THHN wire splices and SCCR

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pisani168

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I have to replace a MCC. Motor feeders are routed through RMC to the motor. The new lineup will have a different elevation pattern because I added some smart features and AF reduction means. That being said, some feeders will be too short.

The fault duty is greater than 10kA so that I cannot use random Joe Blow mechanical splices. Are crimped butt splices considered a conductor extension like lugs? In other words!p, are they excluded from short circuit current testing per UL? If so, would this still be considered a ”splice” and need to be accessible?

Need to weigh the cost of pulling new wire.
 
pisani168 said:
I have to replace a MCC. Motor feeders are routed through RMC to the motor. The new lineup will have a different elevation pattern because I added some smart features and AF reduction means. That being said, some feeders will be too short.

The fault duty is greater than 10kA so that I cannot use random Joe Blow mechanical splices. Are crimped butt splices considered a conductor extension like lugs? In other words!p, are they excluded from short circuit current testing per UL? If so, would this still be considered a ”splice” and need to be accessible?

Need to weigh the cost of pulling new wire.
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I think that is an urban legend. I have heard it before but no one can seem to find documentation requiring it.
 
This is not a legend. It can be found in UL table SB4. All termination blocks regardless of how many ports they have are rated 10kA unless the OEM provides a “high fault rating” which is UL language for a SCCR > than the minimum requirement of 10kA.
A mechanical wire splice with a bolt or screw is considered a terminal block.
 
pisani168 said:
A mechanical wire splice with a bolt or screw is considered a terminal block.
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No it is not. The SCCR applies to power distribution blocks. Not sure if a "terminal block" is synonymous with a "power distribution block", but regardless, the SCCR requirement/restriction does not apply to wire connectors. See post #36 here:

Insulated multi tap connectors

http://www.ihiconnectors.com/SCCR-UL508.htm Interesting find, but UL508 is for control panels, so again it looks to me like this only applies to equipment used in a manufactured assembly. Which would make sense because we already know those need an SCCR. And those also all seem to be mounted...
forums.mikeholt.com
 
But no, an in-line crimp splice would not be considered a power terminal that needs to be included in the SCCR. It is not a mechanical device that needs to be braced for having to withstand the mechanical forces of a fault (other than the wire itself needing to be secured).
 
Are you thinking Polaris type connectors or a split bolt and a big ol' wad of tape? If so, that would be correct, because they too are not mounted to anything other than the wire itself. But if the splice is done with a terminal block type of device that is mounted down, then it does fall into being considered in the SCCR.
 
electrofelon said:
No it is not. The SCCR applies to power distribution blocks. Not sure if a "terminal block" is synonymous with a "power distribution block", but regardless, the SCCR requirement/restriction does not apply to wire connectors. See post #36 here:

Insulated multi tap connectors

http://www.ihiconnectors.com/SCCR-UL508.htm Interesting find, but UL508 is for control panels, so again it looks to me like this only applies to equipment used in a manufactured assembly. Which would make sense because we already know those need an SCCR. And those also all seem to be mounted...
forums.mikeholt.com
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NEC2020 requires SE splices to be rated for for this application because of the high fault currents. An insulated dual connector must have a SCCR.
Jraef said:
But no, an in-line crimp splice would not be considered a power terminal that needs to be included in the SCCR. It is not a mechanical device that needs to be braced for having to withstand the mechanical forces of a fault (other than the wire itself needing to be secured).
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I agree. Crimped connectors are excluded from SCCR. This is particularly mentioned in UL508A. Thanks for the reassurance for in line crimps.
 
I’ll call my buddy on the UL508A committee later on and ask him. Will share his answer.

We run wire in conduit because the electro magnetic forces would whip wires around in case of a fault but then we allow a screw type terminal splice floating with tape in a box or wire way? That will be the weakest spot during a fault and potentially be ripped apart. That’s my thought and not a UL tested fact.
NEC 2020 considered this fact and only allows service entry splices when the splice kit is rated for this. And he reason why it needs to be rated is because of the high fault currents. Makes sense to me considering that a lot of SE are still OH and splices at the weather cap.
 
If using power distribution blocks for splices/taps of service conductors they must be listed and marked for use on service conductors. And now in the 2020 edition as of 1/1/2023 this will apply to all pressure type splices such as Polaris connectors. See 230.46 NEC 2020.
 
Keep in mind UL508A only applies to UL508A panels. It might provide some guidance for other situations but it does not actually apply except within a listed UL 508A panel.
 
pisani168 said:
NEC2020 requires SE splices to be rated for for this application because of the high fault currents. An insulated dual connector must have a SCCR.
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Not really. I've got to be justice Scalia again and ask where on earth are you seeing that wording??....230.46 requires an SEC splice to be marked "suitable for use on the line side of the service equipment", and that is post dated until 2023. I am not seeing anything in there about SCCR. I don't know if the standard has been fully developed yet.
 
Here is the answer from UL:

if the splice is listed under UL486 no SCCR is required. If it’s listed under UL1059 or UL1953 the min must be 10kA.
I guess the lessons is to pick splices based on the UL standard it’s listed under.
 
petersonra said:
Was there ever a history of a safety issue being caused by a short circuit that exceeded the sccr of the equipment? Ever?
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Yes. For sure in commercial and industrial. I know of two fatalities.
You can go on YouTube and check out some overdutied equipment videos during faults.

in residential it’s unlikely due to the size of the transformers. However, sometimes you have bigger sized transformers feeding multiple homes or units. That is where it gets dangerous because the let thru current of the transformer may easily exceed 10,000A.
 
pisani168 said:
Yes. For sure in commercial and industrial. I know of two fatalities.
You can go on YouTube and check out some overdutied equipment videos during faults.

in residential it’s unlikely due to the size of the transformers. However, sometimes you have bigger sized transformers feeding multiple homes or units. That is where it gets dangerous because the let thru current of the transformer may easily exceed 10,000A.
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I am not talking about arc flash or problems due to OCPD that could not interrupt the available SCC. Solely about SCCR. I don't think it has ever happened.
 
pisani168 said:
Yes. For sure in commercial and industrial. I know of two fatalities.
You can go on YouTube and check out some overdutied equipment videos during faults.

in residential it’s unlikely due to the size of the transformers. However, sometimes you have bigger sized transformers feeding multiple homes or units. That is where it gets dangerous because the let thru current of the transformer may easily exceed 10,000A.
Click to expand...
I agree. They network transformers in dense urban areas. Explosions can happen. And many transformers are fused really high or not at all for sake of service continuity. Line side service equipment and devices should have a very high rating.

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