Series Rated Combinations

[Grouch1980]

Hi all,
I have a few questions regarding series rated combinations:

1) Let's say, for example, the line side device is a fused switch, and it feeds a downstream panelboard with breakers. In order to achieve a series rated combination, must the line side fuse be current limiting? (on a side note, from what i read, i understand that one cannot use the UP-OVER-DOWN method on the line side device (from a current limiting curve) to determine if a combination is series rated due to the dynamic impedance of the downstream breakers... we would be in violation of NEC section 240.86(A) since the downstream breaker would not remain 'passive' during the operation of the line side device. The manufacturer would perform its own in-house testing).

2) In a series rated combination, where the downstream breakers have a lower AIC rating, can the panelboard itself also have a lower SCCR rating to match the breakers? I would assume yes since the upstream line side device is current limiting. and in the case of the panelboard, there would be no issue with dynamic impedance since we're only dealing with the bus bars of the panel.

Thanks in advance!

 

[templdl]

Current limiting or not and even comparing TC curves you can not assume a series rating. Anything that is series rated must be tested and listed as such. Check out he EATON Electrics catalog and it with SD how the fuses that are series rated with their panels. I believe the other major manufactures will have their table with series tasted devices also.
Remember that they must be tested.

 

[Grouch1980]

Current limiting or not and even comparing TC curves you can not assume a series rating. Anything that is series rated must be tested and listed as such. Check out he EATON Electrics catalog and it with SD how the fuses that are series rated with their panels. I believe the other major manufactures will have their table with series tasted devices also.
Remember that they must be tested.

I'm aware that they must be tested... I mentioned that at the end of my 1st question.

 

[jim dungar]

Series Combination ratings do not need to depend on the current limiting effect of up stream devices. In fact, it is entirely possible that a down stream device opens and clears before the upstream device responds at all.

Bus bars are not part of the series rating, so they need to be treated separately.

 

[GoldDigger]

The testing would have to be done by an NRTL to satisfy the NEC. When SquareD lists a series rating they do not do the testing themselves.
CE certification can be self issued.

 

[Grouch1980]

Series Combination ratings do not need to depend on the current limiting effect of up stream devices. In fact, it is entirely possible that a down stream device opens and clears before the upstream device responds at all.

Bus bars are not part of the series rating, so they need to be treated separately.

So the upstream device doesn't have to be current limiting?

 

[templdl]

So the upstream device doesn't have to be current limiting?

As I mentioned before refer to the manufactures catalog for OCPDs that are series rated. You would have to refer to the manufacturer's list of fuses that their breakers would be series rated with. You may feel free to take the time to review the catalog data yourself to see if CL fuses are necessarily used for series ratings which I would have assumed would be done.

 

[Grouch1980]

As I mentioned before refer to the manufactures catalog for OCPDs that are series rated. You would have to refer to the manufacturer's list of fuses that their breakers would be series rated with. You may feel free to take the time to review the catalog data yourself to see if CL fuses are necessarily used for series ratings which I would have assumed would be done.

Thanks everyone for the help! I had to dig a little further into some articles... what i was failing to understand was the mechanism at work in a series rated combination. check out pages 10-12 in this link... https://www.nema.org/Products/Documents/eng+series+rating+paper.pdf
it describes what is going on as the line and load side devices interact with each other during a short-circuit.. it's just the time-current curves of both devices that intersect so that both devices work together to interrupt the current. Current limiting devices on the line side may or may not be used. I went back to read everyone's comments, and things are making more sense now I imagine that as an added bonus of using CL devices, now the panelboard itself can be used at a lower SCCR rating.

 

[Maverick76]

Allowable series rating publications by manufacturer:

Square D: http://static.schneider-electric.us/docs/Electrical Distribution/Switchboards/2700DB9901.pdf

GE: http://apps.geindustrial.com/publib...TNR=Application and Technical|DET008A|generic

Eaton: https://eiabc.org/wp-content/uploads/2014/08/Series-Breaker-Applications.pdf

Siemens: https://www.downloads.siemens.com/d...aspx?pos=download&fct=getasset&id1=BTLV_41315

Cooper/Bussmann: http://www.cooperindustries.com/con..._Ele_Tech_Lib_Circuit_Breakers_Protection.pdf

 

[kwired]

Your products will typically have series ratings tested and published with some common fuse types upstream, but breakers upstream will always be ones made by same manufacturer, they will not always include every type though.

If you are far enough downstream that the available current is low enough to be below the downstream device rating - I don't believe you need to worry about series rating. Example you have 30kA available at main service/distribution equipment but if at the end of a feeder there is only 8kA available then 10kA breakers are acceptable whether series rated or not with what is upstream.

 

[flatlander]

Allowable series rating publications by manufacturer:

Square D: http://static.schneider-electric.us/docs/Electrical Distribution/Switchboards/2700DB9901.pdf

GE: http://apps.geindustrial.com/publib...TNR=Application and Technical|DET008A|generic

Eaton: https://eiabc.org/wp-content/uploads/2014/08/Series-Breaker-Applications.pdf

Siemens: https://www.downloads.siemens.com/d...aspx?pos=download&fct=getasset&id1=BTLV_41315

Cooper/Bussmann: http://www.cooperindustries.com/con..._Ele_Tech_Lib_Circuit_Breakers_Protection.pdf

thanks for the links