If you have a multi conductor cable with 8 conductors, 14ga, THHN,600v, Direct Burial cable. Can you put 480vac on 4 wires, 2 wires with 24vdc for inhibit circuit on a drive and 2 wires with no voltage for a NO set of dry contacts for a stop circuit. Is this code to put different voltages of wire in this type of cord? It is color coded.
Multi Conductor Cable
- Thread starter robr
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Ed MacLaren
Senior Member
Re: Multi Conductor Cable
Most codes permit what you described, providing the conductors are for power and control for the same apparatus, and all of the conductors are insulated for the highest of the voltages.
I am not sure about the NEC.
Ed
Most codes permit what you described, providing the conductors are for power and control for the same apparatus, and all of the conductors are insulated for the highest of the voltages.
I am not sure about the NEC.
Ed
- Location
- Illinois
- Occupation
- retired electrician
Re: Multi Conductor Cable
We need to know about the classification of the low voltage control circuit. If this is an Article 725 Class 2 circuit, you cannot do it that way. If the control circuit is not a Class 2 circuit, it would be permitted by the NEC.
Don
We need to know about the classification of the low voltage control circuit. If this is an Article 725 Class 2 circuit, you cannot do it that way. If the control circuit is not a Class 2 circuit, it would be permitted by the NEC.
Don
Re: Multi Conductor Cable
Look at the 24 volt transformer. It will probably say "listed Class 2 or 3 transformer". If so, you have a Class 2 or 3 circuit. (typically on doorbells and t-stats for furnaces and boilers in residential). 725.41(A).
Cables with Class 2 or 3 conductors cannot also contain conductors of electric light, power, Class 1, etc. 725.55(A).
Article 780.6 does allow Hybrid Cables to contain power and signaling conductor under a common jacket for Closed-Loop and Programmed Power Distribution systems.
Look at the 24 volt transformer. It will probably say "listed Class 2 or 3 transformer". If so, you have a Class 2 or 3 circuit. (typically on doorbells and t-stats for furnaces and boilers in residential). 725.41(A).
Cables with Class 2 or 3 conductors cannot also contain conductors of electric light, power, Class 1, etc. 725.55(A).
Article 780.6 does allow Hybrid Cables to contain power and signaling conductor under a common jacket for Closed-Loop and Programmed Power Distribution systems.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Multi Conductor Cable
"Article 780.6 does allow Hybrid Cables to contain power and signaling conductor under a common jacket for Closed-Loop and Programmed Power Distribution systems" this is a special cable made by a company who bankrupt a number of years ago. the article is being kept in the code for those systems that are still being used. I don't know if the cable is still manufactured or not.
[ September 17, 2003, 09:45 AM: Message edited by: tom baker ]
"Article 780.6 does allow Hybrid Cables to contain power and signaling conductor under a common jacket for Closed-Loop and Programmed Power Distribution systems" this is a special cable made by a company who bankrupt a number of years ago. the article is being kept in the code for those systems that are still being used. I don't know if the cable is still manufactured or not.
[ September 17, 2003, 09:45 AM: Message edited by: tom baker ]
- Location
- Wisconsin
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- PE (Retired) - Power Systems
Re: Multi Conductor Cable
Power Limited Class 2 rated equipment may be installed using Class 2 or Class 1 methods. Remote control and signalling circuits may be installed using Class 1 methods. (Class 3 rated equipment must be installed using Class 3 methods.)
So, I feel the installation can be installed as a Power Limited Class 1 circuit, if all conductors are insulated for the highest applied voltage.
Power Limited Class 2 rated equipment may be installed using Class 2 or Class 1 methods. Remote control and signalling circuits may be installed using Class 1 methods. (Class 3 rated equipment must be installed using Class 3 methods.)
So, I feel the installation can be installed as a Power Limited Class 1 circuit, if all conductors are insulated for the highest applied voltage.
Re: Multi Conductor Cable
Even if it is allowed by the code, many industrial electricians and engineers make it a point to keep the 24 volt circuits separate from 120V to prevent problems with noise.
Imagine the capacitive and inductive coupling between the wires since they are bundled together so close. Its even worse if they run a long distance, worse for 480V than 120V, worse if the 480V is high current, and worse if the 24v circuits feed a high impedance (i.e. the input to a drive).
The result will be some unwanted noise on the input to the drive. Although the drive has probably been designed to reject a large amount of noise, if it does cause a problem, imagine how hard it would be to troubleshoot or fix later.
Steve
Even if it is allowed by the code, many industrial electricians and engineers make it a point to keep the 24 volt circuits separate from 120V to prevent problems with noise.
Imagine the capacitive and inductive coupling between the wires since they are bundled together so close. Its even worse if they run a long distance, worse for 480V than 120V, worse if the 480V is high current, and worse if the 24v circuits feed a high impedance (i.e. the input to a drive).
The result will be some unwanted noise on the input to the drive. Although the drive has probably been designed to reject a large amount of noise, if it does cause a problem, imagine how hard it would be to troubleshoot or fix later.
Steve
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