Thread: Conductor Radius

Think these conductors should possess more radius? Looking a little tight.

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Just my opinion but from the photo it looks OK to me.

It looks tight to me also.

Cable Type Minimum Bending Radius
as a Multiple of Overall Cable Diameter
Single or Multiple Conductor Cables
without Metallic Shielding
8 times the overall cable diameter
Single Conductor Cables
with Shielding
12 times the overall cable diameter
Multiple Conductor Cables with
Individually Shielded Conductors
12 times the individual cable diameter or
7 times the overall cable diameter -- whichever
is greater
Portable (Mining) Cables 6 times for cables rated 5000 volts or less,
8 times for cables rated over 5000 volt
Fiber Optic Cables 10 times overall diameter for multimode cables,
20 times overall diameter for singlemode cables
Interlocked Armor or Corrugated Sheath
(Type MC) Cables
7 times overall cable diameter
To use the table, obtain the required cable diameter from product literature, from the cable
supplier, or by measuring the actual cable. Then multiply that diameter by the appropriate
factor from the table.

Originally Posted by Rick Cantrell

It looks tight to me also.

Cable Type Minimum Bending Radius
as a Multiple of Overall Cable Diameter
Single or Multiple Conductor Cables
without Metallic Shielding
8 times the overall cable diameter
Single Conductor Cables
with Shielding
12 times the overall cable diameter
Multiple Conductor Cables with
Individually Shielded Conductors
12 times the individual cable diameter or
7 times the overall cable diameter -- whichever
is greater
Portable (Mining) Cables 6 times for cables rated 5000 volts or less,
8 times for cables rated over 5000 volt
Fiber Optic Cables 10 times overall diameter for multimode cables,
20 times overall diameter for singlemode cables
Interlocked Armor or Corrugated Sheath
(Type MC) Cables
7 times overall cable diameter
To use the table, obtain the required cable diameter from product literature, from the cable
supplier, or by measuring the actual cable. Then multiply that diameter by the appropriate
factor from the table.

Well done Rick...thanks buddy..

Originally Posted by Rick Cantrell

It looks tight to me also.

Cable Type Minimum Bending Radius
as a Multiple of Overall Cable Diameter
Single or Multiple Conductor Cables
without Metallic Shielding
8 times the overall cable diameter
Single Conductor Cables
with Shielding
12 times the overall cable diameter
Multiple Conductor Cables with
Individually Shielded Conductors
12 times the individual cable diameter or
7 times the overall cable diameter -- whichever
is greater
Portable (Mining) Cables 6 times for cables rated 5000 volts or less,
8 times for cables rated over 5000 volt
Fiber Optic Cables 10 times overall diameter for multimode cables,
20 times overall diameter for singlemode cables
Interlocked Armor or Corrugated Sheath
(Type MC) Cables
7 times overall cable diameter
To use the table, obtain the required cable diameter from product literature, from the cable
supplier, or by measuring the actual cable. Then multiply that diameter by the appropriate
factor from the table.

Do you have a reference for this material and how it applies to the conductors in the photo?

Originally Posted by Robert Meier

Do you have a reference for this material and how it applies to the conductors in the photo?

The document is on my computer at work.
Someone from IN (I think it was Jerry) posted the document here some time ago.

Originally Posted by Rick Cantrell

The document is on my computer at work.
Someone from IN (I think it was Jerry) posted the document here some time ago.

When I look at that list I don't see anything that applies to the photo in the OP.

Originally Posted by Robert Meier

When I look at that list I don't see anything that applies to the photo in the OP.

Yeah, but awful handy to know about the 8 times for 5000 volt cable

Corey

The NEC specifies the bending radius for conductors over 600 volts:
- 300.34 Conductor Bending Radius.
- - The conductor shall not be bent to a radius less than 8 times the overall diameter for nonshielded conductors or 12 times the overall diameter for shielded or lead-covered conductors during or after installation. For multiconductor or multiplexed single-conductor cables having individually shielded conductors, the minimum bending radius is 12 times the diameter of the individually shielded conductors or 7 times the overall diameter, whichever is greater.

The NEC does not specifically specify the bending radius for conductor under 600 volts ... not specifically ... 110.3(B) does in that the conductors themselves are designed for a bending radius based on the diameter of the conductor, and for typical residential installation that bending radius is 4 times the diameter of the conductor, including insulation, i.e., conductor which is 1/2" in size has a minimum bending radius of 2", or a bending diameter of 4".

The above comes from the engineering for the conductors.

The NEC does, in an interpretive way, imply a bending radius in that the NEC specifies wire bending space for various sized conductors in 312.6 Deflection of Conductors. That bending space is approximately based on a radius of 6+/- times the diameter of the conductors (for the conductors I checked - the calculation rounded off to 6).

A 6 times bending space will accommodate a a 4 times bending radius.

in a nut shell you need to use table 312.6A to determine the wire bending space required in that picture.

Like Jerry said there is nothing definitive in the NEC for cables on sytems under 600 Volt. One can write it up but if the equipment meets 312.6A and it is under 600 volts -you have nothing to back your write up.

Originally Posted by ken horak

One can write it up but if the equipment meets 312.6A and it is under 600 volts -you have nothing to back your write up.

