wiring methods

Status
Not open for further replies.
H

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
I have specification which I am not able to find code section for in the NEC 2014: low voltage control wiring may be installed without a raceway, in concealed accessible locations, when a UL-listed plenum rated cable is used.

The low voltage wiring above is going to be 24VDC for fire alarm.
 
300.22(C)(1) allows plenum grade wire in a plenum however, are you looking for something more specific for fire alarms?

300.22(C)(1) Wiring Methods. The wiring methods for such other
space shall be limited to totally enclosed, nonventilated, insulated
busway having no provisions for plug-in connections,
Type MI cable without an overall nonmetallic covering, Type
MC cable without an overall nonmetallic covering, Type AC
cable, or other factory-assembled multiconductor control or
power cable that is specifically listed for use within an airhandling
space, or listed prefabricated cable assemblies of metallic
manufactured wiring systems without nonmetallic
sheath
Click to expand...
 
The scenario is inside the building that has fire alaram. The engineer calls for whats stated in poster #1 and says can be concealed in walls.

Sent from my SM-G935U using Tapatalk
 
packersparky said:
I believe that 760.130(B)(2) requires fire alarm cable in a wall to be in a raceway.
Click to expand...

I believe you are misreading the requirement. If a cable comes up through a floor NOT in a cavity, it has to be protected up to 7 feet above the floor. Likewise if the cable penetrates the wall assembly from one side to the other and is exposed on both sides at a height of 7 feet or less. Inside the wall you can go your merry way. Most fire alarm vendors though will tell you to keep FA wire at least 2" away from "high" voltage (>120VAC).

By the way, unless the local code requires or there is a spec mandating it, you can use FPL instead of FPLP. Personally I wouldn't, as the cost difference isn't worth the hassle of re-running the cable if you do accidentally breach a plenum space, or "other environmental air".
 
gadfly56 said:
I believe you are misreading the requirement. If a cable comes up through a floor NOT in a cavity, it has to be protected up to 7 feet above the floor. Likewise if the cable penetrates the wall assembly from one side to the other and is exposed on both sides at a height of 7 feet or less. Inside the wall you can go your merry way. Most fire alarm vendors though will tell you to keep FA wire at least 2" away from "high" voltage (>120VAC).

By the way, unless the local code requires or there is a spec mandating it, you can use FPL instead of FPLP. Personally I wouldn't, as the cost difference isn't worth the hassle of re-running the cable if you do accidentally breach a plenum space, or "other environmental air".
Click to expand...

Everything you said, except I pretty much don't see FPL. FPLR (riser) is the common low end cable and I would use it instead of FPLP anytime when allowed since the cost is about 66% of FPLP. Generally in commercial buildings either you have plenum return spaces for HVAC or you don't. However, if I ran in to a building where the possibility existed, then I would likely do what you recommend.
 
Strathead said:
Everything you said, except I pretty much don't see FPL. FPLR (riser) is the common low end cable and I would use it instead of FPLP anytime when allowed since the cost is about 66% of FPLP. Generally in commercial buildings either you have plenum return spaces for HVAC or you don't. However, if I ran in to a building where the possibility existed, then I would likely do what you recommend.
Click to expand...

True, I don't see a lot of FPL. When I was a wire monkey, the boss used to say, "Wire is cheap, labor is expensive" and we never used anything but FPLP. I kept that in mind when I moved into design and project management. You can go here for a quick comparison on price. You're right there is a significant difference in price; 16-2 unshielded in FPLR is $0.09/ft and FPLP is $0.17/ft in 500 or 1,000 foot spools. But that's only a difference of $80 per 1,000 feet. If you made an "oops" and had to pull back a run of 200' going to 5 or 6 devices and re-install it, how much labor would that burn? Unless you're talking 10,000 feet and up I can't see it is worth the effort to stock two cable types. But to each his own.
 
gadfly56 said:
True, I don't see a lot of FPL. When I was a wire monkey, the boss used to say, "Wire is cheap, labor is expensive" and we never used anything but FPLP. I kept that in mind when I moved into design and project management. You can go here for a quick comparison on price. You're right there is a significant difference in price; 16-2 unshielded in FPLR is $0.09/ft and FPLP is $0.17/ft in 500 or 1,000 foot spools. But that's only a difference of $80 per 1,000 feet. If you made an "oops" and had to pull back a run of 200' going to 5 or 6 devices and re-install it, how much labor would that burn? Unless you're talking 10,000 feet and up I can't see it is worth the effort to stock two cable types. But to each his own.
Click to expand...

I fully get what you are saying and It is all about risk vs. reward. For example, even at over $300 per thousand, I always use Aquaseal cable or single conductors THWN only underground for fire alarm, regardless of the cost. But i would say 80% of the buildings I work in don't have a return air plenum, so I don't see the risk.
 
Strathead said:
I fully get what you are saying and It is all about risk vs. reward. For example, even at over $300 per thousand, I always use Aquaseal cable or single conductors THWN only underground for fire alarm, regardless of the cost. But i would say 80% of the buildings I work in don't have a return air plenum, so I don't see the risk.
Click to expand...

Fair enough.
 
hhsting said:
I have specification which I am not able to find code section for in the NEC 2014: low voltage control wiring may be installed without a raceway, in concealed accessible locations, when a UL-listed plenum rated cable is used.

The low voltage wiring above is going to be 24VDC for fire alarm.
Click to expand...

"Low Voltage" is term we all use, but is not a defined term in the NEC. Fire Alarms are typically power limited. Most low voltage is limited energy, and covered in Art 725. A class 1 remote control circuit is not power limited and uses a chapter 3 wiring method. Class 2 and 3 are power limited and can be run as cables, as there is little danger for fire and shock.
 
tom baker said:
"Low Voltage" is term we all use, but is not a defined term in the NEC. Fire Alarms are typically power limited. Most low voltage is limited energy, and covered in Art 725. A class 1 remote control circuit is not power limited and uses a chapter 3 wiring method. Class 2 and 3 are power limited and can be run as cables, as there is little danger for fire and shock.
Click to expand...

If it's fire alarm at 24 VDC it's almost certainly coming from a Class 2/3 power supply.
 
Status
Not open for further replies.
Top