series rating and interupt capacity

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robert tucknott

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If series rated main service feeds same manufactor distibution panel (series rated)and 2 new panels are added to downstream of distibution of a different manufactor can AIC be choked down by current fuses on the 2 subfeeds 100 amp panels 120/208v 4 W 10K cb's transformer AIC at the load side 42K.
Referencing NEC 110.9. All is in new Building and new serive panels. Different contractors. It is represented the only way to make this code compliant is to replace the 2 news with the same manufactored panels service and dist. panel

Bob Tucknott
 
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kwired

kwired

Electron manager
Location
NE Nebraska
robert tucknott said:
If series rated main service feeds same manufactor distibution panel (series rated)and 2 new panels are added to downstream of distibution of a different manufactor can AIC be choked down by current fuses on the 2 subfeeds 100 amp panels 120/208v 4 W 10K cb's transformer AIC at the load side 42K.
Referencing NEC 110.9. All is in new Building and new serive panels. Different contractors. It is represented the only way to make this code compliant is to replace the 2 news with the same manufactored panels service and dist. panel

Bob Tucknott
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You mentioned 42K at the transformer. First, that suspiciously sounds like a shot at a standard AIC rating to CYA instead of an actual rating.

But regardless if that is actual rating or not, you need to factor in conductor sizes and lengths up to the point you are questioning. Resistance of those conductors will reduce what is available at the load end. If you happen to get below 10 kA by the time you get to the panels in question what series ratings are ahead of it really don't matter, you are below the 10k of the breakers you are using.

It doesn't take a lot of conductor length to reduce available fault current significantly. 15 to 20 feet of 200 amp or less conductor usually makes a pretty significant difference.
 
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dkidd

dkidd

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robert tucknott said:
If series rated main service feeds same manufactor distibution panel (series rated)and 2 new panels are added to downstream of distibution of a different manufactor can AIC be choked down by current fuses on the 2 subfeeds 100 amp panels 120/208v 4 W 10K cb's transformer AIC at the load side 42K.
Referencing NEC 110.9. All is in new Building and new serive panels. Different contractors. It is represented the only way to make this code compliant is to replace the 2 news with the same manufactored panels service and dist. panel

Bob Tucknott
Click to expand...

Only if the subpanels are listed by the manufacturer to have a series rating with the fuses.
 
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kwired

kwired

Electron manager
Location
NE Nebraska
dkidd said:
Only if the subpanels are listed by the manufacturer to have a series rating with the fuses.
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And they likely will be series rated with fuses, maybe not all fuses but typically RK1, RK5 or class J fuses is acceptable. What they are pretty much never rated with is series with other manufacturer's breakers. But as I said before, if available fault current drops enough by the time you get to said panel, none of those series ratings even matters anymore.

You also can't double series items, they aren't tested for that, meaning you can't have a branch breaker in series with a distribution breaker which is in series with a service breaker all depending on series ratings if otherwise applied at over their stand alone rating.
 
dkidd

dkidd

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here
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kwired said:
You also can't double series items, they aren't tested for that, meaning you can't have a branch breaker in series with a distribution breaker which is in series with a service breaker all depending on series ratings if otherwise applied at over their stand alone rating.
Click to expand...

I actually have seen a Siemens document that lists 4 breaker series ratings
 
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