480V Receptacles Cord protection

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Electrobe

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AT an industrial site they have 60Amp 480VAC receptacles scattered around the site that they use for temporary cord connected equipment such as welders, saws, and misc. other equipment. How should the cord be sized for feeding the temporary equipment? Does it need to be sized for 60Amps or is there some rule that allows smaller 480VAC equipment to be connected with smaller cord? (i.e. 20amp equipment to use #10 cord but be connected to a 60amp plug protected by 60AMP fuses)

Thanks in advance.
 
Electrobe said:
AT an industrial site they have 60Amp 480VAC receptacles scattered around the site that they use for temporary cord connected equipment such as welders, saws, and misc. other equipment. How should the cord be sized for feeding the temporary equipment? Does it need to be sized for 60Amps or is there some rule that allows smaller 480VAC equipment to be connected with smaller cord? (i.e. 20amp equipment to use #10 cord but be connected to a 60amp plug protected by 60AMP fuses)

Thanks in advance.
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That would all depend on what was on the receiving end of the smaller cord that is plugged into the 60 Amp Connector.

JAP>
 
jap said:
That would all depend on what was on the receiving end of the smaller cord that is plugged into the 60 Amp Connector.

JAP>
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Use as an example a 3Hp, 480v saw with all the proper motor protection located on the equipment.

Thanks
 
Electrobe said:
AT an industrial site they have 60Amp 480VAC receptacles scattered around the site that they use for temporary cord connected equipment such as welders, saws, and misc. other equipment. How should the cord be sized for feeding the temporary equipment? Does it need to be sized for 60Amps or is there some rule that allows smaller 480VAC equipment to be connected with smaller cord? (i.e. 20amp equipment to use #10 cord but be connected to a 60amp plug protected by 60AMP fuses)

Thanks in advance.
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I don't know your rules/code but I would rate it for 60A. Who knows who will plug it in to the receptacle and whether they would know what the rating of the equipment being powered is?
 
Besoeker said:
I don't know your rules/code but I would rate it for 60A. Who knows who will plug it in to the receptacle and whether they would know what the rating of the equipment being powered is?
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I think the question is about the cord that is plugged into the 60 amp receptacle, not the wire supplying the receptacle.
 
Electrobe said:
How should the cord be sized for feeding the temporary equipment? Does it need to be sized for 60Amps or is there some rule that allows smaller 480VAC equipment to be connected with smaller cord?
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Once you're outside of any specific rules (motors, welders, etc), I think you're back to 240.5(A) which wouldn't otherwise allow a 12g conductor on a 60a breaker. OTOH, I'm not sure how 240.10 would apply (Supplementary Overcurrent Protection).
 
zbang said:
Once you're outside of any specific rules (motors, welders, etc), I think you're back to 240.5(A) which wouldn't otherwise allow a 12g conductor on a 60a breaker. OTOH, I'm not sure how 240.10 would apply (Supplementary Overcurrent Protection).
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It looks like table 400.5(A)(1) says a 3/C #12AWG SO cord must be protected for 20Amps. Where did you find that it is allowed to be connected to a 60amp breaker?

Thanks
 
If there is overcurrent protection at the end of the 20 amp rated cord, I don't see this as being any different than a tap.

But, I would have to read up on the rules seeing as how this is a cord type installation.


JAP>
 
jap said:
If there is overcurrent protection at the end of the 20 amp rated cord, I don't see this as being any different than a tap.

But, I would have to read up on the rules seeing as how this is a cord type installation.


JAP>
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I would agree this sounds just like a tap but all the tap rules require the conductors to be protected by a raceway or be within the same enclosure. Not sure a cord would qualify as being protected?

Thanks
 
In the analogous situation of 120V cord and plug connected appliances, connected to 15A or 20A circuits, the cord generally has much lower ampacity than the circuit conductors, eg. 18 AWG appliance cord for a clock or the like.

As I understand this, this is _not_ an NEC issue, but rather something set by the manufacturer or UL.

I presume that for any sort of manufactured 480V device which might be plug connected, there will be specifications for the maximum OCPD and for the ampacity of the cord, or some information available from the manufacturer.

I don't know if there is any sort of analogous provision or design process for devices assembled in the field. Clearly it isn't always the case that a cord needs to be protected at its ampacity by the upstream OCPD, but NEC might not have a method to allow the proper selection of such a reduced size cord.

Sometimes just using the full sized conductors is cheaper than the engineering necessary to justify the use of reduced sized conductors.

-Jon
 
Electrobe said:
It looks like table 400.5(A)(1) says a 3/C #12AWG SO cord must be protected for 20Amps. Where did you find that it is allowed to be connected to a 60amp breaker?
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I don't, just the opposite. Unless there are special circumstances like a listed appliance using the supplied cord, etc, you gotta follow Art 400.

Echoing Jon, sometimes it isn't worth the time to find the exception. And sometimes it's worth time/expense to tap the 60A branch circuit and install a 20A breaker/outlet next to the 60A one.
 
zbang said:
I don't, just the opposite. Unless there are special circumstances like a listed appliance using the supplied cord, etc, you gotta follow Art 400.

Echoing Jon, sometimes it isn't worth the time to find the exception. And sometimes it's worth time/expense to tap the 60A branch circuit and install a 20A breaker/outlet next to the 60A one.
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I agree. The site currently uses whatever ampacity cord that is required to operate the equipment and puts a 60Amp plug on the cord to use it everywhere around the site (this could be 3C #12). This seemed wrong to me because the cord is not protected but I was not sure because it is similar to 120V receptacles which are allowed to connect smaller gauge wire to maybe a 20amp circuit. I think I am going to push for making sure the cord is protected by either adding a 20A receptacle with the correct fusing/breaker or using oversized cords unless someone sees another option. I will also review the OSHA codes to see what they may have.

Thanks for the feedback!!
 
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