• We will be performing upgrades on the forums and server over the weekend. The forums may be unavailable multiple times for up to an hour each. Thank you for your patience and understanding as we work to make the forums even better.

Low Voltage underground in conduit

Status
Not open for further replies.

digisam

Member
We are running camera, intercom, and RS485 communications wire between building in underground conduit. Cable is Plenum rated. Electrician on site said that it had to be rated for damp or wet locations. I didn't think so. Where is it addressed in the NEC code book? We are installing in West Palm Beach, FL. Inspector says what ever the code book calls for and wont give me an answer.
 

bphgravity

Senior Member
Location
Florida
Re: Low Voltage underground in conduit

The code only references cables installed inside the structure or building being served, therefore there is no special requirement for limited energy cables installed outdoors including how they should be listed.
 

digisam

Member
Re: Low Voltage underground in conduit

In the 2005 code book I found a statement under 300.5B that address's underground. This is a change from 2002. Not sure if it applies to low voltage.
 

bphgravity

Senior Member
Location
Florida
Re: Low Voltage underground in conduit

The requirements in Chapter 1-7 do not apply unless they are specifically referenced in Chapter 8.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Re: Low Voltage underground in conduit

While it may not be required by the code, the use of standard cables may cause performance issues. Water increases cross talk and other interference problems. The use of wet location cable helps prevent these problems.
don
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Re: Low Voltage underground in conduit

It's common knowledge that any underground conduit is considered a wet location. No matter how dry you think it is it will only be a matter of time before moisture accumulates. This can be from direct leakage, ingress or from condensation but it WILL happen.

If this were class 1 wiring you would be rquired to use conductors suitable for wet locations. The code does not address this issue for low voltage cables because it won't result in a dangerous condition however you are still going to have operational issues.

Unless you want to deal with them I would suggest that any time you have cables in underground conduit you use cables suitable for wet locations.

-Hal
 
Status
Not open for further replies.
Top