Double Fused Service

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WCS68iou1

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Mike;

Is is NEC legal to have a double fused or double Current limit, ie:C.B. of the same size on a 3 phase 4 wire 480v/277 cold sequence electrical service?

There is a existing 800 Amps I-Line Panel Board. We were thinking to install an additional 800 Amps Circuit Breaker in the same I-Line Panel Board and use it as a Sub-Breaker, to feed cold sequence into a new 800 Amp CT cabnet for metering. There will be no use for any other breakers in the panel, and will only be used this way, locked out by the utility company.

Is this legal to have the same size? Or does load breaker have to be larger or smaller ?

Thank You
William Steenstra
Modern Electric Co.
 

charlie b

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Location
Seattle, WA
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Electrical Engineer
I do not know what is meant by "cold sequence." But if you are asking if two sets of fuses, or two breakers, can be in series with each other, with both having the same rating, there is no code rule against doing that.

Welcome to the forum.
 

tkb

Senior Member
Location
MA
Cold Sequence is a term used by the POCO around here.

Cold Sequence = Main before the metering
Hot Sequence = Main after the metering

Most all houses are Hot Sequence.
 

don_resqcapt19

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Location
Illinois
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retired electrician
Tim,
The disconnect on the line side of the metering equipment can be the main or service disconnect, but it also can be just a disconnect and not trigger the other rules that are involved when it is the service disconnect. 230.82(3) permits the meter disconnect to be on the supply side of the service disconnect.
 
Mike;

Is is NEC legal to have a double fused or double Current limit, ie:C.B. of the same size on a 3 phase 4 wire 480v/277 cold sequence electrical service?

There is a existing 800 Amps I-Line Panel Board. We were thinking to install an additional 800 Amps Circuit Breaker in the same I-Line Panel Board and use it as a Sub-Breaker, to feed cold sequence into a new 800 Amp CT cabnet for metering. There will be no use for any other breakers in the panel, and will only be used this way, locked out by the utility company.

Is this legal to have the same size? Or does load breaker have to be larger or smaller ?

Thank You
William Steenstra
Modern Electric Co.

It violates the coordinated protection when they operate in series, although if there are no other branches it is immaterial. OSHA requires coordinated protection for installations falling under 1910 Subpart S. The NEC has much narrower requirements for the same.

With breakers, you can have zone coordinations where you can trip the upstream breaker always. That woudl satisfy the coordinated protection requirements.

Again, from the practical standpoint of view I would not worry, but you asked for legal compliance.
 
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