Control Panel wire

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mcs

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Have a current project that requires the use of 3/0 AWG for 480V power distribution. I haven't built a panel using this size wire and bend radius is a concern. I was looking into using a high flex wire, but after receiving a sample, I think THHN may be a better option. THHN holds it's shape better after bending. Also leaning towards THHN after reading some posts requiring crimp lugs specifically made for fine stranded cable.
While on the subject of wire, also interested what type wire most panel shops use for:
1. 480V distribution
2. 24VDC control
3. PLC I/O logic
We currently use THHN for 480/240/120VAC, UL1007 or TFFN for 24VDC logic and curious what others commonly use.
Any input is greatly appreciated.
 
For the newer (smaller) PLC's I am using 18awg MTW to go to the IO cards, When my IO leaves the panel I run 16awg MTW in conduit out to inputs and outputs.

I use MTW that has no clear covering over the wire insulation (it may all be this way). The insulation tends to be a little thicker that is why I don't run the 16 awg to the input cards. I always go to terminal blocks from the I/O card.
 
I used THHN for power wiring for a long time, until I discovered Flexible Insulated Bus. It's a lot more expensive from a conductor cost standpoint, but that is more than made up for in reduced assembly time and the ability to make tight bends and reduce panel space. The thing is, it is a "UL Recognized" product, not UL listed, so if you are a UL panel shop that means you have to add it to your procedure, which also costs money (and time).

http://www.erico.com/products/EriflexFlexibles.asp

For control wiring, I used MTW also. Sometimes on specs I was required to use SIS, you want to avoid those jobs, it's a PITA.
 
Jraef said:
I used THHN for power wiring for a long time, until I discovered Flexible Insulated Bus. It's a lot more expensive from a conductor cost standpoint, but that is more than made up for in reduced assembly time and the ability to make tight bends and reduce panel space. The thing is, it is a "UL Recognized" product, not UL listed, so if you are a UL panel shop that means you have to add it to your procedure, which also costs money (and time).

http://www.erico.com/products/EriflexFlexibles.asp

For control wiring, I used MTW also. Sometimes on specs I was required to use SIS, you want to avoid those jobs, it's a PITA.
Click to expand...

Actually, if you use table 28 ampacities, you can use the erico flexible bus w/o a procedure change as it is also recognized as AWM. the procedure change is required to use the expanded ampacities Erico claims byond table 28.
 
travish said:
For the newer (smaller) PLC's I am using 18awg MTW to go to the IO cards, When my IO leaves the panel I run 16awg MTW in conduit out to inputs and outputs.

I use MTW that has no clear covering over the wire insulation (it may all be this way). The insulation tends to be a little thicker that is why I don't run the 16 awg to the input cards. I always go to terminal blocks from the I/O card.
Click to expand...

what size OCPD are you using to protect that 18 awg wire?

mtw comes in a couple different flavors, although it all seems to be 105C AWM dual rated these days.

the transparent coating is found on THHN to make it easier to pull in conduit.
 
Thank you all for the response.

We used MTW for DC control circuits, then changed to UL1007 because it's easier to work with and takes up less space. And as we all know, panel space is usually at a premiun, especially if the mechanical designers get any input. UL1007 is rated for 300V, but when DC control must run with 480V, we use TFFN.

I did find the Flexi-Bus that Jraef also posted and think it'll be a great alternative to standard wire. The price of the busbar isn't too bad, but the tooling price is very high. Is it really necessary, especially the jig for drilling?

Bob referenced Table 28 in regards to ampacity. Is that a UL508 table?
 
mcs said:
Thank you all for the response.

We used MTW for DC control circuits, then changed to UL1007 because it's easier to work with and takes up less space. And as we all know, panel space is usually at a premiun, especially if the mechanical designers get any input. UL1007 is rated for 300V, but when DC control must run with 480V, we use TFFN.

I did find the Flexi-Bus that Jraef also posted and think it'll be a great alternative to standard wire. The price of the busbar isn't too bad, but the tooling price is very high. Is it really necessary, especially the jig for drilling?

