ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
220/230/240V 60Hz Systems
by gfretwell. 09/23/18 02:50 PM
Inspection camera help
by petey_c. 09/22/18 07:52 AM
Motion detectors and dimmers
by gfretwell. 09/20/18 04:02 PM
Extension cords
by annemarie1. 09/20/18 08:54 AM
Acronis Backup 2017
by gfretwell. 09/16/18 12:46 AM
New in the Gallery:
Plug terminals
Housebilding DIY wiring
Who's Online Now
0 registered members (), 29 guests, and 24 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Wiring up equipment #487
01/30/01 11:53 AM
01/30/01 11:53 AM
D
doc  Offline OP
Member
Joined: Nov 2000
Posts: 123
Texas
If you have a piece of equipment that is 220 volt single phase,and nameplate of 70 amps, and has a 100 amp breaker installed in the machine,can you hook this up to a 20 amp breaker with # 12 wire,and be legal ? The reason I ask is that is how the machine is wired and it is only used at about 30 second intervals and it stays on,I'm thinking that regardless of if it runs or not you still have to size the breaker and wiring to the machine and not just what works


MAY THE SUN SHINE ON YOUR FACE IN THE MORNING AND YOU AWAKE WITH A SMILE
Work Gear for Electricians and the Trades
Re: Wiring up equipment #488
01/31/01 07:28 AM
01/31/01 07:28 AM
C
cinkerf  Offline
Member
Joined: Dec 2000
Posts: 84
Pittsburgh, Pennsysvania. ...
doc,
It may operate OK but it would not be a legal installation. You must be within the nameplate min. or max. ratings. Of course if it is a single motor with a H.P. rating on nameplate you would have to use NEC Table 430.148 to size circuit breaker and conductors. I hope I was of some help.

cinker (Frank)

Re: Wiring up equipment #489
01/31/01 11:56 AM
01/31/01 11:56 AM
T
therain4  Offline
Member
Joined: Dec 2000
Posts: 38
Dunmore,Pa. U>S.A.
The number 12 is protected at 20 amps per art.240-3(d) but you might want to look at art.670-4(a).I dont know you're circumstance but I dont think you will get to change it if it works as is (been there done that).

Re: Wiring up equipment #490
05/09/01 11:12 AM
05/09/01 11:12 AM
S
SlamTex  Offline
Member
Joined: Apr 2001
Posts: 53
[QUOTE]Originally posted by doc:
[B]If you have a piece of equipment that is 220 volt single phase,and nameplate of 70 amps, and has a 100 amp breaker installed in the machine,can you hook this up to a 20 amp breaker with # 12 wire,and be legal ?

I realize that this is an old post, but I want to address the issue as best that I know how for others who may run into the same situation. If the load is a straight motor load on a branch circuit, the conductors feeding the load must be sized in accordance with 430-22 (which is 125% of the amp rating given in chart 430-148). The OCP for the branch circuit shall be sized in accordance with 430-152. If the equipment has a short time, intermittent, periodic, or varying duty cycle then you may use the chart 430-22(b) for the conductor ampacity. You'll notice that under certain conditions this chart requires that you raise the ampacity of the wire. So bear in mind that just because the equipment is not used for more than 30 seconds that the ampacity of the wire will go up (it may go down). Also remember that a "motor is to be considered to be for continuos duty unless the nature of the apparatus it drives is such that the motor cannot operate continuously with load under any condition of use (1999 NEC Handbook page 468 left side of the page)." Therefore, if there are no control devices that insure that the equipment will not run at full load for 3 hours or more, you must treat the equipment as if it were continuous. There are other issues involved here (110-14 (c), temperature, and others) from a stand point of design, that would be better addressed by an engineer. I won't bore you with the details.


Featured:

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

 

Member Spotlight
HappyElectrician
HappyElectrician
Penn USA
Posts: 31
Joined: December 2011
Show All Member Profiles 
Top Posters(30 Days)
Admin 13
Trumpy 8
Popular Topics(Views)
249,445 Are you busy
187,360 Re: Forum
176,699 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.023s Queries: 14 (0.005s) Memory: 0.9597 MB (Peak: 1.0914 MB) Zlib enabled. Server Time: 2018-09-25 01:23:02 UTC