ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Recent Posts
VFD MotorFeeders
by gfretwell. 10/19/17 01:02 AM
Generator Cable Sizing
by brsele. 10/18/17 07:39 PM
What do you do?
by gfretwell. 10/17/17 01:08 AM
Good ol' copper pipe in the fuse holder trick
by HotLine1. 10/16/17 07:16 PM
Another generator question
by HotLine1. 10/16/17 07:02 PM
New in the Gallery:
Gallery Test
Popular Topics(Views)
241,444 Are you busy
177,423 Re: Forum
169,010 Need opinion
Who's Online Now
0 registered members (), 14 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#171386 - 11/27/07 01:51 AM Marine Shipboard wiring  
sparkyinak  Offline
Member
Joined: Jul 2007
Posts: 1,327
Alaska
I have been looking for the history of switching the neutral at each breaker. Although in most cases, it is not required per IEEE 45, USCG Title 45, and ABS just to name a few, I come across this in older steel vessels. I think it is a relic from the ol' ungrounded days. This would explain I see this in older ships that have been since retrofitted with grounded systems but kept the origional distribution system due to the expense. Can anyone shed actual knowledge on the history?


"Live Awesome!" - Kevin Carosa

Work Gear for Electricians and the Trades

#171394 - 11/27/07 07:58 AM Re: Marine Shipboard wiring [Re: sparkyinak]  
SteveFehr  Offline
Member
Joined: Mar 2005
Posts: 1,213
Chesapeake, VA
Naval ships don't use neutrals, but use 110/63V floating delta, where both terminals in receptacles are hot. The only time the neutral terminals are actually grounded is when fed via isolation transformers or isolated UPS, but that's restricted to very particular applications and done at the equipment, not the panel. This method of distribution lowers the voltage potential (which is important when considering damage control while flooded with saltwater) and increases fault tolerance- you can short out a phase to ground and the system will still work. There are, of course, no ground wires, just bonding to the ship's hull.

So, what you see are 3-phase panels with all "1-phase" circuits fed from 2-pole breakers and ungrounded cables.

Last edited by SteveFehr; 11/27/07 07:59 AM.

#171401 - 11/27/07 11:55 AM Re: Marine Shipboard wiring [Re: SteveFehr]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,123
Estero,Fl,usa
They also have 440 delta for the bigger loads.


Greg Fretwell

#171415 - 11/27/07 06:20 PM Re: Marine Shipboard wiring [Re: gfretwell]  
sparkyinak  Offline
Member
Joined: Jul 2007
Posts: 1,327
Alaska
I am not talking about navel ships but other steel marine vessels. Their AC systems are required to be grounded. Most of the older steel vessels I have encountered are breaking the nuetral at the breaker. All applicable standards state that this is optional, not a requirement. I understand in general why the Navy does what it does but it is not applicable to civilian application


"Live Awesome!" - Kevin Carosa


Member Spotlight
TOOL_5150
TOOL_5150
Bay Area
Posts: 61
Joined: August 2007
Show All Member Profiles 
Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.014s Queries: 15 (0.003s) Memory: 0.7602 MB (Peak: 0.8957 MB) Zlib enabled. Server Time: 2017-10-22 11:54:31 UTC