"you have nothing to back your write up"

110.3(B) addressed that as the wire is manufactured to a standard which includes the limitations on bending.

Marc,

Add the following link to your (and your other california inspectors) list of favorites, especially quick access and low mem consumption when in the field on wifi/wireless card:

RealRead Viewer : California*Electrical*Code*2010

The above is a link to a NFPA hosted version of the (as ammended by California) of the 2010 California Electrical Code (Title 24, Part 3) which is based upon the 2008 NEC, and is specific to California 2010 edition, eff. Jan 1, 2011, including california ammendments, additions & subtractions.

You will need to have active x/java & cookies enabled and allow opening of new windows/popups. This clickable link above will get you right away into the California specific document without having to sign-in, signup, etc. Its a www "expressway" directly into the 2010 California Electrical Code.

When the oocument loads in the new window (in a reader) click on the table of contents icon at the bottom right - it will pop up yet another window table of contents which is navigatable by article, click on Article 316 and it will advance the reader document to same, you can then read page by page using the page forward and back icons at the bottom of the reader.

I think you'll find the specifics in the Article (which is a short one) on point to the OP in this topic, as well as some of your more recent posts including the cabinet front encounter with a hot conductor you had recently.

HTH.

P.S.
Pay special attention to the cross references within the Article and the footnotes to the table(s).

You will sometimes find specific references for bending radius limitations for specific conductor/cable types under the article pertaining to the wiring method; for example Type NM Cable Article 334 at 334.24. For other wiring methods you should find at/about .24 of the appropriate article if addressed therein.

I believe the table Rick referenced is one often repeated by cable manufacturer's relative to combination of information from both the NEC & the Insulated Cable Engineers Association (ICEA).

Again, HTH.

Thanks for the link HG

Thanks HG, great information.

Marc & Tim,

You are most welcome.

Will you call this out in a report? After reading this thread and looking at it again, IMO there still isn't a problem with the bend radius of the conductor.

Even if it were to comply with NFPA-70, Table 312.6(A), 110.12 requires "workmanlike manner", FPN references NECA 1-2006. NECA 1-2006, 9(c) .."wire and cables shall be installed so as not to damage the insulation or cable sheath..."
From the photo it appears that the cable jacket is damaged from the tight bend.

Originally Posted by Donald Kane

Even if it were to comply with NFPA-70, Table 312.6(A), 110.12 requires "workmanlike manner", FPN references NECA 1-2006. NECA 1-2006, 9(c) .."wire and cables shall be installed so as not to damage the insulation or cable sheath..."
From the photo it appears that the cable jacket is damaged from the tight bend.

IMO the cable is not damaged and workman like manner is so ambiguous that it's almost unenforceable.

Originally Posted by Robert Meier

IMO the cable is not damaged and workman like manner is so ambiguous that it's almost unenforceable.

I agree 110.12 is so broad it is hard to enforce.

The installer also kept the conductor to the farthest point away from the terminal that the enclosure would allow.

The radius isn't what catches my eye in the OP's picture. There is nothing wrong with those bends. That is a new looking can and if it is UL listed then whatever bend you have to make to get the wire into the lugs has been calculated and the space required given within the can. So unless you are second guessing the engineer who designed the can and UL lab that tested it you have nothing to write up.

What does look dangerous to me is the proximity of the wire on the "B" phase that runs directly behind and looks like it is touching the back side of the lug on the "A" phase. Should the insulation get cut by the lug or either one overheat and melt their insulation it would be one hell of a fireworks display. The conductor should have been routed differently!

Lou,
If the supply got so hot as to melt the insulation there would already be big trouble before the arc...

Is it okay that the neutral is wrapped in white hockey tape?

Is this because these wires didnt come in a bigger cable (ie:6/3) and are three separate cables and we need to identify the neutral?

thanx

Originally Posted by Donald Kane

Even if it were to comply with NFPA-70, Table 312.6(A), 110.12 requires "workmanlike manner", FPN references NECA 1-2006. NECA 1-2006, 9(c) .."wire and cables shall be installed so as not to damage the insulation or cable sheath..."
From the photo it appears that the cable jacket is damaged from the tight bend.

The cable appears to be a type that has a nylon covering over the thermoplastic insulation. The two materials have slightly different properties and the nylon will frequently "bunch up" as shown. This does not damage the insulation. The nylon is a pulling aid and it being bunched, scuffed, or even missing, isn't an issue. Some newer and "slicker" types of insulation don't have the nylon covering. This info isn't easy to find and usually requires talking to an engineer at the manufacturer.

Is it okay that the neutral is wrapped in white hockey tape?

Is this because these wires didnt come in a bigger cable (ie:6/3) and are three separate cables and we need to identify the neutral?
As to the "hockey tape", it is common practice to mark individual wires in sizes 4 or larger with coding or marking tape to identify it as a neutral and is permitted by the NEC. A lot of wire is marked this way in sizes 6 and 8. Not permitted by code when individual wires are used but done frequently anyway. A cable containing multiple wires can be marked as needed. Different rules in Canada on some of this stuff.

There are color coding tapes sold for identifying electrical conductors.