Bob referenced Table 28 in regards to ampacity. Is that a UL508 table?
Click to expand...

Table 28 correlates cross sectional area of the conductors to allowed ampacity in UL508a.

BTW, UL508 is not the same thing as UL508a.
 
mcs said:
...
I did find the Flexi-Bus that Jraef also posted and think it'll be a great alternative to standard wire. The price of the busbar isn't too bad, but the tooling price is very high. Is it really necessary, especially the jig for drilling?...
Click to expand...
I used a vice... :roll: We adapted a vice to have smooth jaws so as the not impart the cross hatch pattern onto the exposed plates. We welded some smooth angle iron into the jaws, which also raised the jaw lip up a little so that you can make tight right angle bends by pounding it over with a leaded plastic mallet (rubber was too soft). By the way, drill after bending, and leave a little extra to cut off straight afterward, the plates move and stretch. If you do a lot of work though, you will want to buy the hole punch, it's much much faster and cleaner.
 
Jraef, thank you for the tips in regards to the bus. I have a sample coming today to experiment with. Makes sense drilling after bending. The Erico rep said a uni-bit will work well for the hole. I'm sure we can make up a clamp to hold the laminates while drilling.

petersonra said:
Is UL1007 listed in the table of stuff you are allowed to use in a 508a panel?
Click to expand...

I don't have the UL508a standard yet and was wondering if anyone knew if UL1007 is acceptable in industrial control panels? I plan on taking the seminar in Nov 2012, when it comes to town, which includes a copy. Have seen UL1007 used extensively in other machine tools, eg: Makino. Obviously we are not a UL508a shop, but want to follow it and NFPA79 as close as possible, so when the time comes, we can get certified as painlessly as possible.

Thanks again for your responses!
 
It appears at least some of it (UL1007) is also rated as AWM which is allowed, but the insulation is only rated at 300V. It would have to be physically seperated from any 480V wiring.
 
Last edited:
You may find that having a copy of NFPA79, Electrical Standard for Industrial Machinery may be a good resource.
It appears as though there are many that are not familiar with this document this is the table of contence for it:

http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=79#
NFPA? 79 Electrical Standard for Industrial Machinery 2012 Edition

