SCCR by UL508A Supplement SB

[DAB41162]

Hello,

I'm working on establishing the SCCR rating for a PLC control unit using the UL508A Supplement SB.

The available short circuit at the customer's site is unknown. Should I obtain this before proceeding or continue?

The main breaker in the control unit is a Schneider Electric HJL36080 on a line voltage of 208VAC. The SCCR for this breaker is 100kA @ 240V (per datasheet). Can this 100kA rating be used for the breaker?

The load side of the breaker goes through two contactors with an SCCR of 100kA @ 480V (per UL Certificate). Again, can this 100kA rating be used for the contactors?

Finally, the load side of the contactors goes to a Schneider Electric 9080LBA263106 distribution block. Per the UL certificate, it was tested with a JJL36250 and is rated at 65kA @ 480V. Could there be a rating for this component at 240V?

All of the loads from this block are protected by class CC (200kA @ 600V) fuses in holders rated at 200kA @ 600V.

I was hoping to have a 100kA @ 240V SCCR for the control unit. Should the value be set at 65kA @ 240V?

Thank you.

 

[petersonra]

Hello,

I'm working on establishing the SCCR rating for a PLC control unit using the UL508A Supplement SB.

The available short circuit at the customer's site is unknown. Should I obtain this before proceeding or continue?

The available SCC has no effect on the way the SCCR of the panel is established. The end user needs to specify what the SCCR of the panel needs to be.

The main breaker in the control unit is a Schneider Electric HJL36080 on a line voltage of 208VAC. The SCCR for this breaker is 100kA @ 240V (per datasheet). Can this 100kA rating be used for the breaker?

Breakers do not have a SCCR. They have an AIC rating. If it is being fed with 240V or less then yes.

Having said that, it seems unlikely that a panel with an 80 A main breaker would need a SCCR of 100 kA.

The load side of the breaker goes through two contactors with an SCCR of 100kA @ 480V (per UL Certificate). Again, can this 100kA rating be used for the contactors?

It would be somewhat unusual to find a contactor with a SCCR of 100 kA unless it is a series rating that requires specific OCPD upstream.

Finally, the load side of the contactors goes to a Schneider Electric 9080LBA263106 distribution block. Per the UL certificate, it was tested with a JJL36250 and is rated at 65kA @ 480V. Could there be a rating for this component at 240V?

If it does not specify a rating at 240 V then you would have to use the 480 V rating.

All of the loads from this block are protected by class CC (200kA @ 600V) fuses in holders rated at 200kA @ 600V.

You still have to look at whatever power loads are downstream of these fuses but within the panel. Most likely it will be OK but you need to look. For instance, some SCR controllers are only rated with certain types of fast blow Class J fuses.

I was hoping to have a 100kA @ 240V SCCR for the control unit. Should the value be set at 65kA @ 240V?

Thank you.

The SCCR rating of the panel is the lowest rating for any power device. It is hard to say what the panel rating will be not knowing what is down stream of the Class CC fuses, but the panel rating will not exceed 65 kA.

BTW, my certificate as a manufacturer's technical representative in UL508a expires next month so whatever advice I give is only valid till then.

 

[DAB41162]

Thank you for your input and time.

 

[Jraef]

Worth adding that the contactor rating is likely 10kA, unless series tested and listed with a SPECIFIC upstream protective device. So you will have to go to Schneider to see what possibilities exist for those contactors. If the 100kA listing you mentioned came from them with THAT EXACT breaker, then you are fine.

Likewise with the distribution block. If it is listed in series with the HJL 80A breaker, you are fine. It’s depends on how that listing with the JJL 250 was worded. If it was narrowly specific, you may need to add fuses (most everything that is listed with breakers is also listed with fuses).