Short circuit lowering Looped conductors

[Fordean]

Not really understanding this.
'
IN ORDER TO REDUCE SHORT CIRCUIT
CURRENT, E.C. SHALL ROUTE 30 FEET OF #12
AWG WIRE FOR EACH POWER AND LIGHTING
BRANCH CIRCUIT CONNECTED TO THE LCP.
RUN WIRE FROM PANEL, UP TO JOIST SPACE,
LOOP AND ROUTE BACK DOWN TO LCP.

Any input. Where would you loop this in. It's say 120volt circuit

 

[infinity]

I think that it has to do with the low SSCR ratings of the components of a lighting control panel.

 

[augie47]

See this done occasionally on controlled lighting systems with a 5k SCCR when the panel is close to the service panel and there is a high available current.
It was installed as noted, a "loop" of conduit between panels
(Likely it should be done more often than specified )
Hopefully the 30 ft requirement is based on an engineered design and not an arbitrary number.

 

[electrofelon]

Not really understanding this.
'. Where would you loop this in.

If it is cable like MC it's easy. If it's like and wire you will need a box.

 

[augie47]

Not really understanding this.
'
I

Any input. Where would you loop this in. It's say 120volt circuit

Assuming you are running circuits from a breaker panel to some sort of control panel such as lighting control, just route the conduit so you have 30ft of conductor.... to the ceiling and back down or along the wall and return.

 

[infinity]

As Augie stated you'll need a minimum of 30' of #12 conductor between the circuit breaker and the relay or control device on the lighting control panel. Make sure that you use #12 as larger conductors will change the 30' minimum calculated length requirement.

 

[don_resqcapt19]

A quick look at a fault current calculator shows that 30' of 12 AWG in EMT could reduce the fault current from 10kA to about 2kA

 

[infinity]

A quick look at a fault current calculator shows that 30' of 12 AWG in EMT could reduce the fault current from 10kA to about 2kA

I wonder why they would require 30' of wire if the calculation gets you down all the way down to 2kA. Many commercial panels have 22kA breakers so maybe they're accounting for higher than 10kA at the breaker?