208/460 Motor Very HOT! - 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 Forum > General Electrical Discussion


Like Tree8Likes
  • 1 Post By wildleg
  • 3 Post By tates1882
  • 2 Post By 460 Delta
  • 2 Post By micromind
Reply
 
Thread Tools Display Modes
Old 09-06-2019, 12:50 PM   #1
Junior Member
 
Join Date: Sep 2019
Posts: 2
Rewards Points: 4
Default 208/460 Motor Very HOT!

Couldn't figure out a title, but help me out on this one.

Baldor 7.5hp (6 years old), Cooling finds, fan blade intact, FLA is 19.5/9.5 (208-230/460). The motor under no load was drawing 8.0, 8.1, 8.3 Amps and was very hot from cool to running for 15 minutes. Would eventually trip a breaker set at 18amps.

A new motor was installed same specs FLA 20/10 (208-230/460) and is cool as can be after 15 minutes.

The other motor had a slight hum any thoughts? Bearings over time expanding binding? I never saw it trip, but did feel the temperature you could not put your hand on it for more than 1-1.5 seconds.
jasil 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 09-06-2019, 12:58 PM   #2
animal lover /rat bastard
 
wildleg's Avatar
 
Join Date: Apr 2009
Location: somewhere in FL
Posts: 13,547
Rewards Points: 1,038
Default

cool .
glen1971 likes this.
__________________
this message was sent from a dental floss farm using ZappaTalk and a pair of zirconium encrusted tweasers
wildleg is offline   Reply With Quote
Old 09-06-2019, 02:35 PM   #3
zap
 
tates1882's Avatar
 
Join Date: Sep 2010
Location: northwest
Posts: 1,299
Rewards Points: 1,040
Default

Your hand isn't a accurate thermometer, Sounds like it was single phasing.

Last edited by tates1882; 09-06-2019 at 02:41 PM.
tates1882 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 09-06-2019, 02:49 PM   #4
Junior Member
 
Join Date: Sep 2019
Posts: 2
Rewards Points: 4
Default

Okay great answers! Strange place this Electrician Talk .com

Has anyone ever seen single phasing that is not picked by a clamp on Amp meter?
jasil is offline   Reply With Quote
Old 09-06-2019, 02:51 PM   #5
Senior Member
 
Join Date: May 2018
Location: florida
Posts: 1,497
Rewards Points: 1,214
Default

Quote:
Originally Posted by jasil View Post
Couldn't figure out a title, but help me out on this one.

Baldor 7.5hp (6 years old), Cooling finds, fan blade intact, FLA is 19.5/9.5 (208-230/460). The motor under no load was drawing 8.0, 8.1, 8.3 Amps and was very hot from cool to running for 15 minutes. Would eventually trip a breaker set at 18amps.

A new motor was installed same specs FLA 20/10 (208-230/460) and is cool as can be after 15 minutes.

The other motor had a slight hum any thoughts? Bearings over time expanding binding? I never saw it trip, but did feel the temperature you could not put your hand on it for more than 1-1.5 seconds.
presuming you are running the motor on 480v as you have a 18 amp breaker setting then no load should have been around 5-6 amps and you are showing 8amps. (if you tested the new motor with new load it should be around 50-60% of FLA)

Best guess is the motor has a bad bearing causing 3 amps of load (the phases are balanced so that counts out alot of different problems).
As the bearing gets hotter the tighter the tolerances the more load applied thus causing more heat rinse and repeat until the motor safetys kick in.

Are you sure its the breaker kicking at 18amps and not the Overload block.

I would suggest reading and understanding how to calculate and set your motor safety's including service factor. Caught early with the correct motor protection settings this could have been a quick bearing change rather than a motor replacement.
gpop is online now   Reply With Quote
Old 09-06-2019, 03:22 PM   #6
zap
 
tates1882's Avatar
 
Join Date: Sep 2010
Location: northwest
Posts: 1,299
Rewards Points: 1,040
Default

Quote:
Originally Posted by jasil View Post
Okay great answers! Strange place this Electrician Talk .com
Its not exactly clear if you are in fact a professional electrician, so normally if you fail to fill out your profile than most members won't answer until you are vetted or a mod boots you.
micromind, glen1971 and Bird dog like this.
tates1882 is offline   Reply With Quote
Old 09-07-2019, 01:30 AM   #7
Senior Member
 
