Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 10-29-2011, 09:23 AM   #16
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Saw struggles, dies


Quote:
Originally Posted by harry_ho View Post
Aw, dang. This guy I used to work with always claimed they'd run better at 240V. Oh well; glad I asked first, anyway.

The blade is practically new. Thin-kerf. Ten-inch. The belt is tensioned by the weight of the motor itself, and the pulley ratio is 1:1.

Maybe the fence has gotten out of square. I'll keep investigating. Thanks, y'all.
Is this a factory built unit?
3000 RPM is pretty low for blade speed. Do your blades have a maximum rated RPM?

a7ecorsair is offline   Reply With Quote
Old 10-29-2011, 09:28 AM   #17
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Saw struggles, dies


Quote:
Originally Posted by harry_ho View Post
It wouldn't be a big deal to pull some #12 if it'll help. The saw sits about eight feet from the panel, but like you say, I'll probe everything with the voltmeter first.

(And right on...that receptacle was indeed back-stabbed)
Do you have room for a two pole breaker? If so, leave the wire in place and change the breaker and convert the motor to 240. Install a 240 15a receptacle.
a7ecorsair is offline   Reply With Quote
Old 10-29-2011, 09:44 AM   #18
Electrical Contractor
 
Join Date: Oct 2011
Location: KC Metro
Posts: 44
Rewards Points: 25
Default

Saw struggles, dies


Your motor will run more efficiently at 240V because there is no return current, therefore it's using all of the power applied. I would wire it up 240V if the option was there.

Last edited by Sine; 10-29-2011 at 09:53 AM.
Sine is offline   Reply With Quote
Old 10-29-2011, 09:47 AM   #19
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Saw struggles, dies


Quote:
Originally Posted by Sine View Post
Your motor will run more efficiently at 240V because there is no return current, therefore it using all of the power applied. I would wire it up 240V if the option was there.
Huh, no return current?
a7ecorsair is offline   Reply With Quote
Old 10-29-2011, 09:53 AM   #20
Member
 
Join Date: Mar 2007
Location: Eighty Four, Pa.15330
Posts: 1,332
Rewards Points: 662
Default

Saw struggles, dies


Watts is Watts.
bobelectric is offline   Reply With Quote
Old 10-29-2011, 10:06 AM   #21
Electrical Contractor
 
Join Date: Oct 2011
Location: KC Metro
Posts: 44
Rewards Points: 25
Default

Saw struggles, dies


Quote:
Originally Posted by a7ecorsair View Post
Huh, no return current?
No return current to ground, am I wrong?
Sine is offline   Reply With Quote
Old 10-29-2011, 10:18 AM   #22
Electrical Contractor
 
Join Date: Oct 2011
Location: KC Metro
Posts: 44
Rewards Points: 25
Default

Saw struggles, dies


Quote:
Originally Posted by bobelectric View Post
Watts is Watts.
Very true but the higher the voltage or force the less it struggles at start up and under heavy load.
Sine is offline   Reply With Quote
Old 10-29-2011, 10:22 AM   #23
JOATMON
 
ddawg16's Avatar
 
Join Date: Aug 2011
Location: S. California
Posts: 7,568
Rewards Points: 2,466
Default

Saw struggles, dies


Quote:
Originally Posted by Sine View Post
Your motor will run more efficiently at 240V because there is no return current, therefore it's using all of the power applied. I would wire it up 240V if the option was there.
Quote:
Originally Posted by Sine View Post
No return current to ground, am I wrong?
To some extent....yes.

There should never be any return current to ground.....that would be a ground fault....it should be to the neutral or other hot leg.

In a 120Vac setup, the return path is via the neutral.

In a 240Vac setup, the return path is via the other hot....

As noted in frequent threads....watts is watts. The only real advantage of 240Vac is that you can use smaller wire or get more power through the existing wire....i.e., the voltage drop is less.

If you look at the motor wiring....when you change the wireing between 120/240....in 120 mode, the poles are in series....in 240 mode, parallel. Hence, the actual current flowing through the windings is the same in either mode.
__________________
Even if you are on the right track, you will still get run over if you just sit there.

My 2-Story Addition Build in Progress Link ... My Garage Build Link and My Jeep Build Link
ddawg16 is offline   Reply With Quote
Old 10-29-2011, 11:36 AM   #24
Electrical Contractor
 
Join Date: Oct 2011
Location: KC Metro
Posts: 44
Rewards Points: 25
Default

Saw struggles, dies


[QUOTE=ddawg16;759278]To some extent....yes.

