# fire pump bonding



## sunkduck (Jun 16, 2015)

This generator also feeds emergency systems through the building. Therefore, the ground wire pulled from the generator is bonded to the main service neutral and grounding electrodes.


----------



## RIVETER (Sep 26, 2009)

sunkduck said:


> I have a fire pump and it is fed from a utility transformer and also fed from an emergency back up generator. This generator does not have a switched neutral. I pulled a neutral out to the transformer and I pulled a ground wire out to the generator. These wires both land on the same lug. Should I treat this fire pump as a separately derived system in the form of grounding and bonding? (grounding electrodes like water pipe, steel, concrete encased electrodes, etc.)


Keep in mind that GROUNDING and BONDING are different animals. Grounding has to do with lightning. You can ground any electrical equipment whether it is a separately derived system, or not.


----------



## micromind (Aug 11, 2007)

Does the gen serve line to neutral loads?


----------



## telsa (May 22, 2015)

It's the GEN-SET that's the SDS...

And as described, yours fits the definition, textbook perfect. So it's going to need all of the SDS bonding described in the NEC Handbook/ Codebook.

There's no doubt about that.

&&&

I've never seen a fire pump controller that didn't have its own control transformer... I've never pulled fire pump feeders in anything other than three hots. The usual office error is wildly undersizing the grounding conductor -- basing it off of the others, the hots, instead of the size of the OCPD -- ie the circuit breaker. 

The correct size of grounding conductor will usually be found to just barely slip inside the lug provided inside the fire pump controller. Those boys don't provide an oversized lug, not at all.

In EM mode the gen-set described figures to feed lighting fixtures and whatnot... 

You'd better assume that all of those loads are L-N.


----------



## sunkduck (Jun 16, 2015)

The gen does serve line to neutral loads on its other ats... 

And the neutral/wire pulled out to the transformer is not to be used as a grounded conductor more so just main bonding conductor sized accordingly.. the controllers does have its own control transformer


----------



## cabletie (Feb 12, 2011)

Why would the neutral wire pulled to the transformer not be a grounded conductor. The two terms are the same


----------



## cabletie (Feb 12, 2011)

Regardless if the neutral/ grounded conductor is used at the controller, it would still need to be run to the controller. The neutral/grounded conductor is required to be run to the first system disconnect. 

I guess it is possible that the controller is not the service disconnect. In which case you would not have to run the neutral/grounded conductor from the disconnect to the controller.


----------



## sunkduck (Jun 16, 2015)

And see that is the deal the controller is the first means of disconnect from the transformer..the first means of disconnect from the generator is in the generator...And the ground wire that runs from the generator is tied into the mdp/buildings grounding electrodes already..so the question is is since I have a wire that connects everything together from the generator why would I need to do it again and give the ground a choice of the path of least resistance


----------



## cabletie (Feb 12, 2011)

Does the transfer switch for the building load switch the neutral when it transfers?

Does the fire pump transfer switch switch the neutral when it transfers?

Basically are they three pole or four pole transfer switches. 

If they switch the neutral, the grounding electrode system is lost when it transfers. If that happens then you need a grounding electrode system at the generator (first system disconnect). The generator disconnect/over current protection then acts as the service disconnect. 

In this case you would have two service disconnects, not grouped together, and you would need signage to indicate the location of the two disconnects at each service disconnect locations.


----------



## telsa (May 22, 2015)

Based on the OP I'm seeing...

Poco transformer to a dedicated Service -- just for this fire pump room -- with its secondaries sized to that Service -- connected as a wye distribution -- no grounding conductor between the Poco pad mounted transformer and the dedicated Service -- sitting on its own pad -- fed as a service lateral.

At this dedicated fire pump Service, the NEMA3R box is grounded to a Ufer laid below the pad -- probably running off under the fire pump room, itself.

From the dedicated fire pump Service 3 hots (480V ?) run off to the fire pump controller -- together with a grounding (green) conductor sized for the OCPD -- ie a huge grounding conductor virtually the same size as any of the hots. If your office got this size right, it figures to be a career first event. The only fellows that size it right play with life-critical circuits all the time. It's a totally different mind set -- and NEC area.

I'm assuming that an integral ATS is built into the fire pump controller that will ONLY switch over to fire up the gen-set in the event of Poco power failure. Otherwise, the fire pump will run until manually stopped or it melts down.

Should the Poco drop out, the fire pump controller ATS would kick in and fire up the gen-set PDQ... and carry on the good work.

I'm then assuming that the gen-set is so sized that it's permitted to power OTHER EM circuits in the protected structure, a bunch of EM lights, mostly, L-N loads. This demands EE intervention. You want him pulling the liability for the design scheme and sizing.

The question then becomes exactly where to bond these neutral loads...

For such a highly engineered design, truth to tell, I'd simply throw the matter back to the EE that designed the system, again. The reason: politics. EEs love to make these calls, and are paid to. You are expected to perform design services for free, you're an electrician.

And from the Internet, I can't see your installation, the gear, any of the complications that are possible, any of the cut sheets for the gear... etc.


----------



## sunkduck (Jun 16, 2015)

It is a three pole transfer switch...so everything stays bonded


----------