Join Date: Dec 2010
Location: So.Cal.
Posts: 3,559
Rewards Points: 7,057
Default

When was the last time the oil was checked? Depending on bearing type, the right oil is important. Does it turn freely? No grinding?
__________________
-------------------------------
~ She thinks I'm crazy, but I'm just growing old~
joebanana is offline   Reply With Quote
Old 09-07-2019, 07:30 AM   #8
Senior Member
 
460 Delta's Avatar
 
Join Date: May 2018
Location: Southern Ohio
Posts: 805
Rewards Points: 956
Default

When run on the low voltage connection, a motor can be partially single phased if one of the paralleled winding connections comes loose or opens up leaving only half the winding to take the load. They will be noisier than usual and run hotter than normal if this happens.
micromind and JRaef like this.
__________________
Perfection is the enemy of good enough
460 Delta is offline   Reply With Quote
Old 09-07-2019, 05:45 PM   #9
Member
 
Join Date: Aug 2019
Posts: 80
Rewards Points: 160
Default John R retired electrician from Fed Gov

Quote:
Originally Posted by jasil View Post
Couldn't figure out a title, but help me out on this one.

Baldor 7.5hp (6 years old), Cooling finds, fan blade intact, FLA is 19.5/9.5 (208-230/460). The motor under no load was drawing 8.0, 8.1, 8.3 Amps and was very hot from cool to running for 15 minutes. Would eventually trip a breaker set at 18amps.

A new motor was installed same specs FLA 20/10 (208-230/460) and is cool as can be after 15 minutes.

The other motor had a slight hum any thoughts? Bearings over time expanding binding? I never saw it trip, but did feel the temperature you could not put your hand on it for more than 1-1.5 seconds.
I am old school, to hot to touch, something wrong, bearing would be my guess
John R is offline   Reply With Quote
Old 09-07-2019, 08:17 PM   #10
Bilge Rat
 
Join Date: Aug 2007
Location: Fernley, Nevada (near Reno)
Posts: 6,583
Rewards Points: 2,776
Default

I looked up the specs for a basic Baldor 7.5 HP 4 pole TEFC 213T steel frame motor, model EM3710T.

It states that the full-load temperature rise is 63C (145F). And that's over and above ambient. If ambient is 40C (104F), then its winding temperature would be somewhere around 103C (217F). The frame would be cooler but still pretty pickin hot! But also normal for this motor.

It has class F insulation, this means that the hottest part of the windings can safely operate at 155C (311F). Again, the frame will be cooler than this but it shows that it can indeed run way hotter than you'd think is normal.

A Leeson model 140450 (same type) is 43C (109F), same as a Marathon E2116.

A Lincoln model LM32805 has a 55C (131F).
tates1882 and gpop like this.
micromind is offline   Reply With Quote
Old 09-09-2019, 01:26 AM   #11
Senior Member
 
Join Date: Jun 2010
Location: Brisbane, Australia.
Posts: 2,888
Rewards Points: 2,410
Default

shorted turns in the field.
dmxtothemax is online now   Reply With Quote
Old 09-09-2019, 02:31 PM   #12
Senior Member
 
JRaef's Avatar
 
Join Date: Mar 2009
Location: SF Bay Area, California
Posts: 5,111
Rewards Points: 2,106
Default

Quote:
Originally Posted by 460 Delta View Post
When run on the low voltage connection, a motor can be partially single phased if one of the paralleled winding connections comes loose or opens up leaving only half the winding to take the load. They will be noisier than usual and run hotter than normal if this happens.
The trick to finding this is to measure all three phase currents and compare them. A small difference in current results in a very large difference in motor heat, because when a winding is not being fed power, it becomes a generator creating "negative sequence current" which then makes a rotating magnetic field then opposes the direction of the motor rotation, so the rest of the motor has to "fight" that one partially dead winding.
__________________
"If you don't know where you're going, then any direction will do." -- Lewis Carroll
JRaef is offline   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



All times are GMT -4. The time now is 03:33 AM.


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