Interpretation of NEC 555.3 - Marina Ground Fault Protection

[buzzbar]

Hi all,

I know that this has been discussed many times, but I haven't found an answer that matches my exact situation.

Here's the deal: I'm working on a marina that is in the process of upgrading in phases. There are five (5) docks (salt water) that are fed from an existing 480V main distribution panel. Currently, there is a 3P150A breaker for each dock that feeds a transformer that is located on the floating docks.

Phase 1 is replacing docks 4 and 5. The feeder for dock #4 will be increased from 150A to 225A, so we will be altering (replacing) the existing feeder. Since both docks will be replaced with new wiring, it needs to be brought up to the latest code, which in Article 555.3, it says:

555.3 Ground-Fault Protection. The main overcurrentprotective device that feeds the marina shall have groundfault protection not exceeding 100 mA. Ground-fault protection of each individual branch or feeder circuit shall bepermitted as a suitable alternative.




Each new dock will again, have a transformer on the floating dock that will step down from 480V to 120/208V (don't get side-tracked by the 208V, I'm aware of the FPN about that).

My local AHJ says that the main 480V feeder coming from shore to the transformer needs to have ground fault protection (GFP). I would argue that 555.3 allows for the GFP to be located on the main breaker of the secondary panel (or at each sub-feeder for pedestals) since 555.3 says, "Ground-fault protection of each individual branch OR feeder circuit shall be permitted as a suitable ALTERNATIVE".

Talking to my Eaton rep, he says that they don't normally GFP the primary side of the transformers, but they can certainly build them that way.
At the very least, it's a very vague couple of sentences, and should be cleared up.

Thoughts?

Thanks!

Andy

 

[david]

I have never wired a dock nor have I ever inspected wiring involving a dock.

It sounds like the supply to the dock is a 480 volt feeder.
The section you quoted states the supply to the dock needs GFP.

 

[charlie b]

I think that once you park your truck in the nearby lot, you are in the "marina." A single floating dock does not a marina make. The "marina" comprises all five floating docks and a chunk of land from which you walk onto each dock. The article you cited is talking about the main circuit breaker on the main distribution panel that is upstream of all the floating docks. It might even be upstream of what you described as the "480V main distribution panel." At what point does a power source first cross the property line, and where does that set of conductors terminate? That is the point at which the GFP is required. You don't also need to provide GFP on each feeder to each floating dock.

 

[buzzbar]

Yes, but the second sentence says that "Ground-fault protection of each individual branch OR feeder circuit shall be permitted as a suitable ALTERNATIVE"

"Alternative" means that you can do one or the other, correct? I agree, it's a vague article, which is why I'm bringing this up.

 

[charlie b]

Not having access to a one-line diagram, I will assume that from the outside world there is one utility line that terminates on the "480V main distribution board" that you mentioned. I will further assume that this same board supplies power to a building (marina office, perhaps), to site lighting, and to the five floating docks. So from this board you have five feeders, each serving one floating dock. You are allowed, but not required, to meet the requirement by putting GFP protection on each of the 5 feeders. You would also have to put GFP on the feeder that serves the building, and the feeder that serves the small panel that distributes power to the site lights. OR, if you prefer, you can put one GFP device on the main breaker to the board, and call it a day.

By the way, which marina are you working on? I did a project some years ago at the Des Moines Marina, which would not be too far from your location.

 

[luckylerado]

I believe the Transformer would be considered a service in this case on the floating structure and is in violation. 555.4
The 100mA protection for the feeder needs to be on the shore. This does not get you out of the 5mA level of protection on the 15 or 20 amp receptacles which should be accomplished at the breaker for best practice protection in my mind. 555.19B1

Need to keep straight the difference between feeders and branch circuits as it becomes very important for this application.

This is from the 14 handbook and refers to 553.4 and applies to 555.3

553.4 Location of Service EquipmentThe service equipment for a floating building sh all be located
adjacent t o, but not in or on, the building or any floating structure.
The main overcurrent protective device that feeds the floating
structure shall have ground fault protection not exceeding
100 mA. Ground fault protection of each individual branch or
feeder circuit shall be permitted as a suitable alternative.

