NEMA 2 starter sizing - Electrician Talk - Professional Electrical Contractors Forum
CLICK HERE AND JOIN OUR COMMUNITY TODAY, IT'S FREE!
Go Back   Electrician Talk - Professional Electrical Contractors Forum > Electrical Trade Topics > Industrial Electrical Forum


Like Tree4Likes
  • 1 Post By bill39
  • 1 Post By 460 Delta
  • 1 Post By 460 Delta
  • 1 Post By frenchelectrican
Reply
 
Thread Tools Display Modes
Old 05-20-2019, 04:42 PM   #1
Senior Member
 
460 Delta's Avatar
 
Join Date: May 2018
Location: Southern Ohio
Posts: 542
Rewards Points: 474
Default NEMA 2 starter sizing

At what point or time did manufacturers derate size 2’s to 10hp on a 200 volt system? I’ve some Citations that are 15hp and maybe newer ones that derate them to 10hp, it’s something that I’ve noticed in the last few years and I’m wondering why and when.
__________________
Perfection is the enemy of good enough
460 Delta is offline   Reply With Quote
Join Contractor Talk

Join the #1 Electrician Forum Today - It's Totally Free!

ElectricianTalk.com - Are you a Professional Electrical Contractor? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's the leading place for electricians to meet online. No homeowners asking DIY questions. Just fellow tradesmen who enjoy talking about their business, their trade, and anything else that comes up. No matter what your specialty is you'll find that ElectricianTalk.com is a great community to join. Best of all it's totally free!

Join ElectricianTalk.com - Click Here JOIN FOR FREE


Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ElectricianTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

Sponsored Links
Advertisement
 
Old 05-20-2019, 07:48 PM   #2
Modrateur
 
frenchelectrican's Avatar
 
Join Date: Mar 2007
Location: Philippines
Posts: 8,512
Rewards Points: 16,534
Default

Quote:
Originally Posted by 460 Delta View Post
At what point or time did manufacturers derate size 2’s to 10hp on a 200 volt system? I’ve some Citations that are 15hp and maybe newer ones that derate them to 10hp, it’s something that I’ve noticed in the last few years and I’m wondering why and when.
If I remember correct it was on the borderline on limit rating on contractors and it been that way for last 15 years or so

If ran on 230 volts then 15 Hp will work just fine on size 2 starter without much issue.

with air compressor 15 HP at 200 volt system could take size two starter but right on the limit of rating so typically I go with size 3 or 2 1/2 if I can find it.

Just dont mention IEC stuff that is worst than NEMA verison is.
__________________
Bleu est beau.
frenchelectrican is online now   Reply With Quote
Old 05-20-2019, 08:58 PM   #3
Bilge Rat
 
Join Date: Aug 2007
Location: Fernley, Nevada (near Reno)
Posts: 6,340
Rewards Points: 2,292
Default

I don't know when they changed the ratings but I do know this.....the HP ratings of NEMA starters make no sense at all to me.
micromind is online now   Reply With Quote
Sponsored Links
Advertisement
 
Old 05-20-2019, 09:03 PM   #4
Senior Member
 
Join Date: Sep 2009
Location: Midwest
Posts: 843
Rewards Points: 1,448
Default

Quote:
Originally Posted by micromind View Post
I don't know when they changed the ratings but I do know this.....the HP ratings of NEMA starters make no sense at all to me.
Just curious: do you think NEMA ratings are too conservative?

