ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Recent Posts
Hello... again!
by HotLine1 - 07/15/24 02:47 PM
90.5(C) Explanatory Material 2023
by gfretwell - 07/15/24 01:19 PM
2023 CEU Course
by renosteinke - 07/12/24 03:26 PM
Counterfeit Code Books?
by Comprehensiveedu - 07/12/24 12:16 PM
Old low volt E10 sockets - supplier or alternative
by gfretwell - 07/11/24 08:51 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
1 members (Scott35), 418 guests, and 14 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Joined: Jul 2002
Posts: 38
Electra Offline OP
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.

Joined: Mar 2002
Posts: 582
Ron Offline
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.

Joined: Jul 2002
Posts: 38
Electra Offline OP
Thank you very much. That makes perfect sense.

Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5