Chicago - Using LTFC in environmental air space

[Air EE]

I have a project that the engineer is calling for liquid tight flexible conduit to be used to connect fan motors to conduit on the inside of air handling units that supply various areas within a hospital. We are saying that this is a violation of NEC 300.22(b) and City of Chicago code 18-27-351.4.(b).11 that state "Liquidtight flexible metal conduit which has an outer jacket of nonmetallic material shall not be used as a raceway in environmental air handling ducts or spaces (plenums)."

One would thing that, especially in a hospital environment, you would not want to risk the possibility of releasing toxic PVC fumes into patient/OR rooms in the event of a fire.

I realize that the NEC has no bearing in Chicago so I'm trying to get a feel from others that have worked more in Chicago than I have.

 

[LawnGuyLandSparky]

I have a project that the engineer is calling for liquid tight flexible conduit to be used to connect fan motors to conduit on the inside of air handling units that supply various areas within a hospital. We are saying that this is a violation of NEC 300.22(b) and City of Chicago code 18-27-351.4.(b).11 that state "Liquidtight flexible metal conduit which has an outer jacket of nonmetallic material shall not be used as a raceway in environmental air handling ducts or spaces (plenums)."

One would thing that, especially in a hospital environment, you would not want to risk the possibility of releasing toxic PVC fumes into patient/OR rooms in the event of a fire.

I realize that the NEC has no bearing in Chicago so I'm trying to get a feel from others that have worked more in Chicago than I have.

Tell the engineer it's against local code and that non-liquidtight flex is just fine and dandy.

 

[Smart $]

I have a project that the engineer is calling for liquid tight flexible conduit to be used to connect fan motors to conduit on the inside of air handling units that supply various areas within a hospital. We are saying that this is a violation of NEC 300.22(b) and City of Chicago code 18-27-351.4.(b).11 that state "Liquidtight flexible metal conduit which has an outer jacket of nonmetallic material shall not be used as a raceway in environmental air handling ducts or spaces (plenums)."

One would thing that, especially in a hospital environment, you would not want to risk the possibility of releasing toxic PVC fumes into patient/OR rooms in the event of a fire.

I realize that the NEC has no bearing in Chicago so I'm trying to get a feel from others that have worked more in Chicago than I have.

Need elaboration. Not familiar with local code, for one. But as far as NEC, inside an air handling unit is not the same as inside an air handling duct or plenum. Not all sections of air handling units are for handling of environmental air.

 

[Air EE]

This application is definitely within the airstream supplying environmental air. It's located on the downstream side of a plenum type fan. All air flows through this plenum before being delivered into the ducts.

 

[Smart $]

This application is definitely within the airstream supplying environmental air. It's located on the downstream side of a plenum type fan. All air flows through this plenum before being delivered into the ducts.

In that case, it would defintitely be a violation of 300.22(B).

 

[Smart $]

...non-liquidtight flex is just fine and dandy.

...but limited to 4ft max and only if necessary for physical adjustment of equipment (such as to a motor for a belt-driven fan/impeller).

I'm assuming you knew this but just adding it on for those that did not.

 

[Dave58er]

...but limited to 4ft max and only if necessary for physical adjustment of equipment (such as to a motor for a belt-driven fan/impeller).

I'm assuming you knew this but just adding it on for those that did not.

I'll admit I did not know that.

You're speaking of Type FMC right? Could you elaborate on the 4' rule please?
I was not aware of this limitation on length in article 348. Is it a Chicago thing?

The only place I see 4' is 348.30 (A) Exp. #2 (2), but I read that as a requirement for securing not length.

 

[DPW]

Ltfmc

Ltfmc

I have ran into this same situation several times. Whenever the specifying engineer insist on it, all I ask for is to put it in writing that the local AHJ will approve the LTFMC. The odd thing is that NO one has actually been able to provide such documentation.

The question I have is: what does one use flexible metal conduit whenever the application requires a 'washdown' rated plenum or a very high humidity section of the AHU?

 

[Smart $]

i'll admit i did not know that.

you're speaking of type fmc right? Could you elaborate on the 4' rule please?
I was not aware of this limitation on length in article 348. Is it a chicago thing?

The only place i see 4' is 348.30 (a) exp. #2 (2), but i read that as a requirement for securing not length.

Reference NEC 300.22(B).

(B) Ducts or Plenums Used for Environmental Air. Only wiring methods consisting of Type MI cable, Type MC cable employing a smooth or corrugated impervious metal sheath without an overall nonmetallic covering, electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, or rigid metal conduit without an overall nonmetallic covering shall be installed in ducts or plenums specifically fabricated to transport environmental air. Flexible metal conduit shall be permitted, in lengths not to exceed 1.2 m (4 ft), to connect physically adjustable equipment and devices permitted to be in these ducts and plenums. The connectors used with flexible metal conduit shall effectively close any openings in the connection. Equipment and devices shall be permitted within such ducts or plenum chambers only if necessary for their direct action upon, or sensing of, the contained air. Where equipment or devices are installed and illumination is necessary to facilitate maintenance and repair, enclosed gasketed-type luminaires shall be permitted.

 

[Smart $]

...

The question I have is: what does one use [in lieu of?] flexible metal conduit whenever the application requires a 'washdown' rated plenum or a very high humidity section of the AHU?

One of the other approved wirings methods stated 300.22(B)

 

[dejeud]

I have a project that the engineer is calling for liquid tight flexible conduit to be used to connect fan motors to conduit on the inside of air handling units that supply various areas within a hospital. We are saying that this is a violation of NEC 300.22(b) and City of Chicago code 18-27-351.4.(b).11 that state "Liquidtight flexible metal conduit which has an outer jacket of nonmetallic material shall not be used as a raceway in environmental air handling ducts or spaces (plenums)."

One would thing that, especially in a hospital environment, you would not want to risk the possibility of releasing toxic PVC fumes into patient/OR rooms in the event of a fire.

I realize that the NEC has no bearing in Chicago so I'm trying to get a feel from others that have worked more in Chicago than I have.

From what I understand this is the inside of an AHU, so I don't think it qualifies as plenum space. Kinda difficult to see a fire inside a metal enclosure with nothing else but the motor and the belt. I'd be more concerned about belts and the motor producing fumes than 2-3' of LT.
On the other hand I seriously doubt the motor is WP so I'd ask the engineer what would be the purpose of LT feeding a Nema1 motor, and then add that it might violates codes.

 

[Dave58er]

Thanks for the info Smart$.

Guess I could have actually read the section you referenced in post #5. :roll:

 

[esox39]

Chicago Electrical Code 18-27-300.22 Wiring in Ducts, Plenums, and Other Air-Handling Spaces. (b) Ducts or Plenums Used for Environmental Air. (5) Liquidtight flexible metal conduit in lengths not to exceed 4 ft. , to connect physically adjustable equipment and devices permitted to be in these ducts or plenum chambers.

(c) Other Space Used for Environmental Air. (1) Wiring Methods. (e) Liquidtight flexible metal conduit in lengths not to exceed 6 ft., to connect physically adjustable equipment and devices, other than lighting fixtures, permitted to be in these spaces.

I would say according to these codes your install would be code compliant.