Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 05-23-2007, 11:16 PM   #1
Newbie
 
Join Date: May 2007
Posts: 7
Share |
Default

Subpanel over Water


I'm installing a subpanel on the end of a pier to power a 1 hp 240 volt motor and some 120 volt lighting. (Over water)

I plan to bring the power in PVC conduit from my main home (240 feet away) off a 2 pole 50 amp ground fault breaker.

I'll only have two 15 amp breakers in the subpanel (2 pole for the 240 and 1 pole for the lights) My problem is that I only have three #6 aluminum wires feeding the subpanel. (Hot - Hot - Neutral)

My question is can I safely do this with the 3 wires?

And how should I run the neutral? From the main bus in the subpanel to the main bus in my house or to the neutral lug on my ground fault breaker?

JPsAlias is offline   Reply With Quote
Old 05-24-2007, 12:55 AM   #2
Long-Time DIYer
 
Mike Swearingen's Avatar
 
Join Date: Mar 2005
Location: On Albemarle Sound In Northeastern NC
Posts: 1,460
Default

Subpanel over Water


I am not a pro electrician, but I believe that you need to run 3-wire+ground out there (two hots, a neutral and a ground) for what you're trying to do. You can't also have the 120v with just two hots and a ground, which are fine for just the 240v motor. (The lift needs to be GFCI, and the control line probably comes with it.)
I wired my boathouse (a longer distance) from a 20 amp GFCI breaker in the main panel to a sub in the boathouse w/50 amp breaker. I used 8/3wg ul from the main panel to the boathouse, and split it 240v to the boatlift motor, 120v to a lighting circuit and 120v to a receptacle circuit. All is GFCI for an aluminum pontoon boat hanging in steel cables from steel lift pipes w/240v motor, and the outlets and lights. I don't intend to get lit up myself out there. Lightning or a heavy fog can trip it, but better safe than sorry. (I have an electrical contractor friend and he has no GFCI on his boathouse, tho.) Although code calls for wiring to be in conduit, the building inspectors around here don't enforce that out on the sound because the natural heaving and tilting of piers, docks. etc. in freezes and storms would just constantly break it. They do if the water is relatively calm most of the time such as on a river or lake, however.
Good Luck!
Mike

Mike Swearingen is offline   Reply With Quote
Old 05-24-2007, 02:53 AM   #3
Newbie
 
Join Date: May 2007
Posts: 7
Default

Subpanel over Water


Thanks,

Any advice on the conduit when I get to the ramp and float that hindges and subject to boat waves much of the day? Can I submerse the conduit in the water at that point?
JPsAlias is offline   Reply With Quote
Old 05-24-2007, 05:43 AM   #4
Long-Time DIYer
 
Mike Swearingen's Avatar
 
Join Date: Mar 2005
Location: On Albemarle Sound In Northeastern NC
Posts: 1,460
Default

Subpanel over Water


I don't think so. Double-check with your Building Inspector to see if they will even require it in those conditions.
If they do, they will also very likely dictate how it can and cannot be done, I'm sure. In any case, I definitely would use Underground Line, even if it is in conduit.
If they require conduit, I would consider using fexible conduit at a few intervals, with about a 2-3' loop for "give" and I would not secure the rigid sections conduit tightly, but would allow it to slide back and forth in larger size clamps.
The more "give" you can build into it, the less breakage that you will have to deal with. Conduit breakage under a pier/dock is a "when" not an "if". That's why I am very grateful that they don't require it here. I use it above the pier level up into the boathouse and to receptacles up on the beginning of the pier and out up to the dock where the pier and boathouse meet, of course.
You want the least number of j-boxes along the length of it, or far better yet, none at all. A solid continuous piece of electrical UL is best from panel to sub, if possible. It has been my experience that j-boxes under pier and dock sections, even at 5' high above the water level as mine is, will build up condensation inside them no matter how well they are caulked and sealed, which will trip everything. I also use underground electrical connectors with the caulk made into them. There is no such thing as "too much" waterproofing and "prevention" over water.
If they require conduit, see if they will accept a chase made of pressure-treated 1x4s instead. If you use rigid plastic conduit, it is just going to get broken to pieces in every storm.
Good Luck!
Mike

Last edited by Mike Swearingen; 05-24-2007 at 05:48 AM.
Mike Swearingen is offline   Reply With Quote
Old 05-24-2007, 06:45 AM   #5
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,782
Default

Subpanel over Water


You ABSOULTELY cannot run this panel with only a three wire feeder. You need a 4-wire feeder.
Also, #6 at 240' will need to be kept down to 30 or 40 amps. With a heavy load the voltage drop will hurt motors and equipment.

I would secure the conduit to the fixed sections of float. Use liquidtite flexible conduit at the joints.
You do not list a location so it is hard to say, but if your area freezes I would not have the conduit too close to the water. If it does not freeze you can actually have it IN the water if you like.

DO NOT use cable in the conduit. Use individual THHN/THWN conductors. I could also use copper conductors. I am not opposed to aluminum in typical applications but in marine settings I do NOT like AL.
__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.
Speedy Petey is offline   Reply With Quote
Old 05-24-2007, 09:02 PM   #6
Newbie
 
Join Date: May 2007
Posts: 7
Default

Subpanel over Water


My motor only pulls 7 amps. So am I Ok with #6 Aluminum pulling off a 50 amp breaker feeding a 15 amp breaker in the subpanel?

Also, on my fourth wire, will I run from the neural bus in my main panel to the neutral bus in the subpanel. And run the ground from the neutral lug on my ground fault breaker to the neutral bus in the subpanel?
JPsAlias is offline   Reply With Quote
Old 05-24-2007, 09:40 PM   #7
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,782
Default

Subpanel over Water


The 50 amp breaker is fine until you start drawing some more power. Lowering the feeder breaker now will assure this cannot happen.

