RK5 series rating

Status
Not open for further replies.
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
Someone double check me here. I find it hard to believe I can't get a series rating from a 200A RK5 fuse with 65k down to a standard 10k branch breaker. I didn't check other brands, but this is Siemens and I'm not seeing it in their charts. I can go to a class T fuse and get it.
 
electrofelon said:
Someone double check me here. I find it hard to believe I can't get a series rating from a 200A RK5 fuse with 65k down to a standard 10k branch breaker. I didn't check other brands, but this is Siemens and I'm not seeing it in their charts. I can go to a class T fuse and get it.
Click to expand...

With tested/published combinations it’s entirely possible.
 
ron said:
If you look at page 33 of the link below, you can get 100kA from a "BL" CB (10kA fully rated) and a "T" fuse.

Download center

www.siemens.com www.siemens.com
Click to expand...
xptpcrewx said:
With tested/published combinations it’s entirely possible.
Click to expand...
Yeah I saw the rating using class T. I just would have thought an RK5 would rate with a 10k MCCB no problem, I was surprised. 65k 200A frame breakers typically rate with a 10k.
 
electrofelon said:
Someone double check me here. I find it hard to believe I can't get a series rating from a 200A RK5 fuse with 65k down to a standard 10k branch breaker. I didn't check other brands, but this is Siemens and I'm not seeing it in their charts. I can go to a class T fuse and get it.
Click to expand...
This is an example of how not all current limiting fuses are created equal, showing that simply installing 'current limiting' fuses is not the answer to high SCCR vs low AIC problems.
 
jim dungar said:
This is an example of how not all current limiting fuses are created equal, showing that simply installing 'current limiting' fuses is not the answer to high SCCR vs low AIC problems.
Click to expand...
Yes, that is why I was surprised there wasn't a series rating, being that it was a current limiting fuse. A class T is a fast acting fuse, can we glean the existence of a series rating because of that characteristic?
 
petersonra said:
I would just get a 65 k rated breaker. Probably costs less than adding in a set of fuses and fuse block.
Click to expand...
Yes A circuit breaker and enclosure would have been an option and would definitely have the series rating with standard branches. However the fused switch has already been purchased and mounted. Another option would be to use the rk5's, and use a MB panel board with a fully rated main (22k) which would rate with the branches. probably not a huge difference in cost for either of these options I would guess not more than 2 to 300 bucks.
 
I see a lot of devices that are Series Listed with Class RK1 fuses, they are exactly the same physical size as RK5 but offer better current limitation. The problem with that is that issue of an RK5 fitting in the same holder; someone can replace an RK1 with an RK5 and the series listing is no longer valid. that's why many are going to Class T or Class J fuses. The problem there is the disconnect mfrs and distributors only stocking the RK1/5 versions.
 
electrofelon said:
Yes, that is why I was surprised there wasn't a series rating, being that it was a current limiting fuse. A class T is a fast acting fuse, can we glean the existence of a series rating because of that characteristic?
Click to expand...
Yes. But this fast acting cause coordination issues preventing some transformers and motors from being energized.
 
Jraef said:
I see a lot of devices that are Series Listed with Class RK1 fuses, they are exactly the same physical size as RK5 but offer better current limitation. The problem with that is that issue of an RK5 fitting in the same holder; someone can replace an RK1 with an RK5 and the series listing is no longer valid. that's why many are going to Class T or Class J fuses. The problem there is the disconnect mfrs and distributors only stocking the RK1/5 versions.
Click to expand...
IIRC, I don't remember seeing any differentiation in the Siemens series rating chart between different class R fuses. The only field is "R"
 
electrofelon said:
IIRC, I don't remember seeing any differentiation in the Siemens series rating chart between different class R fuses. The only field is "R"
Click to expand...
Class R fuses are interchangeable. There is no way to prevent an RK5 versus RK1 substitution.
 
Status
Not open for further replies.
Top