ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

ECN Shout Chat
Top Posters(30 Days)
Admin 17
Recent Posts
Old decora style outlets
by Admin. 03/25/17 11:40 AM
ESA Arc flash course
by TheShockDoctors. 03/24/17 10:15 AM
fuse rejectors
by HotLine1. 03/24/17 07:53 AM
Another Forum Update
by Admin. 03/22/17 03:04 PM
Dining room plugs
by watersparkfalls. 03/21/17 10:31 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
231,496 Are you busy
166,206 Re: Forum
160,653 Need opinion
Who's Online Now
0 registered members (), 53 guests, and 15 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#14619 - 09/25/02 04:03 PM Transformer Overcurrent Protection  
Electra  Offline
Member
Joined: Jul 2002
Posts: 38
Portland, Oregon, USA
My question is concerning transformers over 600V. The sizes of fuse or circuit breaker protection is based off of Table 450-3(a) (1999 Code).

Why is the size of a circuit breaker permitted to be larger than a fuse?

I thought that fuses would offer better performance and therefore be allowed to be rated higher.

I thank you for any guidance you can give me on this.


Work Gear for Electricians and the Trades

#14620 - 09/25/02 08:55 PM Re: Transformer Overcurrent Protection  
Ron  Offline
Member
Joined: Mar 2002
Posts: 582
White Plains, NY
You will find a similar situation for motor short cirucit protection from Table 430.52. Fuses get set tighter to the load than breakers to avoid false trips.


Ron

#14621 - 09/27/02 11:39 AM Re: Transformer Overcurrent Protection  
Electra  Offline
Member
Joined: Jul 2002
Posts: 38
Portland, Oregon, USA
Thank you very much. That makes perfect sense.



Member Spotlight
Bill Addiss
Bill Addiss
NY, USA
Posts: 3,875
Joined: October 2000
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.014s Queries: 14 (0.003s) Memory: 0.7488 MB (Peak: 0.8718 MB) Zlib enabled. Server Time: 2017-03-26 13:07:15 UTC