Junction boxes under dock

[Bjenks]

I believe I have found the problem to a customer?s electrical issue. They ran power out to the 3 fingers of a marina underneath the dock and had some pull boxes installed 20 years ago. It looks like they are NEMA 3R and I believe water has gotten in and started to corrode the spices.

This is a fixed pier and the junction boxes are for feeders and obviously below the electrical datum line. Looking at NEC 2008 555.9 says to use from what I can tell NEMA 6P enclosures only. However, it seems to say you can use junction boxes for floating piers only. Does anyone else get this or am I miss-reading it? I think NEMA 6P is the only acceptable box to meet the code, would you agree?

 

[mcclary's electrical]

I believe I have found the problem to a customer?s electrical issue. They ran power out to the 3 fingers of a marina underneath the dock and had some pull boxes installed 20 years ago. It looks like they are NEMA 3R and I believe water has gotten in and started to corrode the spices.

This is a fixed pier and the junction boxes are for feeders and obviously below the electrical datum line. Looking at NEC 2008 555.9 says to use from what I can tell NEMA 6P enclosures only. However, it seems to say you can use junction boxes for floating piers only. Does anyone else get this or am I miss-reading it? I think NEMA 6P is the only acceptable box to meet the code, would you agree?

I don't have an 08' since we're still on 05'. But 555.9 (05') covers fixed and stationary piers.

 

[ivsenroute]

If you are in the NEC 08 then yes, a NEMA 6P would suffice but all of the splices in the box would have to be sealed and listed for submersion. Otherwise, you will be mounting 12" above the dock surface.

 

[buzzbar]

On fixed piers, all splices have to be above the datum plane. The 'submersion' rated enclosures are for floating docks only. This is an update to the '08 code.

 

[hardworkingstiff]

On fixed piers, all splices have to be above the datum plane. The 'submersion' rated enclosures are for floating docks only. This is an update to the '08 code.

I would like to add the way I read it, a junction box on a fixed pier would have to be at least 12 in. above the deck as well as above the datum plane.

I always understood the "rated for submersion" part of this section to apply to the splices, not the box.

 

[iMuse97]

I would like to add the way I read it, a junction box on a fixed pier would have to be at least 12 in. above the deck as well as above the datum plane.

I always understood the "rated for submersion" part of this section to apply to the splices, not the box.

Quote: 555.9 "Conductor splices, within approved junction boxes, utilizing sealed wire connector systems listed and identified for submersion shall be permitted.... for floating piers." NEC 08

But yes, fixed piers above the deck.
And on a fixed structure, why wouldn't you want to keep things up where they are easily accessible?

 

[hardworkingstiff]

Quote: 555.9 "Conductor splices, within approved junction boxes, utilizing sealed wire connector systems listed and identified for submersion shall be permitted.... for floating piers." NEC 08

Karl,
Is this posted to say you think "submersion" applies to the junction box and not the conductor splices?

 

[hurk27]

Quote: 555.9 "Conductor splices, within approved junction boxes, utilizing sealed wire connector systems listed and identified for submersion shall be permitted.... for floating piers." NEC 08

But yes, fixed piers above the deck.
And on a fixed structure, why wouldn't you want to keep things up where they are easily accessible?

That was my first thought in reading your first post.

When I did my Dads marina back in "1990", Any J boxes was 2' above the floating deck, and loaded with a potting compound, but that was salt water, but Lake Michigan water isn't much better

 

[ivsenroute]

I would like to add the way I read it, a junction box on a fixed pier would have to be at least 12 in. above the deck as well as above the datum plane.

I always understood the "rated for submersion" part of this section to apply to the splices, not the box.

I can't agree with that interpretation. A floating pier can have splices below the dock, above the water and below the datum field if the splices are listed for submersion and inside a box rated for that application.

Fixed pier connections must always be a minumum of 12" the deck but not below the datum field.

 

[hardworkingstiff]

And on a fixed structure, why wouldn't you want to keep things up where they are easily accessible?

If you are pulling 350kcmil conductors, it's probably a lot easier to install the junction box in the dock with a removable deck cover than above the deck, especially if the deck is 3 or 4 feet above the datum plane. (It's a reason why, but still won't meet code).

