How do you size an equipment grounding conductor for fire pump?

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elec_eng

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75hp 480V 3ph fire pump is directly connected to the secondary side of utility xfmr. Then the secondary conductors go from xfmr to the listed fire pump controller. Here is what I would size EGC for the fire pump but I am not so convinced.

1) From Xfmr to the listed fire pump controller
75 hp FLA=96A
96*1.25=120A #1 AWG
Per 250.30A(2) and 250.102(C), EGC is #6 AWG ??

Is it really Equipmnet bonding jumper? I am confused here as well because this is not a SDS, it is a service.

2) From the listed fire pump controller to the fire pump.
I am lost here. Per 250.122(D), EGC size is permitted to be based on the rating of the motor overload protective device. But 695.6(D) prohibits automatic protection against overloads. So, how you you size the EGC? Do I assume there will be overload protection and size EGC based on that? (Which would be #6 AWG). Or do I extend EGC from the xfmr to the controller to the fire pump as well?

Thank you for your answers in advance.
 
No, takers?

I have reviewed the code again, and I think 250.24(B) applies here. So I think I have to bring grouned conductor to the fire pump controller. It would be 4#1 from the xfmr to the fire pump controller?

250.122(D) still applies to EGC from the controller to the fire pump?

Can some one confrim if I am going with the right direction?
 
elec_eng said:
75hp 480V 3ph fire pump is directly connected to the secondary side of utility xfmr. Then the secondary conductors go from xfmr to the listed fire pump controller. Here is what I would size EGC for the fire pump but I am not so convinced.

1) From Xfmr to the listed fire pump controller
75 hp FLA=96A
96*1.25=120A #1 AWG
Per 250.30A(2) and 250.102(C), EGC is #6 AWG ??

Is it really Equipment bonding jumper? I am confused here as well because this is not a SDS, it is a service. .
Click to expand...
You do not need to install a EGC from the transformer. It would just be in parallel with the grounded neutral. However, I have heard of some utilities that do require it. Why, I do not know.
elec_eng said:
2) From the listed fire pump controller to the fire pump.
I am lost here. Per 250.122(D), EGC size is permitted to be based on the rating of the motor overload protective device. But 695.6(D) prohibits automatic protection against overloads. So, how you you size the EGC? Do I assume there will be overload protection and size EGC based on that? (Which would be #6 AWG). Or do I extend EGC from the xfmr to the controller to the fire pump as well?

Thank you for your answers in advance.
Click to expand...
The OC device is required to withstand the LRC of the motor plus the load of the other fire pump equipment. Using you information, it would be about 600 amps. Using table 250.122, the EGC would be #1 copper.

elec_eng said:
I have reviewed the code again, and I think 250.24(B) applies here. So I think I have to bring grounded conductor to the fire pump controller. It would be 4#1 from the xfmr to the fire pump controller?
250.122(D) still applies to EGC from the controller to the fire pump?.
Click to expand...
250.24 is listed a premise wiring.
 
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bob said:
The OC device is required to withstand the LRC of the motor plus the load of the other fire pump equipment. Using you information, it would be about 600 amps. Using table 250.122, the EGC would be #1 copper.
Click to expand...

Doesn't 250.122(D) allow to size EGC based on the rating of motor overload?

250.24 is listed a premise wiring
Click to expand...

250.24(A) is for a premise wiring but I don't think 250.24(B) is.
 
elec_eng said:
Doesn't 250.122(D) allow to size EGC based on the rating of motor overload?.
Click to expand...
695.6(D). The code goes out of the way to ensure that the pump is not disconnected from the power source for any reason short of total failure of the pump. The pump is to run until destruction.

elec_eng said:
250.24(A) is for a premise wiring but I don't think 250.24(B) is.
Click to expand...
You have a disconnect switch near the fire pump. 250.24(B) applies there.
I assume you have the service from the utility installed to the fire pump
disconnect and the service is considered outside the building per 695.6(A).
 
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bob said:
695.6(D). The code goes out of the way to ensure that the pump is not disconnected from the power source for any reason short of total failure of the pump. The pump is to run until destruction.
Click to expand...
Bob, I am aware of 695.6(D). Please look at my OP. I am just wondering whether I can apply 250.122(D) here or not. I guess your answer is no but I don't understand why. After all, you are sizing the EGC whether you have overload protection or not.

bob said:
You have a disconnect switch near the fire pump. 250.24(B) applies there.
I assume you have the service from the utility installed to the fire pump
disconnect and the service is considered outside the building per 695.6(A).
Click to expand...
I guess I mixed up my reference with 02 & 05 NEC. I meant to say 250.24(B) with 02 NEC and but it is 250.24(C) with 05 NEC. Did you mean to say 250.24(C) as well?

Yes, this will be installed as service entrance conductors.
 
elec_eng said:
Bob, I am aware of 695.6(D). Please look at my OP. I am just wondering whether I can apply 250.122(D) here or not. I guess your answer is no but I don't understand why. After all, you are sizing the EGC whether you have overload protection or not. .
Click to expand...
I do not see what that does for you. You still size the EGC from table
250.122. 695.6(D) states that the power conductors shall not have overload
protection.

elec_eng said:
I guess I mixed up my reference with 02 & 05 NEC. I meant to say 250.24(B) with 02 NEC and but it is 250.24(C) with 05 NEC. Did you mean to say 250.24(C) as well?
Click to expand...
The service is run from the transformer to the fire pump disconnect. The grounded conductor is bonded to the disconnect. I'm not sure what else is needed.
 
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