DLO Cable Support Requirements

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FaradayFF

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Hey Guys,
Is there an industry standard or guidance on supporting DLO type cable for horizontal runs(run exposed, not in cable tray)? All I've found in NEC is that cable routed in cable tray and TC type cable support requirements, but not for the DLO cable type.
Any advice would be appreciated.
Thanks,
EE
 
With an allowable type cable (Dual Rated) I would think 398.30 would apply
 
augie47 said:
With an allowable type cable (Dual Rated) I would think 398.30 would apply
Click to expand...
398.1 Scope. This article covers the use, installation, and
construction specifications of open wiring on insulators.
398.2 Definition.
Open Wiring on Insulators. An exposed wiring method using
cleats, knobs, tubes, and flexible tubing for the protection and
support of single insulated conductors run in or on buildings.
Click to expand...

This does not sound like anything anyone would actually do these days. In any case if you are not using cleats, knobs, tubes or flexible tubing for support it does not seem possible that this article could apply given the definition.
 
It is still installed in some of our "heavy industry" applications.
 
FaradayFF said:
Hey Guys,
Is there an industry standard or guidance on supporting DLO type cable for horizontal runs(run exposed, not in cable tray)? All I've found in NEC is that cable routed in cable tray and TC type cable support requirements, but not for the DLO cable type.
Any advice would be appreciated.
Thanks,
EE
Click to expand...

Out of curiosity what is the application? Battery room or something?
 
Usually DC equipment that violates bending space requirements such as that designed and built by GE uses DLO. It’s pretty common in DC applications.

It is dual rated as RHH/RHW-2 which is an allowable NEC type, 90 C wet or dry. It can be run in trays if it is listed for TC use on the jacket. But it is not and never has been rated for exposed runs outside of some kind of raceway. It also requires special lugs for fine strand and due to the nonstandard diameters make sure you get the right lugs. A 500 MCM lug does not go on 535 MCM DLO.

If you look at the use cases though lots of people violate this a lot but it’s not to Code. It is a NEMA cable rating so NEC is highly biased against it. It is intended mostly for mobile uses which fall outside NEC scope but the DC guys tend to ignore that. I’ve seen SHD-GC and drill rig cable types drift over into NEC land too. I don’t honestly see any NEC cable types hold up to years of being drug through crushed rocky mud and gravel. They treat every cable as something to be boxed in.

A better choice is type TC-ER or in smaller sizes type MC. Both are exposed run rated so they can run in or out of trays if properly supported, they are available in fine strand if you shop around (see Service Wire Company, Houston Wire, Amercable/Nexans), but you have the choice to just use coarse strand standard type B construction. You can get “VFD” cable with a 2 kV rating this way. The only thing you give up is the tinned coating that is highly overrated.
 
Todd0x1 said:
Out of curiosity what is the application? Battery room or something?
Click to expand...
I work at a fiberglass insulation mfr. We use the dual rated DLO / RHW-2 in a 535mcm size. We use 14 cables per phase to connect the power supply to the copper buss (about 5 feet) And from the buss to the electrode arm (3 inch gun drilled copper shaft for water cooling. The electrode is a 8 in diameter molybdenum cylinder 10 inches long. The cable between the buss and the electrode arm needs to be flexible so that the electrode can be raised, tilted, and swung out of the glass pool every 45 days because the electrode is consumed.
 
milldrone said:
I work at a fiberglass insulation mfr. We use the dual rated DLO / RHW-2 in a 535mcm size. We use 14 cables per phase to connect the power supply to the copper buss (about 5 feet) And from the buss to the electrode arm (3 inch gun drilled copper shaft for water cooling. The electrode is a 8 in diameter molybdenum cylinder 10 inches long. The cable between the buss and the electrode arm needs to be flexible so that the electrode can be raised, tilted, and swung out of the glass pool every 45 days because the electrode is consumed.
Click to expand...

