Fire Pump Neutral Tapped Ahead of Electrical Service -

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cvirgil467

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Per 2008 NEC section 250-24(c) - the grounded conductor (neutral) shall terminate in the service disconnect switch. Understood.

I am confused when the fire pump service is tapped ahead of the building's main electrical service disconnecting service switch - does the neutral for the fire pump get bonded at the main service switchboard section (dedicated for the fire pump ) along with the building's main neutral conductor for the building's electrical service? Or do I install a separate grounding electrode at the fire pump controller (this is a combo setup with service disconnect and ATS) and install a main bonding jumper to the neutral terminal at the fire pump controller (bypassing any neutral connection with the building's electrical service)?

Not sure if that's clear.

Thanks.
c
 
We always bring the neutral to the FP disconnect switch and bond it to the enclosure. We also run a GEC to the GES. Load side of the disconnect needs only 3 conductors for a 3Ø pump.
 
See 230.82 (5), where it says "if provided with service equipment and installed in accordance with requirements for service-entrance conductors." The latter phrase in particular implies that you should bond stuff to the neutral and follow 250.24(C) like you would with any other service entrance.

(It is notable that the other sections within 230.82 don't have the same requirements.)
 
So would the fire pump neutral be connected to the GEC at the incoming service back at the main switchboard or does a separate GEC need to be installed at the fire pump controller and connected to the fire pump neutral?
 
If the existing GEC is terminated to the existing switchboard neutral, then you should provide a GEC tap to the fire pump disconnect neutral.

Alternatively, you can move the GEC connection to a point on the neutral ahead of where the fire pump is tapped to the other service conductors.

The NEC allows either way, but the method should be consistent among the different service disconnects.
 
jaggedben said:
Alternatively, you can move the GEC connection to a point on the neutral ahead of where the fire pump is tapped to the other service conductors.
Click to expand...

Would a GEC still be required within the separate fire pump disconnect since it's a service disconnect?
 
It is basically another service - run a GEC to it like you would any other service that were permitted to be installed.

The fact that they are not ordinarily allowed to be in the same vicinity as the other service disconnecting means makes them like a completely different service even if tapped to same supply conductors. GEC's of all allowed services in a building must tie together in some manner to minimize voltage differences between them.
 
The NEC allows the GEC to be landed at any point between the service point and the service disconnecting means. For example, in the meter socket. (Local rules or utility rules may be more restrictive, but the NEC is not.) If the GEC is landed ahead of the point where different sets of service entrance conductors are paralleled, then you do not need to bring GEC taps to each service disconnect. Otherwise, I believe you do.

Regardless, you need a main bonding jumper at each service disconnect. But that wasn't the question.
 
jaggedben said:
The NEC allows the GEC to be landed at any point between the service point and the service disconnecting means. For example, in the meter socket. (Local rules or utility rules may be more restrictive, but the NEC is not.) If the GEC is landed ahead of the point where different sets of service entrance conductors are paralleled, then you do not need to bring GEC taps to each service disconnect. Otherwise, I believe you do.
Click to expand...

The part I'm not getting is that if you have multiple service disconnects all fed from the same bus why should it matter if the GEC lands on the bus before them or in the middle of them or at the last one?
 
jaggedben said:
The NEC allows the GEC to be landed at any point between the service point and the service disconnecting means. For example, in the meter socket. (Local rules or utility rules may be more restrictive, but the NEC is not.) If the GEC is landed ahead of the point where different sets of service entrance conductors are paralleled, then you do not need to bring GEC taps to each service disconnect. Otherwise, I believe you do.

Regardless, you need a main bonding jumper at each service disconnect. But that wasn't the question.
Click to expand...
Ordinarily all the disconnecting means of a single service are supposed to be grouped in one location - fire pump service disconnect is supposed to be remote from other service disconnecting means. Can't say I know for certain the grounding rules for this situation, but since they are not grouped together I think that increases the risk of potential between the two. Especially if one has neutral load and the other doesn't.
 
kwired said:
Ordinarily all the disconnecting means of a single service are supposed to be grouped in one location - fire pump service disconnect is supposed to be remote from other service disconnecting means. Can't say I know for certain the grounding rules for this situation, but since they are not grouped together I think that increases the risk of potential between the two. Especially if one has neutral load and the other doesn't.
Click to expand...

I'm not quite sure what you're concern is, but regardless, the code allows three options for how to do it, and one of them, 250.64(D)(3), allows a single GEC to be brought to a common location on the supply side of the disconnects. See also 250.24(A)(1).
 
250.64(D)(1) Groudning Electrode taps with multiple disconnecting means- wondering if you could collect all of your grounding electrodes used (ground rod, ufer, water pipe, etc) to a common bus and just tap the ground bar where all of the grounding electrodes are collected. This way all of the services would be grounded to the same point.
 
See attached sketch for grounding/bonding of the fire pump controller. A few questions:

1. At the fire pump neutral tap back at the service - would this be considered bonded since it is tapping the man incoming neutral which terminates on the main neutral bus that is bonded?
2. At the fire pump controller the two equipment ground conductors are terminated on the fire pump ground lug. The lugs are physically connected to the fire pump controller enclosure, grounding the enclosure. Would the neutral conductor be considered bonded in two places since it connects to the fire pump enclosure?View attachment fire pump controller.pdf
 
cvirgil467 said:
See attached sketch for grounding/bonding of the fire pump controller. A few questions:

1. At the fire pump neutral tap back at the service - would this be considered bonded since it is tapping the man incoming neutral which terminates on the main neutral bus that is bonded?

No because you must have a main bonding jumper at each disconnect. There is no issue with the neutral bonded at both ends as these are service conductors and anything upstream of a disconnect can simply be bonded to the neutral.

2. At the fire pump controller the two equipment ground conductors are terminated on the fire pump ground lug. The lugs are physically connected to the fire pump controller enclosure, grounding the enclosure. Would the neutral conductor be considered bonded in two places since it connects to the fire pump enclosure?View attachment 20095
Click to expand...

The neutral from the main gear should be connected directly to the FP controller enclosure and there should be no EGC run with these conductors. The EGC from the FP motor and the genset should connect to the FP controller enclosure. And, of course, the genset should not have a bonding jumper. The GE you show at the genset connecting only to the EGC is fine but not required-it just serves as an optional GE.

And as far as the GEC goes, you could bring the all to a common busbar as you described. And jaggedben pointed out, it is not required to have GEC's run to each service disconnect-it can be any where downstream of the service point.
 
Thanks Texie.

What is missing from the sketch are the other 700 and 701 loads which have 4 pole ATSs fed off of the generator. The generator is a separately derived system. Mu concern is bonding the neutral at both points through the fire pump enclosure via the EGC from the generator.
 
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