ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
GFCI's pops in large numbers
by dsk - 10/21/21 02:03 AM
Need some info on Japanese outlets, 200V 15A
by andey - 10/20/21 08:05 AM
Wire sizing
by watersparkfalls - 10/19/21 07:27 AM
nec 110.3 (B)
by watersparkfalls - 10/19/21 07:09 AM
A 5-20(20a) receptacle is legal on a 15a circuit?
by libellis - 10/10/21 12:46 PM
New in the Gallery:
240/208 to a house
240/208 to a house
by wa2ise, October 9
Now you know.
Now you know.
by Tom_Horne, September 7
Who's Online Now
0 members (), 8 guests, and 17 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#171386 11/27/07 01:51 AM
Joined: Jul 2007
Posts: 1,335
S
Member
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
Joined: Mar 2005
Posts: 1,213
S
Member
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.
Joined: Jul 2004
Posts: 9,667
Likes: 6
G
Member
They also have 440 delta for the bigger loads.


Greg Fretwell
Joined: Jul 2007
Posts: 1,335
S
Member
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

Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
togol
togol
NW In. USA
Posts: 421
Joined: September 2005
Top Posters(30 Days)
dsk 6
Popular Topics(Views)
284,715 Are you busy
217,341 Re: Forum
203,693 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5