So that is DLO substituted for a flexible cable type. It will never be Code. DLO is raceway bound even as RHW. So live with it or find another cable type. Other than considering a high flex/high strand “welding” style cable more intended as a flexible cord type there isn’t much to improve on this use. It’s just an area where NEC falls down. You are definitely doing an “off book” application but hard to argue against how you are doing it.
 
paulengr said:
So that is DLO substituted for a flexible cable type. It will never be Code. DLO is raceway bound even as RHW. So live with it or find another cable type. Other than considering a high flex/high strand “welding” style cable more intended as a flexible cord type there isn’t much to improve on this use. It’s just an area where NEC falls down. You are definitely doing an “off book” application but hard to argue against how you are doing it.
Click to expand...

That seems like it should be Type W which is the proper single conductor extra hard usage portable cord, they make it in 500mcm.
 
paulengr said:
So that is DLO substituted for a flexible cable type. It will never be Code. DLO is raceway bound even as RHW. So live with it or find another cable type. Other than considering a high flex/high strand “welding” style cable more intended as a flexible cord type there isn’t much to improve on this use. It’s just an area where NEC falls down. You are definitely doing an “off book” application but hard to argue against how you are doing it.
Click to expand...
Article 398 permits any conductor found in Article 310 to be installed as open wiring on insulators. RHW is found in Article 310, and therefore a conductor dual marked DLO/RHW is permitted for that application
 
In an application like this, does the NEC even apply?
There's probably a fair amount of engineering supervision.
Most likely only qualified workers touch the installation.
If the arc/furnace is after a huge transformer, it could be considered utilization equipment.

(I'm not saying that safe practices shouldn't apply.)
 
paulengr said:
Usually DC equipment that violates bending space requirements such as that designed and built by GE uses DLO. It’s pretty common in DC applications.

It is dual rated as RHH/RHW-2 which is an allowable NEC type, 90 C wet or dry. It can be run in trays if it is listed for TC use on the jacket. But it is not and never has been rated for exposed runs outside of some kind of raceway. It also requires special lugs for fine strand and due to the nonstandard diameters make sure you get the right lugs. A 500 MCM lug does not go on 535 MCM DLO.

If you look at the use cases though lots of people violate this a lot but it’s not to Code. It is a NEMA cable rating so NEC is highly biased against it. It is intended mostly for mobile uses which fall outside NEC scope but the DC guys tend to ignore that. I’ve seen SHD-GC and drill rig cable types drift over into NEC land too. I don’t honestly see any NEC cable types hold up to years of being drug through crushed rocky mud and gravel. They treat every cable as something to be boxed in.

A better choice is type TC-ER or in smaller sizes type MC. Both are exposed run rated so they can run in or out of trays if properly supported, they are available in fine strand if you shop around (see Service Wire Company, Houston Wire, Amercable/Nexans), but you have the choice to just use coarse strand standard type B construction. You can get “VFD” cable with a 2 kV rating this way. The only thing you give up is the tinned coating that is highly overrated.
Click to expand...
I notice in the DLO cable data sheet that the same minimum bending radius as a regular cable of the same size and insulation applies to the DLO cable. In reality, since the DLO type is more flexible(utilizes hundreds of strands), isn't this bending radius requirement violated on a regular basis when DLO cable is installed?
Is there a general rule of thumb(multiplier) when it comes to the minimum bending radius recommended for DLO?

Thank you,
EE
 
All bending radius information for single conductors less than 1000 volts comes from the conductor manufacturers and most of them are written as recommendations and not as a mandatory requirement.
 
FaradayFF said:
I notice in the DLO cable data sheet that the same minimum bending radius as a regular cable of the same size and insulation applies to the DLO cable. In reality, since the DLO type is more flexible(utilizes hundreds of strands), isn't this bending radius requirement violated on a regular basis when DLO cable is installed?
Is there a general rule of thumb(multiplier) when it comes to the minimum bending radius recommended for DLO?

Thank you,
EE
Click to expand...

NEMA WC 70 dictates a minimum radius of 4xOD up to 1” OD where ICEA normally specifies 8xOD for a 2 kV cable and 5xOD for 600 V cables. DC voltages naturally tend to be higher since the output of a full wave bridge is 145% of AC RMS so a 480 V system may require a 2 kV cable. In many DC terminations you do not have the space for proper bends if the bend radius doubles when using a normal unshielded cable.
 
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