"This requirement ensures that supply conductors to a floating
building can be disconnected in an emergency, such as during a
storm, when the floating building has to be moved quickly. Service
equipment is not permitted to be installed on the floating
building and any other floating structure such as a wharf or pier.
Overcurrent protection for supply conductors is provided by
the service equipment, and since these conductors may develop
leakage, ground fault protection is required at this main device or,
alternatively, for each feeder or branch circuit. Factors such as
corrosion or lack of maintenance may cause ground faults to the
metal surfaces of floating buildings or shore-powered vessels.
Persons in contact with these metal surfaces, in proximity to the
water surrounding the metal surface, or attempting to exit the
water via a metal swim platform or ladder may be subjected to an
electrical shock. While branch-circuit GFCI devices, which may trip
as low as 4 mA, are permitted to be used, this is not practical for
all floating buildings. Therefore, the ground-fault current level of
the device is not permitted to exceed 100 mA. Devices operating
at current levels higher than those specified for a Class A GFCI in
UL 943, Standard for Ground-Fault Circuit Interrupters, do not provide
GFCI protection of personnel. See Article 100 for the definition
of ground-fault circuit interrupter."

 

[luckylerado]

Marina Guard

Check out this product to meet the 100mA level of protection.

http://www.bender.org/documents/MarinaGuard_manual_NAE1095810.pdf

Might also consider reading up on the safety aspect of an isolation transformer at the shore when there are areas for swimmers near marinas.

I did not ask. Is there fuel distribution?

 

[charlie b]

I believe the Transformer would be considered a service in this case on the floating structure and is in violation. 555.4

In my copy of the 2014 NEC, the article you would be citing is 555.7. But this is not a "service." That word means that the serving utility is on the other side of the wire. The transformer on the floating dock is fed from a panel that is owned by the owner of the marina, not by the utility. The utility is somewhere upstream of the main service panel named in the original post.

Also, there are no floating buildings under discussion here. These are floating docks, and serve as the parking places for boats.

 

[buzzbar]

Not having access to a one-line diagram, I will assume that from the outside world there is one utility line that terminates on the "480V main distribution board" that you mentioned. I will further assume that this same board supplies power to a building (marina office, perhaps), to site lighting, and to the five floating docks. So from this board you have five feeders, each serving one floating dock. You are allowed, but not required, to meet the requirement by putting GFP protection on each of the 5 feeders. You would also have to put GFP on the feeder that serves the building, and the feeder that serves the small panel that distributes power to the site lights. OR, if you prefer, you can put one GFP device on the main breaker to the board, and call it a day.

By the way, which marina are you working on? I did a project some years ago at the Des Moines Marina, which would not be too far from your location.

The 480V panel is strictly for the five (5) docks. It is located right next to a PSE pad-mount transformer. So no buildings or site lighting to deal with. I have provided pricing to put one GFP on a new MDP, which would cover EVERYTHING. But I was thinking that the GFP on the main breaker of the transformer's secondary panel would meet the 'alternative' criteria. Isn't this a viable 'alternative'?

Also, if we DO install the GFP at the main MDP, would we still need to put the GFP on the secondary side of the transformers? Being a separately derived system, I'm thinking we do.

The marina is in La Conner, up North. We just did some work at Des Moines Marina as well, small world!

Thanks!

Andy

 

[buzzbar]

In my copy of the 2014 NEC, the article you would be citing is 555.7. But this is not a "service." That word means that the serving utility is on the other side of the wire. The transformer on the floating dock is fed from a panel that is owned by the owner of the marina, not by the utility. The utility is somewhere upstream of the main service panel named in the original post.

Also, there are no floating buildings under discussion here. These are floating docks, and serve as the parking places for boats.

Agreed, this is not a service. Besides, we are using an Eaton 'substation', which is designed to be installed on a floating dock. They have a transformer and a secondary panel all built into one unit. They're very slick (but very expensive!). See attached picture.

 

[buzzbar]

Marina Guard

Check out this product to meet the 100mA level of protection.

http://www.bender.org/documents/MarinaGuard_manual_NAE1095810.pdf

Might also consider reading up on the safety aspect of an isolation transformer at the shore when there are areas for swimmers near marinas.

I did not ask. Is there fuel distribution?

In fact, those devices are pre-installed. I'm just trying to get opinions as to where they would be required. Oh, and no fuel at this marina.

 

[buzzbar]

I think that once you park your truck in the nearby lot, you are in the "marina." A single floating dock does not a marina make. The "marina" comprises all five floating docks and a chunk of land from which you walk onto each dock. The article you cited is talking about the main circuit breaker on the main distribution panel that is upstream of all the floating docks. It might even be upstream of what you described as the "480V main distribution panel." At what point does a power source first cross the property line, and where does that set of conductors terminate? That is the point at which the GFP is required. You don't also need to provide GFP on each feeder to each floating dock.