I am not clear on your other question though.

- The feeder neutral; goes from the neutral/ground bar in the main to the neutral bar in the sub. This bar remains isolated (un-bonded) from the panel enclosure and ground wires.
- The feeder ground; goes from the neutral/ground bar in the main to the ground bar in the sub. This bar IS bonded/attached to the enclosure.
- Grounds and neutrals are kept isolated/separate in the sub-panel.

- The white wire from the GFI breaker goes to the neutral bar in the panel.
- The white wire from the circuit to be protected by the GFI breaker goes to the appropriate connection on the GFI breaker.
__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.
Speedy Petey is offline   Reply With Quote
Old 05-24-2007, 09:44 PM   #8
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,782
Default

Subpanel over Water


Looking back I see the motor is 240v. To protect this with a GFI breaker you connect the two hot wires to the two connections on the GFI breaker. The white lead from the breaker still gets connected to the neutral bar in the panel but there is NO connection to the load side neutral on that breaker. The load neutral is NOT required for the GFI breaker to function properly.
A straight 240v application uses no neutral.
__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.
Speedy Petey is offline   Reply With Quote
Old 05-24-2007, 09:51 PM   #9
Licensed Pro
 
Join Date: Mar 2007
Location: SC
Posts: 1,533
Default

Subpanel over Water


I believe the OP plans to use a GFCI breaker to feed the subpanel. In that case, the white (neutral) will connect to the neutral lug of the GFCI breaker and to the isolated neutral bus in the sub, the GFCI breaker pigtail will connect to the neutral bus in the main, and the ground will connect to the ground bus at each panel.
HouseHelper is offline   Reply With Quote
Old 05-25-2007, 10:37 PM   #10
Newbie
 
Join Date: May 2007
Posts: 7
Default

Subpanel over Water


Thanks for your input guys - I tried to attach the breaker diagram that may clear things up, but it's too large.

So...

With a 240 Ground Fault in the main panel feeding the subpanel:

- The Feeder Hot wires go from the Ground Fault hot lugs to the two hot bus' on the sub.

- The feeder neutral; goes from the neutral lug on the feeder breaker to the neutral bar in the sub. This bar remains isolated (un-bonded) from the panel enclosure and ground wires.

- The feeder ground; goes from the neutral/ground bar in the main to the ground bar in the sub. This bar IS bonded/attached to the enclosure.

- The white wire from the GFI breaker goes to the neutral bar in the main panel.

Am I Ok with a No. 10 wire for the ground? (240 feet from main) Or maybe not pull from the main & drive a ground rod at the river bank (85 feet from the sub)
JPsAlias is offline   Reply With Quote
Old 05-26-2007, 06:46 AM   #11
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,782
Default

Subpanel over Water


I see now. HH was correct about the GFI feeder breaker. Sorry, I didn't read it that way.

Well, basically you have it all correct. The one thing I am not sure about is the grounding electrode (ground rod). I have never been asked for one in an installation such as this, especially that far from the panel. I would ask you AHJ what they think. They would be the ones to make the call.
IF you are required to install one you would need to use #6cu minimum and keep it reasonable protected. If it cannot be protected very well you will need to use #4cu.



You might be well off reading up on NEC ARTICLE 555 Marinas and Boatyards.
This Art. does not cover residential private docks but will give you a good idea of what the intent of the code is.
__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.
Speedy Petey is offline   Reply With Quote
Old 05-28-2007, 06:46 AM   #12
Master Electrician
 
JohnJ0906's Avatar
 
Join Date: Mar 2007
Location: Baltimore, MD
Posts: 332
Default

Subpanel over Water


Personally, I would pole-mount the panel on land, and run circuits individually from panel to the pier. At least this is the way I have always done it. Keeps voltage drop on the main feeder lower, and I can drive a ground rod right next to the panel.

Also, expantion fittings on the pvc might be a good idea, as well as the liquid-tight flex Speedy mentioned. (If you have any long PVC runs)
__________________
John from Baltimore
One Day at a Time
"Experience is what you get when you were expecting something else"
"The bitterness of low quality lingers long after the sweetness of low cost is forgotten"
JohnJ0906 is offline   Reply With Quote
Old 06-05-2007, 09:20 PM   #13
Newbie
 
Join Date: May 2007
Posts: 7
Default

Subpanel over Water


I think I like John's idea of puting the subpanel with ground rod on land at the start of the pier and run the 240 and 120 circuits separately from there. (about 100 feet each to the end of he pier to the boat lift and lighting)

So is number 10 wire good for the 240 volt circuit? (4 wires? Hot, Hot, Neutral, and ground)

Jim
JPsAlias is offline   Reply With Quote
Old 06-05-2007, 10:16 PM   #14
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,782
Default

Subpanel over Water


#12 is fine for that motor. #10 is OK too, just overkill at only 100'.
No, you do NOT need a neutral for a straight 240v motor. Just two hots and a ground.

__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.
Speedy Petey is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Gravity Hot Water Recirculating Loop Questions harleysilo Plumbing 2 02-06-2007 03:28 PM
Water level in boiler system Barefoot Brian HVAC 3 10-19-2006 01:11 PM
Periodic release from (I think) the T&P valve on the water heater alexz Plumbing 3 08-15-2006 10:31 AM
help Chuckman Off Topic 8 06-15-2006 10:06 PM
Draining a hot water heater singforsupper Plumbing 1 06-07-2006 06:01 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.