It’s not something I ever put much thought into. Kinda like fighting city hall, you can’t win.
micromind likes this.
bill39 is online now   Reply With Quote
Old 05-20-2019, 09:27 PM   #5
Senior Member
 
460 Delta's Avatar
 
Join Date: May 2018
Location: Southern Ohio
Posts: 542
Rewards Points: 474
Default

Quote:
Originally Posted by micromind View Post
I don't know when they changed the ratings but I do know this.....the HP ratings of NEMA starters make no sense at all to me.
What part makes no sense? I always thought it was a simple intuitive system made for us front line electricians.
I suppose my question was when and why did they get more conservative on their ratings?
I understand that 200 volt motors pull more current, but I didn’t think it would make a derate necessary.
micromind likes this.
__________________
Perfection is the enemy of good enough
460 Delta is offline   Reply With Quote
Old 05-20-2019, 10:57 PM   #6
Bilge Rat
 
Join Date: Aug 2007
Location: Fernley, Nevada (near Reno)
Posts: 6,340
Rewards Points: 2,292
Default

It's the HP ratings vs. the max current ratings.

For example, a size 4 is good for 50HP @230 volts, 100 HP @ 460 volts and 135 amps. This makes sense

A size 1 however is good for 7 1/2 HP @ 230 but only 10 HP @ 460. It can handle 27 amps. Why not 15 HP @ 460. This doesn't make any sense at all. A 15 HP motor on 460 volts draws a lot less that 27 amps. It's even good for 7 1/2 HP @ 200 volts. Why only 10 HP @ 460?
micromind is online now   Reply With Quote
Old 05-21-2019, 05:12 AM   #7
Senior Member
 
460 Delta's Avatar
 
Join Date: May 2018
Location: Southern Ohio
Posts: 542
Rewards Points: 474
Default

Quote:
Originally Posted by micromind View Post
It's the HP ratings vs. the max current ratings.

For example, a size 4 is good for 50HP @230 volts, 100 HP @ 460 volts and 135 amps. This makes sense

A size 1 however is good for 7 1/2 HP @ 230 but only 10 HP @ 460. It can handle 27 amps. Why not 15 HP @ 460. This doesn't make any sense at all. A 15 HP motor on 460 volts draws a lot less that 27 amps. It's even good for 7 1/2 HP @ 200 volts. Why only 10 HP @ 460?
I was always told [true or not] it was because the arc is harder to interrupt at higher voltages and the lower current [lower hp] was necessary to make it possible.
I always had the same thoughts as a younger man, but the explanation made sense in that opening the contacts on a fully loaded 15hp motor on a 460 volt system would tax the abilities of a size 1 to quench the arc.
With the larger sizes, I suppose the arc quench is there because at that size people aren't after compactness, or weight reduction, just function.
micromind likes this.
__________________
Perfection is the enemy of good enough
460 Delta is offline   Reply With Quote
Old 05-21-2019, 06:16 PM   #8
Modrateur
 
frenchelectrican's Avatar
 
Join Date: Mar 2007
Location: Philippines
Posts: 8,512
Rewards Points: 16,534
Default

Quote:
Originally Posted by 460 Delta View Post
I was always told [true or not] it was because the arc is harder to interrupt at higher voltages and the lower current [lower hp] was necessary to make it possible.
I always had the same thoughts as a younger man, but the explanation made sense in that opening the contacts on a fully loaded 15hp motor on a 460 volt system would tax the abilities of a size 1 to quench the arc.
With the larger sizes, I suppose the arc quench is there because at that size people aren't after compactness, or weight reduction, just function.
That what I heard and confirm that part espceally with smaller units the issue is arc surpession that is the key issue but being on 200 volts that kinda puzzle me a little.
micromind likes this.
__________________
Bleu est beau.
frenchelectrican is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Difference between weatherproof and waterproof enclosure haiderster General Electrical Discussion 10 05-01-2019 05:03 PM
Cletus Question......NEMA Starters micromind PLCs, VFDs, Motors and Controls 19 01-24-2018 07:35 PM
Bi-metallic O/Ls. micromind PLCs, VFDs, Motors and Controls 12 12-27-2017 06:47 PM
For Sale Nema Size 3 Allen Bradley Starter lightman Electrician Swap 12 06-30-2017 01:05 PM
Motor Higher HP Than Starter Rating micromind PLCs, VFDs, Motors and Controls 11 01-22-2017 11:10 PM


All times are GMT -4. The time now is 08:17 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com