MC cable when there is voltage drop

[Tainted]

In your GEMI screen shot under system parameters > Operating voltage you set 120 volts? I would think that should be your L-L voltage for voltage drop on a feeder?

It sets it to 120V as default, I can make it any number. But my suspicion is that it's supposed to be L-G because that's the worst case since L-G fault gives you a much higher voltage drop for the ECG

This is about the voltage drop and the fault clearing properties of the EGC...it uses the line to ground voltage and not the line to line voltage. However using 5x the OCPD rating for the ground fault current seems very low. I would expect for many systems using 3/0 the available line to ground fault current would far exceed 625 amps.

at 2x or 3x the breaker would still trip though. Code doesn't specifically say how fast the breaker is supposed to trip though... at 3x for example a Siemens 200A HQS breaker would trip between 15-90 seconds. Is this even good enough?

 

[tortuga]

It sets it to 120V as default, I can make it any number. But my suspicion is that it's supposed to be L-G because that's the worst case since L-G fault gives you a much higher voltage drop for the ECG

Good point

at 2x or 3x the breaker would still trip though. Code doesn't specifically say how fast the breaker is supposed to trip though... at 3x for example a Siemens 200A HQS breaker would trip between 15-90 seconds. Is this even good enough?

The closest thing is 110.10

@Tainted it says your a PE so I'd imagine your qualified to use the exception in 250.122 (B) and if your not on a 2020 or later code when it was added you could use 90.4 special permission, I imagine and AHJ would allow you to use a newer NEC if NY is on a older version.

 

[Tainted]

Good point

The closest thing is 110.10

@Tainted it says your a PE so I'd imagine your qualified to use the exception in 250.122 (B) and if your not on a 2020 or later code when it was added you could use 90.4 special permission, I imagine and AHJ would allow you to use a newer NEC if NY is on a older version.

Yes, I can do it. NYC will adopt the 2020 NEC with amendments pretty soon. Code is so vague but the vagueness will give me the advantage

 

[tortuga]

Yeah one option I have done is to use a GFPE breaker, then your not relying on the inverse time breaker for GF protection, A GFPE breaker is pretty expensive so you'd have to compare cost.

 

[letgomywago]

Yeah one option I have done is to use a GFPE breaker, then your not relying on the inverse time breaker for GF protection, A GFPE breaker is pretty expensive so you'd have to compare cost.

I'd say that if you're looking at custom mc as an option you're in the price range to look at this.

Idk if code wise this is acceptable but I'm sure any inspector would accept it.