There should never be any return current to ground.....that would be a ground fault....it should be to the neutral or other hot leg.

In a 120Vac setup, the return path is via the neutral.

The neutral is a grounded conductor.
Sine is offline   Reply With Quote
Old 10-29-2011, 11:55 AM   #25
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Saw struggles, dies


[quote=Sine;759333]
Quote:
Originally Posted by ddawg16 View Post
The neutral is a grounded conductor.
This is correct.
It is a conductor; it is not ground.
a7ecorsair is offline   Reply With Quote
Old 10-29-2011, 12:21 PM   #26
Electrical Contractor
 
Join Date: Oct 2011
Location: KC Metro
Posts: 44
Rewards Points: 25
Default

Saw struggles, dies


[QUOTE=a7ecorsair;759352]
Quote:
Originally Posted by Sine View Post
This is correct.
It is a conductor; it is not ground.
I am well aware it is not ground, but it is a "grounded conductor" as opposed to an "ungrounded conductor".
Sine is offline   Reply With Quote
Old 10-29-2011, 12:26 PM   #27
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Saw struggles, dies


[quote=Sine;759382]
Quote:
Originally Posted by a7ecorsair View Post

I am well aware it is not ground, but it is a "grounded conductor" as opposed to an "ungrounded conductor".
And therefore provides return current to the transformer centertap.
a7ecorsair is offline   Reply With Quote
Old 10-29-2011, 12:55 PM   #28
Electrical Contractor
 
Join Date: Oct 2011
Location: KC Metro
Posts: 44
Rewards Points: 25
Default

Saw struggles, dies


[QUOTE=a7ecorsair;759385]
Quote:
Originally Posted by Sine View Post
And therefore provides return current to the transformer centertap.
Correct, my point was that it was a grounded conductor not just a conductor
Sine is offline   Reply With Quote
Old 10-29-2011, 01:28 PM   #29
Member
 
Join Date: Feb 2010
Location: MI's Western UP
Posts: 599
Rewards Points: 500
Default

Saw struggles, dies


jumping to 240 volts will halve the current draw and should work with your puny wires much better. The only downside I see is you might have a hard time getting a 15 amp double pole breaker.
forresth is offline   Reply With Quote
Old 10-29-2011, 01:39 PM   #30
Idiot Emeritus
 
Join Date: Mar 2008
Location: Fernley, Nevada (near Reno)
Posts: 1,625
Rewards Points: 1,044
Default

Saw struggles, dies


Quote:
Originally Posted by harry_ho View Post
Okay...the motor is what it is and will never be anything else; I get that. But what's the deal with this "thermal protection?" I keep thinking less amperage generates less heat and won't blow the little red button off as soon...or am I heading toward fantasy land again?

I obviously need to read up some more about motors.
Thermal protection on a motor is nothing more than an extremely accurate circuit breaker.

As the load on a motor goes up, so does its current. When the current gets too high, the thermal will see it and trip, thus stopping current flow altogether.

A dual voltage motor is basically two single voltage motors in the same frame. In your case, it's two 3/4HP 120 volt motors. When they're connected in parallel, each one needs 120 volts and 6.5 amps, for a total of 13 amps. When they're in series, each one still needs 120 volts and 6.5 amps, but now the voltage is 240 and the current is 6.5 amps.

Since the current will be very close to the same in either winding, regardless of series or parallel connection, the thermal senses current on only one of the windings. But it cuts current off to both windings. This is why the brown lead is not used for the high voltage (series) connection. In series, there is only one circuit to cut off. In parallel, there are two.

If it were me, I would certainly re-connect the motor for 240, leave the 14/2 in place, get a 15 amp 240 receptacle and plug, and connect it to a 15 amp two-pole breaker.

True enough, this motor will produce its rated HP at either voltage, but at 240 it'll produce more HP before it bogs down.

micromind is online now   Reply With Quote
The Following User Says Thank You to micromind For This Useful Post:
harry_ho (10-29-2011)
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Lawn Mower starts for two seconds then dies guaps Landscaping & Lawn Care 36 11-10-2013 12:27 PM
Honda 160cm3 self prop. lawn mower dies notahandyman Landscaping & Lawn Care 4 09-28-2010 10:12 PM
AC capacitor dies siliconfiber HVAC 6 06-16-2009 11:15 PM
A/C struggles in hot weather kennelm HVAC 24 04-10-2009 09:33 PM
Engine Slowly Loses Power and Dies While Driving slickshift Automotive Repairs 16 01-15-2007 12:34 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.