 

[hardworkingstiff]

I can't agree with that interpretation. A floating pier can have splices below the dock, above the water and below the datum field if the splices are listed for submersion and inside a box rated for that application.

Is a NEMA 3R box sufficient in your interpretation?

Fixed pier connections must always be a minumum of 12" the deck but not below the datum field.

I agree that's what the code says, but fixed pier decks are often feet above the datum plane.

 

[hardworkingstiff]

08 handbook

08 handbook

From the handbook (after section 555.9).

This section was revised for the 2008 Code to allow the use of sealed, waterproof wire-to-wire splices in approved junction boxes that are below the datum plane but above the waterline where the connector systems are listed and indentified for submersion.

This seems to specifically call for the splices to be rated for submersion. I don't believe it specifically calls for the junction boxes to be rated for submersion, just to be approved for the location which will always be above the water since it's a floating dock. Since the JB will never be in the water, I've always considered a 3R box to be approved for the location.

 

[Jim W in Tampa]

Assuming salt water. If 20 years old i would say it did great. Am sure thru the years it has got soaked many times being where your located. Even a 3r will not last forever. I would find a way to get them above dock.

 

[Bjenks]

Little follow up:

1) I was thinking when I wrote the question that if you could put a box underneath a floating pier surely you could on a fix pier. Further thought makes me realize why you can't for fixed piers versus floating in that you can't control the water level on fixed (thus exposing the box to submersion), but you can on a floating as it floats with the water level. I also got confused between submersible connectors versus approved enclosure (I just assumed that would be a 6P)

2) I now see that the J Box has to be approved by the AHJ so it is up to him on a NEMA 3R or 6P, but keep in mind that a 3R is rain rated and not design for submersion which is what would happen in this case so 6P is the better choice. If walkway mounted then 3R should be fine.

3) I now see that putting the J Boxes under the dock in NEMA 3R enclosures with wet rated connectors is now illegal (not sure if it was 20 years ago). Therefore I have two choices for the customer, put the junction box on the railing in a NEMA 3R box or get the AHJ approval to put a NEMA 6P under the dock with submersible connectors too (kind of a grandfathered solution). I am not sure the cost difference between pulling new wire for the new J Box on the wall versus installing NEMA 6P under the deck and keeping the existing wire.

 

[iMuse97]

Karl,
Is this posted to say you think "submersion" applies to the junction box and not the conductor splices?

Sorry I wasn't clear. The part of the NEC I quoted, 555.9 referred to connections on a floating pier. These connection systems must be listed and rated for submersion and in approved junction boxes. My assumption is that if the splices/connections must be rated for submersion, the box probably ought to be too--but that is for another discussion.

My next comment was short and unclear, too, but I meant to say:

Since OP was working with a fixed pier, all the splicing and must be above. Also, 555.10, specifying the enclosure types, doesn't want the box installation method to diminish the weather-protection-feature of the original rating of the box.

 

[iMuse97]

Little follow up:

1) I was thinking when I wrote the question that if you could put a box underneath a floating pier surely you could on a fix pier. Further thought makes me realize why you can't for fixed piers versus floating in that you can't control the water level on fixed (thus exposing the box to submersion), but you can on a floating as it floats with the water level. I also got confused between submersible connectors versus approved enclosure (I just assumed that would be a 6P)

2) I now see that the J Box has to be approved by the AHJ so it is up to him on a NEMA 3R or 6P, but keep in mind that a 3R is rain rated and not design for submersion which is what would happen in this case so 6P is the better choice. If walkway mounted then 3R should be fine.

3) I now see that putting the J Boxes under the dock in NEMA 3R enclosures with wet rated connectors is now illegal (not sure if it was 20 years ago). Therefore I have two choices for the customer, put the junction box on the railing in a NEMA 3R box or get the AHJ approval to put a NEMA 6P under the dock with submersible connectors too (kind of a grandfathered solution). I am not sure the cost difference between pulling new wire for the new J Box on the wall versus installing NEMA 6P under the deck and keeping the existing wire.

Depending on the location of the marina, I would question the use of 3R as the appropriate above deck box. If there is splashing and waves or boaters hosing down equipment, you may want to go with 4, possibly 4X, if brackish water, etc.