Upstream or down stream

[Fishn sparky]

Gents,
Dumb question. OCPD's, due they protect the upstream cabling or down stream cabling?

 

[MAC702]

Depends.

 

[ActionDave]

Mostly downstream. I the few times they "protect" upstream conductors there are specific size and length rules. 240.4 is the most common reference.

 

[retirede]

They can protect upstream conductors from downstream faults.

 

[don_resqcapt19]

They can protect upstream conductors from overloads, but not from short circuits and ground faults.

 

[retirede]

They can protect upstream conductors from overloads, but not from short circuits and ground faults.

It may be semantics, but I contend that the upstream conductors are protected from ground faults and short circuits IF those occur downstream.

 

[charlie b]

It may be semantics, but I contend that the upstream conductors are protected from ground faults and short circuits IF those occur downstream.

That is true, and it's not semantics. But I strongly suspect that Don intended his post to refer to faults upstream of the OCPD.

 

[charlie b]

Gents, Dumb question.

Not all forum members are male, and not all that are male are gentlemen. :happyno:

OCPD's, due they protect the upstream cabling or down stream cabling?

The basic rule appears in 240.4, which says that all conductors are required to be protected against overcurrent. 240.21 goes on to say that the protection must be at the point where the conductors receive their supply. There are other associated rules and exceptions. But these two are saying that, for the most part, the OCPD protects the downstream conductors.

 

[JFletcher]

"Line side" and "load side" are more correct terminology than "upstream" and "downstream", respectively. Breakers & fuses are installed to protect load side (downstream) wiring.

 

[retirede]

Not all forum members are male, and not all that are male are gentlemen. :happyno:

The basic rule appears in 240.4, which says that all conductors are required to be protected against overcurrent. 240.21 goes on to say that the protection must be at the point where the conductors receive their supply. There are other associated rules and exceptions. But these two are saying that, for the most part, the OCPD protects the downstream conductors.

No argument there. The upstream conductors are not considered protected per code.
But they are protected from downstream events in reality.

 

[ggunn]

Gents,
Dumb question. OCPD's, due they protect the upstream cabling or down stream cabling?

Think about it. If a fault occurs "upstream" (on the line side) of an OCPD, how much fault current passes through the OCPD? Answer: none.