Question EGC

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d0nut said:
It is possible to get a fairly low level fault, but that is probably an arcing fault and would most likely propagate into a lower resistance fault or self-extinguish, especially at lower voltages. Also, the cables don't instantly fail at their NEC listed ampacity. Refer to the TCC below for a sample of several different THHW conductor size damage curves plotted against a 60A thermal magnetic circuit breaker.

View attachment 2560215
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Ok i think i see.

What software you are using? Is it possible to plot the following i have inside fire pump controller and following EGCs load side of the fire pump controller and fire pump? Can you send me in private message if mods are not comfortable for view here??: 450A frame breaker, trip set at 2,118A with EGC size of 2/0 awg copper, 350 kcmil copper and 750 kcmil copper plotted?
 
I would be willing to bet there is no plans review person in the world that, given set of engineered drawings, worries about TCC, etc.
If I were dOnut I would be glad to provide that info IF you made your request on the back of a big check..........
 
augie47 said:
I would be willing to bet there is no plans review person in the world that, given set of engineered drawings, worries about TCC, etc.
If I were dOnut I would be glad to provide that info IF you made your request on the back of a big check..........
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I am plans reviewer. EGC sizing is not included in plans review? Sure Table 250.122 says it but i have coworker saying EGC should be sized based on main bonding jumper that EGC cannot be larger them MBJ as stated in previous threads but it can be in case of Fire pump.

So i am curious to see all this thats all
 
hhsting said:
I am plans reviewer. EGC sizing is not included in plans review? Sure Table 250.122 says it but i have coworker saying EGC should be sized based on main bonding jumper that EGC cannot be larger them MBJ as stated in previous threads but it can be in case of Fire pump.

So i am curious to see all this thats all
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The code never sets a maximum size for the EGC...it only sets a minimum size, and size greater than the minimum is code compliant.
 
don_resqcapt19 said:
The code never sets a maximum size for the EGC...it only sets a minimum size, and size greater than the minimum is code compliant.
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Yes i understand their is no such statement in NEC but being manager and chief of electrical he made that statement but with fire pump it does not work

Here is the deal that breaker inside the fire pump controller is served by 750kcmil copper utility conductors.

The internal breaker is 450A frame and its set at 2,118A trip.

So according coworker it cannot be larger than MBJ which is #2/0 awg copper. But the minimize according to Table 250.122 based on 2,118A trip is 350 kcmil copper.

So. I am just curious to see…doNut
 
I think the answer to your dilemma may lie in 250.122(D)(2).
Since it's a fire pump, the breaker is likely Instantaneous Trip, so from a Code standpoint (not engineering calculations) the 2,118 is irrelevant for sizing EGC. A dual element fuse rating would likely be around 700 amps for your 150HP motor, rewiring a #1 EGC which would need adjusting depending on the actual phase conductor size.
 
augie47 said:
I think the answer to your dilemma may lie in 250.122(D)(2).
Since it's a fire pump, the breaker is likely Instantaneous Trip, so from a Code standpoint (not engineering calculations) the 2,118 is irrelevant for sizing EGC. A dual element fuse rating would likely be around 700 amps for your 150HP motor, rewiring a #1 EGC which would need adjusting depending on the actual phase conductor size.
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Likely but no where in code or elsewhere other codes its stated type of breaker. Not sure what it is internally.

In case of not being sure then it would be 250.122(D)(1) general which points to rating of short circuit ground fault protection device which is set at 2,118A.
 
hhsting said:
Yes i understand their is no such statement in NEC but being manager and chief of electrical he made that statement but with fire pump it does not work

Here is the deal that breaker inside the fire pump controller is served by 750kcmil copper utility conductors.

The internal breaker is 450A frame and its set at 2,118A trip.

So according coworker it cannot be larger than MBJ which is #2/0 awg copper. But the minimize according to Table 250.122 based on 2,118A trip is 350 kcmil copper.

So. I am just curious to see…doNut
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No matter what type of breaker is used, I am going to apply (D)(2) for a fire pump. I really don't care if the breaker ever trips for that application.
 
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