ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
IRC M1307.3
by gfretwell. 08/21/18 08:30 PM
The greenhouse job
by gfretwell. 08/21/18 08:26 PM
Upgrade the old panel
by HotLine1. 08/21/18 08:14 PM
Light Pole Grounding
by HotLine1. 08/20/18 05:34 PM
Calling all Non-US members!! (Non-US only)
by Bill Addiss. 08/13/18 05:52 PM
New in the Gallery:
Plug terminals
Housebilding DIY wiring
Who's Online Now
0 registered members (), 4 guests, and 22 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Transformer fusing #94438
07/29/05 11:18 PM
07/29/05 11:18 PM
G
George Little  Offline OP
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Can someone tell me what the last line of Note 2 to Table 450.3(B) is talking about? The Note 2 for Table 450.3(A) makes sense but not the one for Table (B). 2002 NEC.


George Little
2017 / 2014 NEC & Related Books and Study Guides
Re: Transformer fusing #94439
07/30/05 06:24 AM
07/30/05 06:24 AM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
They are almost identical.

Last sentence of note 2 Table 450.3(A)

"If both circuit breakers and fuses are used as the overcurrent device, the total of the device ratings shall not exceed that allowed for fuses."

Last sentence of note 2 Table 450.3(B)

"If both breakers and fuses are utilized as the overcurrent device, the total of the device ratings shall not exceed that allowed for fuses."

Am I missing something?


[This message has been edited by iwire (edited 07-30-2005).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: Transformer fusing #94440
07/30/05 08:20 AM
07/30/05 08:20 AM
G
George Little  Offline OP
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Yes they are the same Bob, but the difference is Table (A) they give reference to a different % for fuses than for breakers in some cases. In Table (B) they don't differentiate between fuses and breakers???

Maybe I'm missing something??

[This message has been edited by George Little (edited 07-30-2005).]


George Little
Re: Transformer fusing #94441
07/30/05 08:34 AM
07/30/05 08:34 AM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
I get what you are pointing out now. [Linked Image]

I looked in some older NECs and found that as recently as 1996 both tables had separate ratings for fuses and breakers.

The 1999 Table 450-3(b) changed to what we see now.

I guess there was a proposal to change the table but not the notes.

Looks like you could put in a proposal.

You are certainly a careful reader of the NEC. [Linked Image]

Bob

[This message has been edited by iwire (edited 07-30-2005).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: Transformer fusing #94442
08/02/05 06:35 AM
08/02/05 06:35 AM
J
jes  Offline
Member
Joined: Jul 2002
Posts: 103
CT
Hello George,
FYIW, I believe these notes to have nothing to do with the percentages in the tables, just the aggregate sum of the OCP ratings. For example, at smaller OCP values let's say you had 6 devices (for 6 circuits) and a 60 amp single device limit on the xmfr. You could have 6 fuses at 10 amps each. 3 fuses at 10 amps and 3 breakers at 15 amps would not meet the requirement in the note. (10 amps is not a standard breaker rating in 240). You probably can come up with a situation also with motors or another load where the permitted settings for breakers and fuses are different.

Re: Transformer fusing #94443
08/02/05 06:23 PM
08/02/05 06:23 PM
G
George Little  Offline OP
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Okay JES, I can buy into that but there doesn't seem to be any documentation anywhere. Kinda a seldom needed bit of information. Only a Code Geek such as myself would even pursue it [Linked Image]


George Little

Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
electure
electure
Fullerton, CA USA
Posts: 4,271
Joined: December 2000
Show All Member Profiles 
Top Posters(30 Days)
sparky 4
BigB 3
Popular Topics(Views)
248,696 Are you busy
186,432 Re: Forum
175,917 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.017s Queries: 14 (0.004s) Memory: 0.9767 MB (Peak: 1.1235 MB) Zlib enabled. Server Time: 2018-08-22 07:58:08 UTC