Chapter 1 Administration
1.1 Scope
1.2 Purpose
1.3 Application
1.4 Specific Provisions Other Than NFPA 79
1.5 Specific Provisions Not Made in Relation to NFPA 70
1.6 State of the Art
Chapter 2 Referenced Publications
2.1 General
2.2 NFPA Publications
2.3 Other Publications
2.4 References for Extracts in Mandatory Sections
Chapter 3 Definitions
3.1 General
3.2 NFPA Official Definitions
3.3 General Definitions
Chapter 4 General Operating Conditions
4.1 General Considerations
4.2 Electrical Components and Devices
4.3 Electrical Supply
4.4 Physical Environment and Operating Conditions
4.5 Transportation and Storage
4.6 Provisions for Handling
4.7 Installation and Operating Conditions
4.8 Available Fault Current
Chapter 5 Incoming Supply Circuit Conductor Terminations and Devices for Disconnecting and Removing Power
5.1 Incoming Supply Circuit Conductor Terminations
5.2 Grounding Terminal
5.3 Supply Circuit Disconnecting (Isolating) Means
5.4 Means for Removal of Power for Prevention of Unexpected Start-Up
5.5 Devices for Disconnecting (Isolating) Electrical Equipment
Chapter 6 Protection from Electrical Hazards
6.1 General
6.2 Protection Against Direct Contact
6.3 Protection Against Electric Shock from Indirect Contact (Fault Conditions)
6.4 Protection by the Use of Protective Extra Low Voltage (PELV)
6.5 Protection Against Residual Voltages
6.6 Protection Against Arc Flash
Chapter 7 Protection of Equipment
7.1 General
7.2 Overcurrent Protection
7.3 Overload Protection of Motors
7.4 Abnormal Temperature Protection
7.5 Protection Against Supply Interruption or Voltage Reduction and Subsequent Restoration
7.6 Overspeed Protection
7.7 Phase Sequence Protection
7.8 Protection Against Overvoltages Due to Lightning and Switching Surges
7.9 Power Factor Correction Capacitors
Chapter 8 Grounding
8.1 General
8.2 Equipment Grounding (Protective Bonding) Circuit
8.3 Control Circuits
8.4 Lighting Circuits
Chapter 9 Control Circuits and Control Functions
9.1 Control Circuits
9.2 Control Functions
9.3 Protective Interlocks
9.4 Control Functions in the Event of Failure
Chapter 10 Operator Interface and Control Devices
10.1 General
10.2 Pushbutton Actuators and Color Graphic Interface Devices
10.3 Indicator Lights and Icons of Color Graphic Interface Devices
10.4 Illuminated Pushbuttons
10.5 Rotary Control Devices
10.6 Start Devices
10.7 Devices for Stop and Emergency Stop
10.8 Devices for Emergency Switching Off
10.9 Displays
Chapter 11 Control Equipment: Location, Mounting, and Enclosures
11.1 General Requirements
11.2 Location and Mounting
11.3 Degrees of Protection
11.4 Enclosures, Doors, and Openings
11.5 Spaces Around Control Cabinets and Compartments
Chapter 12 Conductors, Cables, and Flexible Cords
12.1 General Requirements
12.2 Conductors
12.3 Insulation
12.4 Wire Markings
12.5 Conductor Ampacity
12.6 Conductor Sizing
12.7 Conductors and Cables Used for Flexing Applications
12.8 Cords
12.9 Special Cables and Conductors.
Chapter 13 Wiring Practices
13.1 Connections and Routing
13.2 Identification of Conductors
13.3 Wiring Inside Enclosures
13.4 Wiring Outside Enclosures
13.5 Raceways (Ducts), Support Systems (Cable Supports), Connection Boxes, and Other Boxes
Chapter 14 Electric Motors and Associated Equipment
14.1 General Requirements
14.2 Reserved
14.3 Motor Dimensions
14.4 Motor Mounting and Compartments
14.5 Criteria for Selection
14.6 Protective Devices for Mechanical Brakes
14.7 Direction Arrow
14.8 Marking on Motors
Chapter 15 Accessories and Lighting
15.1 Accessories
15.2 Local Lighting of the Machine and Equipment
Chapter 16 Marking and Safety Signs
16.1 General
16.2 Safety Signs for Electrical Enclosures
16.3 Function Identification
16.4 Machine Nameplate Data
16.5 Equipment Marking and Identification
Chapter 17 Technical Documentation
17.1 General
17.2 Information to Be Provided
17.3 Requirements Applicable to All Documentation
17.4 Basic Information
17.5 Installation Diagram
17.6 Block (System) Diagrams and Function Diagrams
17.7 Circuit Diagrams
17.8 Operating Manual
17.9 Maintenance Manual
17.10 Parts List
Chapter 18 Testing and Verification
18.1 General
18.2 Continuity of the Equipment Grounding (Protective Bonding) Circuit
18.3 Insulation Resistance Tests
18.4 Voltage Tests
18.5 Protection Against Residual Voltages
18.6 Functional Tests
18.7 Retesting
Chapter 19 Servo Drives and Motors
19.1 Overload Protection for Servo Motors
19.2 Motor Overtemperature Protection
19.3 Servo Drive System Conductors.
19.4 Contactor
19.5 Cable Shield
Annex A Explanatory Material
Annex B Inquiry Form for the Electrical Equipment of Machines
Annex C Examples of Industrial Machines Covered by NFPA 79
Annex D Technical Documentation
Annex E Device and Component Designations
Annex F Electrical Enclosure Ratings: Type-Rating Versus IP-Rating
Annex G Kilowatt Outputs with Horsepower Equivalents
Annex H Minimizing the Probability of Control Function Failure
Annex I AWG Conductor Cross-Reference Table.
Annex J Informational References
Index
 
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