Read the second sentence in 555.3. When is the suitable ALTERNATIVE allowed? I just can't get past the fact that ALTERNATIVE means one or the other. Wouldn't a GFP on the secondary side be the "other"? Or am I just over-analyzing this?

 

[charlie b]

Start at the service, for that is where the code requires the GFP to be located. The service is located at your 480V main distribution panel. You can satisfy the requirement by putting a GFP on the main breaker of that panel. You can instead, as an alternative, put a GFP device on each of the five feeder breakers on the same panel. On the other side of the tranformers that are on the floating docks, you are no longer dealing with the main service to the marina. Therefore, as I see it, putting anything on the secondary of those transformers will not satisfy the requirement. But why do that anyway, when one single GFP device is all you need?

 

[buzzbar]

Start at the service, for that is where the code requires the GFP to be located. The service is located at your 480V main distribution panel. You can satisfy the requirement by putting a GFP on the main breaker of that panel. You can instead, as an alternative, put a GFP device on each of the five feeder breakers on the same panel. On the other side of the tranformers that are on the floating docks, you are no longer dealing with the main service to the marina. Therefore, as I see it, putting anything on the secondary of those transformers will not satisfy the requirement. But why do that anyway, when one single GFP device is all you need?

Okay, that makes sense. Thanks for taking the time to explain this. Last question: If the GFP is located on the 480V side, would the GFP still be required on the secondary side at the dock transformer?

 

[luckylerado]

In my copy of the 2014 NEC, the article you would be citing is 555.7. But this is not a "service." That word means that the serving utility is on the other side of the wire. The transformer on the floating dock is fed from a panel that is owned by the owner of the marina, not by the utility. The utility is somewhere upstream of the main service panel named in the original post.

Also, there are no floating buildings under discussion here. These are floating docks, and serve as the parking places for boats.

I must concede. These are feeders and not a service.

I point at 553 only because 555.3 in the 14 handbook points to 553.4 for the explanation of the requirement.

 

[luckylerado]

Start at the service, for that is where the code requires the GFP to be located. The service is located at your 480V main distribution panel. You can satisfy the requirement by putting a GFP on the main breaker of that panel. You can instead, as an alternative, put a GFP device on each of the five feeder breakers on the same panel. On the other side of the tranformers that are on the floating docks, you are no longer dealing with the main service to the marina. Therefore, as I see it, putting anything on the secondary of those transformers will not satisfy the requirement. But why do that anyway, when one single GFP device is all you need?

I disagree. It is my understanding that primary side GFP only protects from faults on the primary side of the transformer. I do not see how one is protected from ground faults on the secondary side unless it is sufficient to trip the OCP device on the branch circuit.

Are you pulling a GEC from the dock steel for this transformer?

I believe that in this case. With the transformer on the dock, the primary feeder must be GF protected and so must the secondary "feeder" would also require additional protection or alternately, each branch circuit supplied by that secondary feeder.

 

[buzzbar]

I disagree. It is my understanding that primary side GFP only protects from faults on the primary side of the transformer. I do not see how one is protected from ground faults on the secondary side unless it is sufficient to trip the OCP device on the branch circuit.

Are you pulling a GEC from the dock steel for this transformer?

I believe that in this case. With the transformer on the dock, the primary feeder must be GF protected and so must the secondary "feeder" would also require additional protection or alternately, each branch circuit supplied by that secondary feeder.

Yes, there will be a GEC for brought back to shore for the 480V primary feeder.

Your comment on the GFP for the secondary side makes sense to me since it's a separately derived system. It's pretty much 'SOP' to put GFP on the secondary side. I was just thinking that we don't need it on the primary side, but Charlie 'shed some light' on that subject.

Thanks!

 

[charlie b]

I disagree.

And you are certainly welcome to do so.

It is my understanding that primary side GFP only protects from faults on the primary side of the transformer.

The transformer is not a player in this discussion. The rule cited in post #1 is all about the main service to the marina. The fact that there is a transformer on the dock has nothing to do with GFP protection at the main service.

I do not see how one is protected from ground faults on the secondary side unless it is sufficient to trip the OCP device on the branch circuit.

There are ways to provide protection on the secondary side of the transformer, and I agree it would be a good idea to do so. But that is not related to the rule under discussion.