with pvc connecting them underground? You don't run a bonding jumper on the outside of the pvc do you? So why would you need to bond across an expansion fitting if both ends are already connected to an EGC?

 

[Smart $]

There are expansion fittings that do not require a bonding jumper.

I was aware of those. I like how they have optional bonding jumpers for redundancy, and more important to this discussion, visual indication. I suppose I could have stated otherwise, but wouldn't have changed the concept of discussion ? grounding continuity through the expansion joint is required.

 

[Smart $]

What did I leave out? If it is bonded (at any point), and all connections are tight (like they are required to be by other sections of code), if it becomes energized it will have a low impedance path back to the source for clearing ground faults.

It says with or without supplementary EGC. Grounding continuity of the raceway is required regardless of any wire EGC in the conduit run.

How many times have you run PVC conduit underground, but change to RMC or IMC when emerging from the ground? I have done this many times. Do I need a bonding jumper to connect to the buried end of the metal raceway? No, it is bonded at the above ground enclosure it connects to either by locknuts securing it to the enclosure or possibly a bonding bushing if it was deemed necessary, but it is only bonded at one point. Go to other end of the run and we have the same thing. The pulled EGC through the raceway is the bonding jumper that connects the two.

It is the same thing, except the non conductive portion is longer than an short piece of flex in the middle of a run generally would be in a situation like the OP has.

Smart, how is this any different than using rigid stubups with pvc connecting them underground? You don't run a bonding jumper on the outside of the pvc do you? So why would you need to bond across an expansion fitting if both ends are already connected to an EGC?

A run of PVC conduit is not "expected" to serve as an EGC. We even have requirements addressing the bonding of metal sections installed in PVC runs. We are discussing grounding continuity of metal raceway.

 

[Ponchik]

250.96 Bonding Other Enclosures.
(A) General. Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non?current-carrying parts that are to serve as grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them. Any nonconductive paint, enamel, or similar coating shall be removed at threads, contact points, and contact surfaces or be connected by means of fittings designed so as to make such removal unnecessary.

FWIW,
that are to serve as grounding conductors, the non metallic expansion fitting is installed then it can not serve as an EGC, hence, we install the EGC (conductor type). Now, as far as "be bonded where necessary to ensure electrical continuity" the metallic conduits are bonded at both ends.

 

[kwired]

250.96 Bonding Other Enclosures.
(A) General. Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non?current-carrying parts that are to serve as grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them. Any nonconductive paint, enamel, or similar coating shall be removed at threads, contact points, and contact surfaces or be connected by means of fittings designed so as to make such removal unnecessary.

FWIW,
that are to serve as grounding conductors, the non metallic expansion fitting is installed then it can not serve as an EGC, hence, we install the EGC (conductor type). Now, as far as "be bonded where necessary to ensure electrical continuity" the metallic conduits are bonded at both ends.

Kind of my thoughts too.

Another example I often see is metal raceway and a transition to flexible conduit with either non metallic flex or conditions where metallic flex is not permitted to serve as an EGC. The metal raceway is bonded at the start of the run by the locknut or hub at the start of the run and an EGC is pulled through to bond to anything beyond the flex that needs connected to EGC.

 

[Smart $]

250.96 Bonding Other Enclosures.
(A) General. Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non?current-carrying parts that are to serve as grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them. Any nonconductive paint, enamel, or similar coating shall be removed at threads, contact points, and contact surfaces or be connected by means of fittings designed so as to make such removal unnecessary.

FWIW,
that are to serve as grounding conductors, the non metallic expansion fitting is installed then it can not serve as an EGC, hence, we install the EGC (conductor type). Now, as far as "be bonded where necessary to ensure electrical continuity" the metallic conduits are bonded at both ends.

Kind of my thoughts too.

You two keep resorting to the bonding being established through the wire EGC. 250.96(A) CLEARLY says with or without supplementary EGC, which includes the wire EGC. Without the wire EGC, the metal conduit run would serve as the EGC. That's what it means. You must install a run of metal conduit as if it is the only EGC.

Another example I often see is metal raceway and a transition to flexible conduit with either non metallic flex or conditions where metallic flex is not permitted to serve as an EGC. The metal raceway is bonded at the start of the run by the locknut or hub at the start of the run and an EGC is pulled through to bond to anything beyond the flex that needs connected to EGC.

And where flexible conduits are not permitted to serve as an EGC, you have the same condition.