Fiber optic conduit/raceway systems

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h1h2h3

Member
Location
MA
Hi All,

Im a resident electrician for a large building in Boston, MA and recently I received a work order to provide a conduit system for a fiber optic line for one of our tenants. I'm familiar with HDPE Inner tube and the orange Carlton Flex ENT (familiar as in I have seen it before) what I'm not familiar with is the general good practice of such installations. I do know that it is important to keep the bending radious as wide as possible to avoid kinks and strain in and on the cable and that's about it. The run I have to install is fairly complicated because it needs to run up two floors across one and back down two floors. Is it an accepted practice to change over to EMT through floors penetrations and use pull boxes when necessary? Or should I stick with the ENT for the entire installation? Any other pointers you guys have will be greatly appreciated.

Thank You.

P.S.: I am installing only the conduit, not the fiber itself.
 
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GoldDigger

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Location
Placerville, CA, USA
Occupation
Retired PV System Designer
h1h2h3 said:
I do know that it is important to keep the bending radious as wide as possible to avoid kinks and strain in and on the cable and that's about it.
Click to expand...
It is more than just important. Each type of fiber has a manufacturer's spec for minimum bend radius, and you need to meet that absolutely, including at all times while pulling.
If the fiber goes through a tighter bend, it will break on the worst case and leak light energy as it goes around the bend if you go below the minimum.

Since you will not be installing the cable, you really need to find out what kind of cable will be installed and the minimum bend radius the manufacturer requires. Without that you may end up installing pipe that cannot be used without modification.
You may find it hard to get EMT sweeps that satisfy the minimum radius, in which case you would need to custom bend or use flexible conduit and mount it firmly enough that a jam during pulling or someone "tidying up" the run of flex cannot kink it below the minimum radius.

Corning has some general guidelines here.
Note that because of pulling stresses on the fiber, the minimum bend radius during pulling may be greater than the minimum radius once installed.
 
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T

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
h1h2h3 said:
Hi All,

Im a resident electrician for a large building in Boston, MA and recently I received a work order to provide a conduit system for a fiber optic line for one of our tenants. I'm familiar with HDPE Inner tube and the orange Carlton Flex ENT (familiar as in I have seen it before) what I'm not familiar with is the general good practice of such installations. I do know that it is important to keep the bending radious as wide as possible to avoid kinks and strain in and on the cable and that's about it. The run I have to install is fairly complicated because it needs to run up two floors across one and back down two floors. Is it an accepted practice to change over to EMT through floors penetrations and use pull boxes when necessary? Or should I stick with the ENT for the entire installation? Any other pointers you guys have will be greatly appreciated.

Thank You.

P.S.: I am installing only the conduit, not the fiber itself.
Click to expand...
Here is a Mike Holt piece that just ran in the most recent issue of EC&M Magazine that you may like: http://ecmweb.com/code-basics/nec-and-optical-fiber-cable-and-raceway-rules
 
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