Converting 230 3 phase to 120/208

[flip]

My area is converting from 230 volt 3 phase to 120/208 volt on all its existing and operating industrial buildings. We still have 480 but the 230 volt is being changed just on the utility side. I personally believe 120/208 is for commercial use and not for machine shops and other production facilities. Anybody else agree?? Do you see the downfalls as I do or am I all washed up??

Thanks guys.

 

[augie47]

Re: Converting 230 3 phase to 120/208

personally, I think there is some validity to your point. 208/120 would be more suitable to a commercial facility with a heavy 120 volt load, such as lighting, than to a machine shop.
A lot of your equipment may not be affected, some motors aren't that particular. Any equipment that has heating capability will certainly be affected,

 

[bob]

Re: Converting 230 3 phase to 120/208

My area is converting from 230 volt 3 phase to 120/208 volt on all its existing and operating industrial buildings

Are you referring to your area of the plant or your area of town? If you have any say, I would suggest you convert to a 277/480 volt system.

 

[flip]

Re: Converting 230 3 phase to 120/208

We are a government installation. We have approximately 10 production facilities. They are changing out our transformer banks at our buildings and alot of the equipment in place is not rated 208.

Bad Idea to me!!

 

[tom baker]

Re: Converting 230 3 phase to 120/208

The nominal voltage is 120/240, not 230. Its a violation to use equipment rated for a 240 volt system at 208 volts, per 110.3(B)
l voltage of a circuit to which it is connected.

Your motors will draw excessive current as they will operating at 10% under voltage. Resistive loads will not put out the rated power.

 

[bob]

Re: Converting 230 3 phase to 120/208

Another point is that if the motors are rated at
240 volts, 10% tolerance = 24 volts. 240 - 24 = 216 volts. You are starting with 208 volts without considering the voltage drop. The torque of the motors will decrease about 20%. Suggest you try to sell 277/480 volts.

 

[bdarnell]

Re: Converting 230 3 phase to 120/208

Originally posted by tom baker:
Its a violation to use equipment rated for a 240 volt system at 208 volts, per 110.3(B)

Tom:

Where does it say that ? I read 110.3(B) and it mentions nothing about voltage. 110.4 adresses voltage, but it says equipment can not be rated less that the voltage applied, not the other way round.

Am I wrong on this ? It may be a moot point since most polyphase motors are rated 208-230/460 anyway.

 

[charlie b]

Re: Converting 230 3 phase to 120/208

Originally posted by bdarnell: I read 110.3(B) and it mentions nothing about voltage.

I believe Tom's point is that if you supply a motor with a voltage level that is outside the range of the voltages for which it is rated, then you will not be operating it in accordance with the instructions of its listing. That is how this is a violation of 110.3(B).

Originally posted by bdarnell: It may be a moot point since most polyphase motors are rated 208-230/460 anyway.

If the motors in your facility are in fact rated for 208 ? 230, then you may supply them at 208 (even though there will be a voltage drop from a source that supplies 208), and you will still be operating it in accordance with the instructions of its listing.

 

[tom baker]

Re: Converting 230 3 phase to 120/208

110.3B does not have to address voltage. It says you follow the mfg instructions. If the equipment is 230v listed (only) then its a violation on a 200 v system. New equipment is often labled for 230/200 V use.

 

[flip]

Re: Converting 230 3 phase to 120/208

we were 230 volt delta not 120/240.