ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
VDE 0100 to introduce AFCIs
by sparky. 01/20/18 05:09 PM
MRI LED lights dimmer control replacement - wow!
by Potseal. 01/19/18 08:52 PM
Video: Inventor of the GFCI self-testing shocks
by Bill Addiss. 01/17/18 11:11 PM
FPE in Germany
by HotLine1. 01/17/18 07:07 PM
Fujifilm Recalls Power Adapter Wall Plugs
by Admin. 01/16/18 07:04 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
1 registered members (gfretwell), 12 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Multiple Motors #4043
09/07/01 09:19 PM
09/07/01 09:19 PM
N
Nevin  Offline OP
Member
Joined: May 2001
Posts: 30
Lititz PA 17543
I am installing 6 identicle pieces of equipment in particular area. Each unit has a 1hp. 460 volt 3phase motor, FLA is 3amps. I have motor starters complete with OL relays set at 3.75 amps on each unit. I am planning on having 1 branch circuit to supply all six units and have a twistlock plug and receptacle at each unit for disconnecting means. According to my calculations a 20 amp circuit would be right, 3amp X 5 units = 15 amps + 3.75 amps for the 6th unit = 18.75 amps (or 20 amps). Am I figuring this right? Also I currently have a 30 amp unused branch circuit at this location. Is there a problem with using that circuit and installing 20amp fuses on each phase before continuing on to my recepts? I know this setup will work, but does anyone know of a safer and/or more practicle way of connecting this equipment?

Work Gear for Electricians and the Trades
Re: Multiple Motors #4044
09/09/01 05:04 AM
09/09/01 05:04 AM
S
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,344
Nevin, check out your math here [Linked Image]

http://necdirect.org/cgi-bin/SoftCa....htm?L+necnonmembers+rwfl8151+1000047299


[This message has been edited by sparky (edited 09-09-2001).]

Re: Multiple Motors #4045
09/09/01 11:03 AM
09/09/01 11:03 AM
Tom  Offline
Member
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
I might be sticking my foot in it here, but if I am, we'll all benefit from it.

I don't feel that this installation would comply with 430-53. Part (a) would require the branch circuit to be protected at not over 15 amps.

Part (b) the smallest rated motor is not protected per 430-52 & table 430-152. 300% x 3 amps = 9 amps which would require 15 amp fuses (see standard sizes 240-6).

You might be able to comply with part (c) or (d), but it would depend on what you're using as a controller.

If all motors don't run at the same time, going to 15 amp fuses looks about right. Otherwise, this installation would have to come into compliance with 430-53(b) or (c) or (d).

Tom

[This message has been edited by Tom (edited 09-09-2001).]


Few things are harder to put up with than the annoyance of a good example.
Re: Multiple Motors #4046
09/09/01 07:42 PM
09/09/01 07:42 PM
N
Nevin  Offline OP
Member
Joined: May 2001
Posts: 30
Lititz PA 17543
So it looks like i have 2 options, 1. to comply with 430-53(a) my branch circuit has to protected with an OCPD of not more then 15 amps. or 2. comply with 430-53(c) having motor controllers with proper listings for group installations etc which would allow me to use a 20 amp circuit (3amps X 6 units = 18amps) next normal size above that = 20 amp circuit.

Re: Multiple Motors #4047
09/11/01 04:05 PM
09/11/01 04:05 PM
Tom  Offline
Member
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
I don't know how much luck you would have with the "marking" part, but the rest of it comes down to a combination starter (built in breaker or switch with fuses). Otherwise, your choices are as you stated them.

Good luck.

Tom


Few things are harder to put up with than the annoyance of a good example.
Re: Multiple Motors #4048
09/12/01 04:57 PM
09/12/01 04:57 PM
Tom  Offline
Member
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
Actually, you have one more choice, but I don't think it changes much. You could call the 20 amp circuit a "feeder", or even leave it as a 30 amp circuit, but you would still need combinations starters with a breaker or set of fuses in them. See part E of article 430.


Few things are harder to put up with than the annoyance of a good example.

Featured:

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

 

Member Spotlight
togol
togol
NW In. USA
Posts: 421
Joined: September 2005
Show All Member Profiles 
Top Posters(30 Days)
Admin 20
sparky 16
Potseal 15
Popular Topics(Views)
243,581 Are you busy
180,379 Re: Forum
170,855 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.017s Queries: 14 (0.003s) Memory: 0.9761 MB (Peak: 1.1167 MB) Zlib enabled. Server Time: 2018-01-21 18:13:22 UTC