LV and HV in same conduit
- Thread starter jlmiller
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Re: LV and HV in same conduit
300.3 (C)
(C) Conductors of Different Systems.
(1) 600 Volts, Nominal, or Less. Conductors of circuits rated
600 volts, nominal, or less, ac circuits, and dc circuits shall be
permitted to occupy the same equipment wiring enclosure,
cable, or raceway. All conductors shall have an insulation rating
equal to at least the maximum circuit voltage applied to
any conductor within the enclosure, cable, or raceway.
Check the insulation rating on the cat 5.
Btw, even if legal.. would likey cause interference in the comm wires.
300.3 (C)
(C) Conductors of Different Systems.
(1) 600 Volts, Nominal, or Less. Conductors of circuits rated
600 volts, nominal, or less, ac circuits, and dc circuits shall be
permitted to occupy the same equipment wiring enclosure,
cable, or raceway. All conductors shall have an insulation rating
equal to at least the maximum circuit voltage applied to
any conductor within the enclosure, cable, or raceway.
Check the insulation rating on the cat 5.
Btw, even if legal.. would likey cause interference in the comm wires.
Re: LV and HV in same conduit
jb, I wish it were that simple, and if it is maybe someone here will teach me, but, i'm afraid you also must bring 725.25 and 725.55 into consideration. To be honest, I've struggle with Class I,II , II for years and still; don't think I have as full understanding.
jb, I wish it were that simple, and if it is maybe someone here will teach me, but, i'm afraid you also must bring 725.25 and 725.55 into consideration. To be honest, I've struggle with Class I,II , II for years and still; don't think I have as full understanding.
pierre
Senior Member
- Location
- Westchester County, New York
Re: LV and HV in same conduit
The NEC does not really consider what some of us call low voltage. What we need to concentrate on is whether it is Line voltage, Class 1, Class 2, Class 3. Also Fire Alarm and Communication wiring.
So we need to reference 725.55, 760.55, 800.133, 820.133 and 830.133
300.3(C) is for system voltage considerations such as 208v/480v/600v in the same raceway.
The NEC does not really consider what some of us call low voltage. What we need to concentrate on is whether it is Line voltage, Class 1, Class 2, Class 3. Also Fire Alarm and Communication wiring.
So we need to reference 725.55, 760.55, 800.133, 820.133 and 830.133
300.3(C) is for system voltage considerations such as 208v/480v/600v in the same raceway.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: LV and HV in same conduit
JBWhite:
You missed part of 300.3(C)(1), the FPN.
Read the FPN and its code section. Its a violation to install a Class 2 or 3 limited energy circuit with power, lighting and branch circuits.
The most important code rule in the NEC is 90.3
Its assumed you understand that 90.3 states a rule in chapter 5-7 can modify a rule in chapters 1-4.
And Pierre, thanks for your note.
What is high voltage to an alarm installer is low voltage to a utility lineman.
"Low voltage" can be dangerous if it exceeds the limits of a Class 2 or 3 circuit. Think of a low voltage car battery and how easily it can start a fire.
JBWhite:
You missed part of 300.3(C)(1), the FPN.
Read the FPN and its code section. Its a violation to install a Class 2 or 3 limited energy circuit with power, lighting and branch circuits.
The most important code rule in the NEC is 90.3
Its assumed you understand that 90.3 states a rule in chapter 5-7 can modify a rule in chapters 1-4.
And Pierre, thanks for your note.
What is high voltage to an alarm installer is low voltage to a utility lineman.
"Low voltage" can be dangerous if it exceeds the limits of a Class 2 or 3 circuit. Think of a low voltage car battery and how easily it can start a fire.
Re: LV and HV in same conduit
Clarification on my question: (I don't know what is right or wrong, thus my question)
We are monitoring a tower light strobe system. The monitor is mounted adjacent to the strobe controller; What I have seen is that there is one piece of conduit between the strobe controller and the monitor. (the monitor is a box with a modem/phone or wireless, or vsat to know the status of the tower lights per FAA requirement) Inside this one conduit is 3 runs of #12 thhn to tap off the 120vac feeding the strobe in order to power the monitor. Also inside this conduit are smaller conductors (cat 5, alarm wire, etc..using around 22-28awg) the pick up the form c relay contacts inside the strobe. (normally open or normally closed) The monitor puts out 5vdc on its input points and uses this 5vdc to determine the state of system based on the programming logic (again normally open or normally closed). The wire is NOT being used for any communications protocol (ethernet, async, telco, etc). This wire is only being used to pick up a NO or NC state of the tower lights.
Given: I am a nerd, but as a master electrician I have yet to understand if this is ok or not.
