UL 508A Table SB4.2

[BKearney]

I want to get my boxes up to 100kA SCCR as a standard...

Is the omission of class CC fuses below 15 amp in table SB 4.2 to be interpreted as me not being able to use class CC fuses below 15 amps even though the class CC fuses I use from Ferraz Shawmut are all 100kA SCCR regardless of fuse amp size?

As I read SB4.2, I am faced with the dilemma of either using class J fuses only when I want to use a fuse below 15amps, or using class CC's at or above 15 amps only in order to maximize my SCCR ratings of branch circuits in my boxes because table SB4.2 does not list any class CC fuses less than 15 amp.

Thanks in advance for any input!

 

[BKearney]

Since I have not had anyone take a stab at this yet, let me say it a different way...

I can purchase class CC fusees and fuse holders that have a 200kA SCCR with fuse sizes ranged from 1/4A to 30A.

Why does 508a only show 15A, 20A and 30A class CC fuses in table SB4.2?

Is that an omission in table SB4.2, or are they saying if I use class CC fuses I cannot use lower than 15A rating?

I guess since I am restricted to 14awg wires anyway I can go to 15A class CC fuses regardless of what is on the branch but it irks me I can't use smaller class CC fuses if I wanted to, according to table SB4.2.

We are trying to ask UL, but that's like wathcing grass grow...

Thanks for any input...

 

[richwaskowitz]

It seems to me that the Fuse Rating Amperes column is referring to UP TO 15, 20, 30 amps etc.

 

[BKearney]

I agree...

We have not heard back from UL, but other sources who are 508A panel shops say the same thing, that it is just an upper limit and you can use lower values.

The caution would be, if the manufacturer has a device you are using listed with a class J fuse or a class J fuse of a certain size to get the SCCR rating they list, then you must stick with that combination to get that SCCR rating. For example, some variable frequency drive manufacturers have thier drive SCCR ratings listed using a specific fuse class, like class J, so you need to use class J with that drive and not class CC.

Thanks for the feedback!