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Old 08-27-2013, 02:00 AM   #1
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220 motor on 208


220v 3/4 hp motor ( cannot change voltage) connected to 208v ,,:/ okay I now that it works I've seen it however it also draws more amperage ,I would like to know how to determined the amperage difference.

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Old 08-27-2013, 02:43 AM   #2
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220 motor on 208


You would have to measure it. It is not a linear relationship, and can't be calculated directly. The motor may overheat and will not be able to maintain the full rated load.

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Old 08-27-2013, 01:15 PM   #3
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220 motor on 208


Raul, If you are sizing a circuit for the motor a good rule of thumb is 15% more (220 amp rating x 1.15). Depending on the service factor of your motor and if it is being used at full load the motor may not last but at least the new circuit will support a new 208 motor.
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Old 08-27-2013, 02:03 PM   #4
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220 motor on 208


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Raul, If you are sizing a circuit for the motor a good rule of thumb is 15% more (220 amp rating x 1.15). Depending on the service factor of your motor and if it is being used at full load the motor may not last but at least the new circuit will support a new 208 motor.
Right right thanks guys, good thing this is not my problem but actaully a friend of mine, who just opened a building and all his machines are 220v but the plans marked 120 208 v service now everything is done so I guess he's screwed.
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Old 08-27-2013, 02:04 PM   #5
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220 motor on 208


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Originally Posted by Superrick View Post
Raul, If you are sizing a circuit for the motor a good rule of thumb is 15% more (220 amp rating x 1.15). Depending on the service factor of your motor and if it is being used at full load the motor may not last but at least the new circuit will support a new 208 motor.
Do you mean amps or volts?
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Old 08-27-2013, 02:15 PM   #6
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220 motor on 208


Could always get buck-boost transformer(s) or change the motor.
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Old 08-27-2013, 07:23 PM   #7
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220 motor on 208


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Could always get buck-boost transformer(s) or change the motor.
Thanks man ill make sure to let my buddy know about it, I looked it up on the web after your recommendation ,a 10% buck-boost should do the trick for raising 208 to 229. This is the best fix:D
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Old 08-28-2013, 10:54 AM   #8
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220 motor on 208


Hold on there. Many, many motors are designed to run on 208 volts. In every single case, run the existing motors on 208 until they die.
Then replace with 208/230/460 volt rated motors.

There are motors running today that I installed 15 years ago that were 230 volt motors connected to 208.
I even have several 50 Hz motors still running just as long. 24-7-365 applications.

It really is that simple.
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Old 08-28-2013, 05:49 PM   #9
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220 motor on 208


So the right way would be to go the buckboost way but it could be just as good to just run it the way it is hhhmmmm I guess it all comes down to reliability on the long run , , ⊙_⊙ thanks for the info guys.
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Old 08-28-2013, 06:21 PM   #10
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220 motor on 208


In most cases a 220v motor will run quite happily on 208v.
It will pull a little more current ,about 5% more.
Try it and see !
Unless the motor HP rating is a little light on,
Then it should be fine.
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Old 08-29-2013, 05:52 AM   #11
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220 motor on 208


Quote:
Originally Posted by J. V. View Post
Hold on there. Many, many motors are designed to run on 208 volts. In every single case, run the existing motors on 208 until they die.
Then replace with 208/230/460 volt rated motors.

There are motors running today that I installed 15 years ago that were 230 volt motors connected to 208.
I even have several 50 Hz motors still running just as long. 24-7-365 applications.

It really is that simple.
It's really not that simple. These "machines" were designed/manufactured to perform a specific function, whether to produce a product or to perform a task based on the rated voltage.

Whether it be torque, speed, temperature, or even warranty, etc., the machine may not produce the specified result.

If we were just talking "motor", then maybe it would be that simple but, since we are talking about designed machinery, it may not be that simple.

Having worked in plants most of my career on German, Italian, and European equipment, whenever we consulted the manufacturer on equipment issues, one of the first questions asked was "What voltage are you operating on"?

Just my 2 cents.
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Old 08-29-2013, 07:44 AM   #12
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220 motor on 208


OP really needs his friend to check the voltage specs of each machine. I've just moved and many of my 240v machines are rated for and work ok on 208.
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Old 08-29-2013, 11:12 AM   #13
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Originally Posted by wirenut1110 View Post
It's really not that simple. These "machines" were designed/manufactured to perform a specific function, whether to produce a product or to perform a task based on the rated voltage.

Whether it be torque, speed, temperature, or even warranty, etc., the machine may not produce the specified result.

If we were just talking "motor", then maybe it would be that simple but, since we are talking about designed machinery, it may not be that simple.

Having worked in plants most of my career on German, Italian, and European equipment, whenever we consulted the manufacturer on equipment issues, one of the first questions asked was "What voltage are you operating on"?

Just my 2 cents.
I also have dealt with foreign manufacturers in my career.
99% of the time they are just parroting what they heard in engineering school.
We would ask them what their voltage was, if they were calling us wouldn't we?
Usually they go overboard on everything. They are designed this way. They are engineers. Foreign engineers at that!
I could see one of them loosing sleep over a millivolt difference. While I would sleep like a baby.

I am giving the OP a simple way to address the issue.
I do agree you might give up a tiny fraction of speed since voltage and frequency adjusted proportionality is how you vary ac motor speed.
But it would be a non-factor in most applications. And can be compensated for if required.

I guess we should ask how close the tolerances are in his facility.
If he is enriching uranium for the government, then most likely the specs would not allow these motors to be used as is.

I say run them and see if they perform the task. If they do, continue to run them and in the mean time locate replacements just in case they are needed.
Locate, not purchase.

Chances are very good these motors last long enough that a new guy could come in behind the OP and install the very same 230 volt motors years down the road and never know.

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