Service Panel Amperage Question

Reply

  #1  
Old 12-13-06, 01:25 PM
Member
Thread Starter
Join Date: Dec 2006
Posts: 1
Service Panel Amperage Question

I have a general question regarding a service panel. I am looking at my current service panel, which has 200amp service with 20 breakers, each being used. I also have a 100amp subpanel, with 20 available breakers with only 4 being used. My question is this. My main 200amp panel has 20 breakers in it. When I add all of the breakers amp's up, it well exceeds the 200amp limit. Is this a problem? I know this is extremely unlikely, but what would happen if each circuit ran at 90% capacity, resulting in using more than 200amps? I am in process of finishing my basement, and am planning each circuit in my subpanel. Is it safe to use a 20amp fuse for each of the open 16 breakers?
 
Sponsored Links
  #2  
Old 12-13-06, 02:22 PM
HotxxxxxxxOKC's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2006
Location: USA
Posts: 8,044
I'm sure if you run over that 200amp limit, it will trip the breaker, hence the name.
 
  #3  
Old 12-13-06, 02:45 PM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,335
> When I add all of the breakers amp's up, it well exceeds the 200amp limit.
> Is this a problem?

No. There are a few situations where the sum of the breakers is important, but a residential main panel is not one of them.

> I know this is extremely unlikely, but what would happen if each circuit ran
> at 90% capacity, resulting in using more than 200amps?

The main 200A breaker would trip.

> Is it safe to use a 20amp fuse for each of the open 16 breakers?

If you use only #12 wire for the new circuits, yes. I hope you meant breaker, not fuse.
 
  #4  
Old 12-14-06, 10:12 AM
william tell's Avatar
Member
Join Date: Sep 2006
Posts: 176
If you have a 200 main breaker -this means you have 200 amps on each incoming wire on line side of the main for a total of 400 amps available for single pole breakers.

also like ibpooks said it is not a requirement in residential, I'll bet if you put a amp probe on the incoming lines you would'nt even be using half that amount, you do not have something plugged in and running in every recpt. in the home
 
  #5  
Old 12-14-06, 11:03 AM
Member
Join Date: Aug 2004
Location: NA
Posts: 1,065
The diversity of all the loads utilized by the branch circuits generally will be considerably less than the actual sum of the breakers. If every breaker in your main panel was a 20 amp breaker and the panel had 20 slots, then 18 would be for branch circuits leaving that main panel and one double pole for the sub-panel feeder (no tandem single poles) all 18 breakers at 90% would be 324 amps total connected load. Perfectly balanced between both legs on the service would be 162 amps per leg.

Now you also have a sub-panel... the sub-panel will allow whatever the breaker protecting its feeder will permit in amps. If the breaker is a 40 amp double then the sub has 40 amp per leg capabilty. So any load on either hot leg that exceeds 40 amps will eventually trip the breaker. This load is also being pulled thru the 200 amp main breaker in the service panel. So if your four breakers are 20 amp single poles balanced on each leg and they also are at 90% then they would be using 36 amps per leg.

Now this all assumes that all breakers are on at the same time and all are pulling 90% of their rating. Highly unlikely.

At anyrate that would be 162 + 36 = 198 amps ....your 200 main breaker is going to for all practical purposes be maxed out. Your 40 amp feeder breaker to the sub will hold but of course everything is deenergized if the main trips..

Does that answer what your looking for? Remember this is all a bit out in left field but is accurate in the context we are using.

Roger
 

Last edited by Roger; 12-14-06 at 11:42 AM. Reason: Forgot to consider space of sub breaker
Reply

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


Thread Tools
Search this Thread
Display Modes
'