SCCR of AC Disconnect

[andrew.tkelly]

Hi,

The AHJ wants me to provide AIC/SCCR ratings of panels, disconnects, and switchboards. While I understand what these values mean, I think I am missing something w/ regards to the ratings of a disconnect.

I am using an unfusible Square D AC disconnect, and its spec sheet says the following:

"Up to 100 kA SCCR, utilizing appropriately rated Class R Class J or Class T fuses or fuse kit"

However, I am using the unfusible version. I am not really sure what the SCCR value would be in this case. Can someone help shine some light on this?

Thanks!

Andy

 

[dkidd]

See http://forums.mikeholt.com/showthread.php?t=187907

 

[petersonra]

Hi,

The AHJ wants me to provide AIC/SCCR ratings of panels, disconnects, and switchboards. While I understand what these values mean, I think I am missing something w/ regards to the ratings of a disconnect.

I am using an unfusible Square D AC disconnect, and its spec sheet says the following:

"Up to 100 kA SCCR, utilizing appropriately rated Class R Class J or Class T fuses or fuse kit"

However, I am using the unfusible version. I am not really sure what the SCCR value would be in this case. Can someone help shine some light on this?

Thanks!

Andy

generally, the SCCR would be 5 kA. you might find a few that are rated for 10 kA, but I have never seen any. I actually saw some that AB says were only good for 3 kA, which I thought was not even possible.

Interestingly, this is what Square D says about it.

https://www.schneider-electric.us/en/faqs/FA87350/

What is the Short Circuit Current Rating(or SCCR) of the Heavy Duty Safety Switches?
Issue:
Product Design Features

Product Line:
Heavy Duty Safety Switches

Environment:
Application

Cause:
Voltage system Short Circuit Current Rating(SCCR)

Resolution:
FOR AC VOLTAGE SYSTEMS ONLY.
The Short Circuit Current Rating(or SCCR) for the Heavy Duty safety switches is dependent upon the type of fuse used either inside the switch(Fusible) OR protecting the switch upstream(Non-Fusible).
1) For Fusible Safety Switches, using Class H or K fuses, the SCCR is 10,000 A. MAX. or when using Class R, J, T or L fuses, the SCCR is 200,000 A. MAX.
NOTE: SEE FAQ For Particular Switch Catalog number to know what Class of fuse the switch will accept.

2) Non-Fusible Heavy Duty Safety Switches do NOT provide any overcurrent protection, therefore the non-fusible heavy duty safety switches alone do NOT provide any SCCR, it MUST be protected upstream by the correct Fuse Class or a circuit breaker.
NOTE: there are limitations of the SCCRs for use with circuit breakers being used in conjunction with Non-Fusible switches. See switch wiring diagram, 2D CAD drawing of the catalog number or the current on-line digest for the ratings with circuit breakers.

FOR DC VOLTAGES SYSTEMS, THE SCCR IS LIMITED TO 10k A MAXIMUM.

if it is part of a Ul508a panel, I think you can still call it 5kA.

 

[tw1156]

Hi,

The AHJ wants me to provide AIC/SCCR ratings of panels, disconnects, and switchboards. While I understand what these values mean, I think I am missing something w/ regards to the ratings of a disconnect.

I am using an unfusible Square D AC disconnect, and its spec sheet says the following:

"Up to 100 kA SCCR, utilizing appropriately rated Class R Class J or Class T fuses or fuse kit"

However, I am using the unfusible version. I am not really sure what the SCCR value would be in this case. Can someone help shine some light on this?

Thanks!

Andy

The other part of this is to ensure that the AC Manufacturer has a SCCR for their equipment which the inspector can also request the available fault current at that location, at least per the 2017 code; 2017 NEC expanded greatly on requiring this and we've seen a slow start from manufacturers adopting this.

 

[pv_n00b]

It's in the digest, page depends on which switch you are using; http://download.schneider-electric....=8449353561&p_File_Name=0100CT1501_SEC-03.pdf

Generally 10kA with any type of upstream OCPD and using series rating it can go up from there.

 

[kwired]

Hi,

The AHJ wants me to provide AIC/SCCR ratings of panels, disconnects, and switchboards. While I understand what these values mean, I think I am missing something w/ regards to the ratings of a disconnect.

I am using an unfusible Square D AC disconnect, and its spec sheet says the following:

"Up to 100 kA SCCR, utilizing appropriately rated Class R Class J or Class T fuses or fuse kit"

However, I am using the unfusible version. I am not really sure what the SCCR value would be in this case. Can someone help shine some light on this?

Thanks!

Andy

That spec sheet applies to both fused and unfused safety switches. If there is appropriate fuse upstream of an unfused switch, it can be series rated up to 100kA, otherwise default rating is 10kA for Square D's heavy duty safety switches.