Thanks all,
Jimmy
Clarification on my question: (I don't know what is right or wrong, thus my question)
We are monitoring a tower light strobe system. The monitor is mounted adjacent to the strobe controller; What I have seen is that there is one piece of conduit between the strobe controller and the monitor. (the monitor is a box with a modem/phone or wireless, or vsat to know the status of the tower lights per FAA requirement) Inside this one conduit is 3 runs of #12 thhn to tap off the 120vac feeding the strobe in order to power the monitor. Also inside this conduit are smaller conductors (cat 5, alarm wire, etc..using around 22-28awg) the pick up the form c relay contacts inside the strobe. (normally open or normally closed) The monitor puts out 5vdc on its input points and uses this 5vdc to determine the state of system based on the programming logic (again normally open or normally closed). The wire is NOT being used for any communications protocol (ethernet, async, telco, etc). This wire is only being used to pick up a NO or NC state of the tower lights.
Given: I am a nerd, but as a master electrician I have yet to understand if this is ok or not.
Thanks all,
Jimmy
Re: LV and HV in same conduit
Such cable is available, but not all that common.
Solutions that I would recommend:
1. add a conduit for lv conductors only or
2. run lv conductors without conduit or
3. obtain conductors for lv use with the correct insulation.
If the lv conductors are in the same conduit with the 120v conductors, they MUST have 120v insulation. 120v insulation does not exist. Standard power wiring has 600 volt insulation. So the monitoring/alarm wiring must also have 600v insulation.
Such cable is available, but not all that common.
Solutions that I would recommend:
1. add a conduit for lv conductors only or
2. run lv conductors without conduit or
3. obtain conductors for lv use with the correct insulation.
pierre
Senior Member
- Location
- Westchester County, New York
Re: LV and HV in same conduit
Tom, you are welcome!!!
"If the lv conductors are in the same conduit with the 120v conductors, they MUST have 120v insulation. 120v insulation does not exist. Standard power wiring has 600 volt insulation. So the monitoring/alarm wiring must also have 600v insulation."
This is not necessarily so, it depends on the power source for the 5vdc. My guess is the power is such, that the conductors off of the load side of the source will be required to be separated from the line voltage conductors. There seems to be [a confusion with 300.3(C)] thought process that line voltage and control wiring can be in the same conduit. This is most likely not true.
Take a look at the 5vdc power source to see how it is classified.
Tom, you are welcome!!!
"If the lv conductors are in the same conduit with the 120v conductors, they MUST have 120v insulation. 120v insulation does not exist. Standard power wiring has 600 volt insulation. So the monitoring/alarm wiring must also have 600v insulation."
This is not necessarily so, it depends on the power source for the 5vdc. My guess is the power is such, that the conductors off of the load side of the source will be required to be separated from the line voltage conductors. There seems to be [a confusion with 300.3(C)] thought process that line voltage and control wiring can be in the same conduit. This is most likely not true.
Take a look at the 5vdc power source to see how it is classified.
- Location
- Illinois
- Occupation
- retired electrician
Re: LV and HV in same conduit
thinfool,
Don
thinfool,
I'm sorry, but that is not completely correct. As Pierre pointed out in his post there are Chapter 7 or 8 rules that must be complied with.
Don
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: LV and HV in same conduit
JLMiller:
A Class 1 non-power limited system (in Art 725)is a a chapter 3 wiring method and can be in the same raceway as power lighting and branch circuits. The class 1 non power limited system is commonly used for motor control circuits, The difference is that it does not require de-rating for fill if the circuit ampacity is 10% or less of the conductor ampacity.
A simple way to make this system NEC compliant and safe is to make your 5v system a Class 1 remote control and monitoring system.
JLMiller:
A Class 1 non-power limited system (in Art 725)is a a chapter 3 wiring method and can be in the same raceway as power lighting and branch circuits. The class 1 non power limited system is commonly used for motor control circuits, The difference is that it does not require de-rating for fill if the circuit ampacity is 10% or less of the conductor ampacity.
A simple way to make this system NEC compliant and safe is to make your 5v system a Class 1 remote control and monitoring system.
Re: LV and HV in same conduit
I think I see your point and it is correct. My only issue was that insulation values must be the same for all conductors within a given conduit, for the highest voltage present within that conduit. I didn't have in mind what the use of the lv wires was.
The OP's description of the installation indicates to me that there could well be problems with the lv information if it is not corrected. (induced hum, transients, etc)
Pierre,
I think I see your point and it is correct. My only issue was that insulation values must be the same for all conductors within a given conduit, for the highest voltage present within that conduit. I didn't have in mind what the use of the lv wires was.
The OP's description of the installation indicates to me that there could well be problems with the lv information if it is not corrected. (induced hum, transients, etc)
pierre
Senior Member
- Location
- Westchester County, New York
Re: LV and HV in same conduit
Thinfool
Try to remember that 300.3(C) may have nothing to do with this installation.
Try to remember that Chapter 5, 6 & 7 may modify Chapters 1-4. Which most likely is what will be happening in this installation.
Thinfool
Try to remember that 300.3(C) may have nothing to do with this installation.
Try to remember that Chapter 5, 6 & 7 may modify Chapters 1-4. Which most likely is what will be happening in this installation.
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