- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Has anyone heard of two different types of GEAR being "series rated"? A claim was made by a salesperson for a company that makes MCCs and Switchgear that they must be given the order for both because their MCCs are "series rated" at 100kA with the switchgear and if the user were to buy MCCs from a different mfr, they won't be.
The data sheets for the MCCs clearly state that the MCCs are rated for "only" 65kA. I was not given the one-line diagram yet so I don't know what the actual available fault current is, but I called BS on this just on the general principal. I know what series ratings of circuit breakers and fuses are and how it works, and I know that in the panelboard/load center world the manufacturers series rate their panels for use behind a specific main or up stream feeder breaker used as a to get a higher overall rating. But I also know that to attain that, they must test them in series with very specific components installed and it's a destructive testing process, so it is only done for high volume applications like residential / commercial panels where they sell thousands and thousands of them every year. I've never heard of this concept extending into primary type gear like LV Switchgear feeding LV MCCs.
I'm thinking that the Switchgear might be rated for 100kA even if you only need 65kA because that's getting to be a fairly common general spec now, but I don't think anyone has gone through the extreme expense of series rating an entire MCC lineup so that you can use a 65kA rated MCC in a system capable of 100kA by using the same manufacturer's switchgear in series. My bet is that the MCCs are rated for 65kA because the available fault current is <65kA at the MCC terminals, not because there is any "series rating" with the up stream gear.
But I've been out of the Switchgear business for a decade or more now, so is there something new out there that I'm not aware of?
The data sheets for the MCCs clearly state that the MCCs are rated for "only" 65kA. I was not given the one-line diagram yet so I don't know what the actual available fault current is, but I called BS on this just on the general principal. I know what series ratings of circuit breakers and fuses are and how it works, and I know that in the panelboard/load center world the manufacturers series rate their panels for use behind a specific main or up stream feeder breaker used as a to get a higher overall rating. But I also know that to attain that, they must test them in series with very specific components installed and it's a destructive testing process, so it is only done for high volume applications like residential / commercial panels where they sell thousands and thousands of them every year. I've never heard of this concept extending into primary type gear like LV Switchgear feeding LV MCCs.
I'm thinking that the Switchgear might be rated for 100kA even if you only need 65kA because that's getting to be a fairly common general spec now, but I don't think anyone has gone through the extreme expense of series rating an entire MCC lineup so that you can use a 65kA rated MCC in a system capable of 100kA by using the same manufacturer's switchgear in series. My bet is that the MCCs are rated for 65kA because the available fault current is <65kA at the MCC terminals, not because there is any "series rating" with the up stream gear.
But I've been out of the Switchgear business for a decade or more now, so is there something new out there that I'm not aware of?
