I'm new to this low-voltage stuff. I've been asked to look over some HVAC wiring being done by a contractor for my employer. One of the first things I noticed is they have the conduit filled to at least 80% fill. I brought this up to the guy (master electrician) installing the wiring. His response was that the conduit fill rules only apply to current carrying conductors. I told him I was not aware of any such rule and have not been able to find an exemption for him to fill these pipes to the max. Am I right? Or is there a rule I am missing? What say you oh wise ones?
Coduit fill for low voltage cables
- Thread starter DLTravis
- Start date
- Status
KentAT
Senior Member
- Location
- Northeastern PA
Just how low of voltage is HVAC wiring? I don't know much about it. I always thought it was aroung 24 or 12 VAC or VDC. Just a thought, but wouldn't it still be considered as current-carrying??
On another note, communications wiring such as CATV does have an exception from conduit fill requirements in a raceway. See 820.110.
Not in the 2005 code, but the 2008 code adds the same exemption from conduit fill requirements for low-power network-powered broadband communications cables. See 830.110
On another note, communications wiring such as CATV does have an exception from conduit fill requirements in a raceway. See 820.110.
Not in the 2005 code, but the 2008 code adds the same exemption from conduit fill requirements for low-power network-powered broadband communications cables. See 830.110
DUCKMAN said:
This is what the inspector and I agreed on! The wording in 300.17 could be better IMO to direct you to fill tables or give %'s of max fill. The contractor read 300.17 as meaning as long as he doesn't damage the wires and heating is not an issue he could fill them as much as he wanted. After calling the inspector it looks like this will be getting changed.
BTW Class II power limited 24 VDC control wiring.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
DLTravis said:
I say this is a physical impossibilty. That would be the equivelant of (32) 12AWG conducators in a 3/4 raceway.
ryan_618 said:
Sorry this took so long to respond to but I wanted to be accurate so I made my way down took some measurements and counted some conductors for my inspector friend.
Approx. dia. of conductors (averaged) is .1875" and there are 16 of them. By my math that is 83% full. My measurements favored the small side so actual fill is probably more like 85%.
I want to give the latest in this. The local inspector decided to side with the contractor on this one. The contractor convinced the inspector his class 2 wiring is exempt from 300.17 because there is no heating effect. I wrote this letter to the head inspector but have not gotten a reply yet:
_________________________________________________________________
I recently had a discussion with one of the cities inspectors ("Bob"). I explained to Mike that we are experiencing some problems with our low voltage contractors overfilling conduit (with class 2 wiring) on systems associated with air handling equipment. Bob was not the inspector for this particular area so I was referred to Joe. To make a long story fairly short it was determined that class 2 wiring is exempt from the conduit fill guidelines set forth by NFPA-70 (NEC). It was my understanding that this was discussed among the group of inspectors and possibly yourself.
I would like a chance to plea my case with you and hope you will reconsider your ruling on this matter. I know the code is not intended to make my life easy, this is not my concern. As you know article 90 states ?This code contains provisions that are considered necessary for safety?. It is my understanding that the overfilling of conduits containing class 2 wiring is not viewed as an ?unsafe? practice. If this is accurate I would hope to change your opinion on this topic.
I?m not sure if article 725.11 fits in this case or not. However, I do know some of the wiring associated with air handling equipment is intended for reducing fire and life hazards and beyond that preventing building damage. To name a few there are systems which will shut down air handlers in case of fires to prevent fire from spreading, systems to turn on stairwell pressurization fans to keep smoke out of stairwells, and there are systems intended to prevent heating/cooling coils from rupturing and spilling their contents. Any damage done to wires during installation could prevent these systems from working as designed.
Article 725.3 states ?Circuits and equipment shall comply with the articles or sections listed in 725.3 (A) through 725.3 (G). Only those sections of Article 300 referenced in this article shall apply to Class 1, Class 2, and Class 3 circuits.?
725.3 (A) reads ?Number and Size of Conductors in Raceway. Section 300.17.?
If you then read 300.17 you will see where it says ??not be more than will permit dissipation of the heat and ready installation or withdrawal of the conductors without damage to the conductors or to their insulation.?
The conduit which started this whole mess is 81% full (a generously small measurement)! I am pretty sure we would agree this type of fill is likely to damage something during the installation and if not then most likely the first time something needs to be changed. I think where we may disagree is on whether or not this prevents a life safety issue. I hope you will consider what I have written here and discuss it with others. In my opinion it is not only poor practice is also dangerous.
Thank you for your time,
*me*
_________________________________________________________________
The reason I post this is I would like to know what others think about this topic. Let's hear it.
_________________________________________________________________
I recently had a discussion with one of the cities inspectors ("Bob"). I explained to Mike that we are experiencing some problems with our low voltage contractors overfilling conduit (with class 2 wiring) on systems associated with air handling equipment. Bob was not the inspector for this particular area so I was referred to Joe. To make a long story fairly short it was determined that class 2 wiring is exempt from the conduit fill guidelines set forth by NFPA-70 (NEC). It was my understanding that this was discussed among the group of inspectors and possibly yourself.
I would like a chance to plea my case with you and hope you will reconsider your ruling on this matter. I know the code is not intended to make my life easy, this is not my concern. As you know article 90 states ?This code contains provisions that are considered necessary for safety?. It is my understanding that the overfilling of conduits containing class 2 wiring is not viewed as an ?unsafe? practice. If this is accurate I would hope to change your opinion on this topic.
I?m not sure if article 725.11 fits in this case or not. However, I do know some of the wiring associated with air handling equipment is intended for reducing fire and life hazards and beyond that preventing building damage. To name a few there are systems which will shut down air handlers in case of fires to prevent fire from spreading, systems to turn on stairwell pressurization fans to keep smoke out of stairwells, and there are systems intended to prevent heating/cooling coils from rupturing and spilling their contents. Any damage done to wires during installation could prevent these systems from working as designed.
Article 725.3 states ?Circuits and equipment shall comply with the articles or sections listed in 725.3 (A) through 725.3 (G). Only those sections of Article 300 referenced in this article shall apply to Class 1, Class 2, and Class 3 circuits.?
725.3 (A) reads ?Number and Size of Conductors in Raceway. Section 300.17.?
If you then read 300.17 you will see where it says ??not be more than will permit dissipation of the heat and ready installation or withdrawal of the conductors without damage to the conductors or to their insulation.?
The conduit which started this whole mess is 81% full (a generously small measurement)! I am pretty sure we would agree this type of fill is likely to damage something during the installation and if not then most likely the first time something needs to be changed. I think where we may disagree is on whether or not this prevents a life safety issue. I hope you will consider what I have written here and discuss it with others. In my opinion it is not only poor practice is also dangerous.
Thank you for your time,
*me*
_________________________________________________________________
The reason I post this is I would like to know what others think about this topic. Let's hear it.
JohnJ0906
Senior Member
- Location
- Baltimore, MD
DLTravis - is the 81% fill an estimation, or a calculation using Tables 4 and 5 from chapter 9, NEC?
- Location
- Illinois
- Occupation
- retired electrician
I see nothing in Article 725 that says the raceway xxx.22 sections do not apply. 725.3 says that only the listed sections of Article 300 apply. 90.3 says that the rules in the Chapter 3 Articles apply to the Chapter 7 Articles unless the Chapter 7 Article says otherwise.
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