View Single Post
Old 04-14-2012, 03:59 PM   #102
psneeld
Guru
 
psneeld's Avatar
 
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,146
Quote:
Originally Posted by ksanders View Post
One of the advantages of the main panel-sub panel design is overlapping levels of overcurrent protection, and limiting the areas of an outage due to an equipment failure.

Here's an example...

Lets say that you have a main-sub panel topology in your electrical system. Lets say that you have a 50 amp breaker, feeding 6 awg wire going to a sub panel. At the sub panel you have distribution breakers feeding loads

You have a fault that results in a fail to operate of a distribution breaker (Yes, this happens). The breaker feeding the sub panel will operate. protecting the system from a complete outage and possibly from a fire.

In a ring system, best case scenario is that you generate enough fault current to take down the entire ring. this takes down everything. worsst case you do not have enough fault current to take down the ring. In this case the ring powers the fault current and a fire results.

We haven't even started into the ease of maintaining, ease of fault isolation issues yet.

There are reasons why electrical systems are designed in a star topology, and where they are designed in a ring, they employ very sophisticated protective relay equipment to protect them.
Good points....I may do just that... but I will say that I'm leary of CBs...they work for a dead short...most of the time.. but their failure rate in high amperage situations that aren't dead shorts resulting in hot wires/fires is just to high for my liking. So I'm not sure what I'll do.

Plus, I'm not sure of your example where a fault between a fixture and the sub-panel wouldn't trip a breaker/fuse and who care about the ring circuit unless it dead shorts?
psneeld is online now   Reply With Quote