Series rated system

[jkim780]

Questions on series rated system:

1) What would be the advantages & disadvantages of the series rated system over full rated system?

2) Can more than 2 OCPD be used for series combination?

3) When you have your main OCPD in remote location from your branch OCPD, how this series rated system works? I mean it is very likely you will have a different available fault current at two locations. How do your upstream OCPD of series combination play a role here? Do you have to take that into consideration? Like I asked in Q#2, can you use more than 2 OCPD for series combination?

4) When your main OCPD is located in remote location in a separate enclousre, do you also have to take your conductor impedance into consideration?

5) When would you use series rated system and when would not?

Thank you for your answers.

 

[ron]

Re: Series rated system

Q1) What would be the advantages & disadvantages of the series rated system over full rated system?
A1) Less Expensive

Q2) Can more than 2 OCPD be used for series combination?
A2) Manufacturers have series ratings for pairs of OCPD's.

Q3) When you have your main OCPD in remote location from your branch OCPD, how this series rated system works? I mean it is very likely you will have a different available fault current at two locations. How do your upstream OCPD of series combination play a role here? Do you have to take that into consideration? Like I asked in Q#2, can you use more than 2 OCPD for series combination?
A3) The stand alone rating (fully rated) of the main must be sufficient to withstand the available fault current at that location. The series rating must be high enough to withstand the available fault current at the "paired" device downstream.

Q4) When your main OCPD is located in remote location in a separate enclosure, do you also have to take your conductor impedance into consideration?
A4) conductor impedance is accounted for when calculating the available fault current at the downstream OCPD/equipment location to determine the required rating.

Q5) When would you use series rated system and when would not?
A5) I almost never use series ratings, except when I need an AIC rating that exceeds 65kAIC in a small molded case breaker, like a panelboard or switchboard, where a rating of a molded case breaker is not available higher than 65k.

[ March 23, 2005, 12:02 PM: Message edited by: ron ]

 

[ryan_618]

Re: Series rated system

One disadvantage of a series rated system is that selective coordination can't be achieved. This is more of a problem in the 2005 than in the 2002, although the 2002 does require the coordination in a few areas, like hospitals, power loss hazards and elevators.

 

[sandsnow]

Re: Series rated system

GE has triple ratings. A in series with B and A also in series with C
See publication DET-008A