Series Rated???
Series Rated???
(OP)
I am feeding a new panel in a building from an adjacent building through an underground sleeve we installed between the two buildings. The panelboard manufacturer is telling me I want the feeder to be series rated.
What does this mean?
Thanks.
What does this mean?
Thanks.






RE: Series Rated???
RE: Series Rated???
RE: Series Rated???
Series rating inherently require both the upstream and downstream devices to trip to interrupt the fault. This is often pointed out in a manner that suggests that using a fully rated combination would not have both devices tripping. That is not a true conclusion; it is often impossible to distinguish a series rated combination from a fully rated combination if only looking at the trip characteristics of the two devices.
RE: Series Rated???
A fully-rated system allows coordinated settings so that this can be avoided.
RE: Series Rated???
RE: Series Rated???
Some systems/circuits are quite suited to series-rated, since the components are cheaper and maybe the loads aren't that critical. Some aren't.
If your manufacturer is doing this to save YOU money, then you only have to decide how important the loads are. If he's doing it to save HIMSELF money (like he already gave you a price, but didn't indicate that series-rated equipment was to be used) that's another story.
RE: Series Rated???
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: Series Rated???
I am afraid that it will be an adder to go with series rated equipment, but you're telling me otherwise, correct, so I should ask him for a credit, correct?
RE: Series Rated???
Fully-rated gives you the possibility of isolating a fault on, say a 20A C/B supplying a lighting circuit, to that 20A C/B instead of knowing that the main device must trip for a major fault on that 20A circuit if the system were series-rated.
Or, this may be an example of where a design engineer should be retained.
RE: Series Rated???
I suspect he is trying to save a few bucks and in turn get his equipment installed. I'm not interested in saving a few bucks to go this route, primarily because I really don't care to go with his equipment.
My biggest concern is that there's some inherent risk in not going series rated....but you all are telling me otherwise.
RE: Series Rated???
I am all in favor of selective coordination where it can be readily achieved, and all selectively coordinated combinations will be fully rated, but the vast majority of all fully rated combinations ARE NOT selectively coordinated.
If you truly need selective coordination at lower load currents, say less than 400A, and have reasonable fault currents, say above 5kA, fuses are about the only way to get there. But then you have fuses to deal with rather than circuit breakers, and fuses are not the answer to all electrical protection issues as a certain fuse manufacturer would have you believe.
If you did not specify either fully rated or series rated, the manufacturer is free to supply which ever as either will meet the interrupting duty requirements.
RE: Series Rated???
RE: Series Rated???
If the impedance check even gets you close, route the feeder so as to use enough cable length so that the cable impedance is enough to limit the available fault current to an acceptable value.
respectfully
RE: Series Rated???
But if at some point in the future, someone replaces that upstream breaker with another brand, there goes your series rating. Fully-rated systems probably reduce your liability and risk to some degree.
RE: Series Rated???
RE: Series Rated???
Don