3 phase power to single phase panel


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Old 01-10-17, 07:54 PM
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3 phase power to single phase panel

I just recently bought a 50x80 shop with 3 phase power coming into a main fused shut off then into old sketchy boxes and wiring, I'm looking to eliminate everything and start over I am experienced with single phase but have never worked with 3 phase my question is is there a way to split off the main 3 phase fuse box to a single phase 100 amp breaker box for my lights and plug ins
 
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Old 01-10-17, 08:45 PM
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Welcome to the forums.

Do you have a voltmeter ?
You need to check from each phase to ground to see what you have there.
 
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Old 01-11-17, 08:58 AM
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In order to replace the main 3 phase fuse box you will need to have the power company shut off the power. Then have them turn the power back on when you finished this job (usually needs a separate permit).

If you keep the existing 3 phase fuse box then you can run single phase from there to your new panel without having the power comany shut off the power. You would run two of the phases and the neutral and a ground line to your new single phase panel.

You need to double check to be sure that the two phases you select each have 120 volts hot to neutral and also you have 208 to 240 volts (no choice as to exact voltage in this range) between the two phases.
 
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Old 01-11-17, 11:03 AM
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Be aware that 3 phase power can have a wild leg
Phase A 120 volts to Grd
Phase B 277V or maybe 240V to Grd
Phase C 120 volts to Grd
Phase to Phase 240V

Be aware also that not all 3 Phase power has a Neutral and can not be used for 120V

Also be aware that it could be 277 volt to Grd, 480 volts Phase to Phase

Another possibility is
Phase A 120V to Grd
Phase B 120V to Grd
Phase C 120V to Grd
Phase to Phase 208 volts

Another possibility is
Phase A 120V to Grd
Phase B 120V to Grd
Phase C 120V to Grd
Phase to Phase 240 volts
 
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Old 01-11-17, 11:52 AM
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One place I worked had 480 star. All single phase came from step down transformers. Check out how any 120 volt receptacles and lights are connected.
 
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Old 01-11-17, 02:53 PM
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T answer your question, after you determine that the voltage is safe to use, select two of the three phases and you have single phase.

All your panels after the main would be sub panels and require four wires, Phase, Phase, Neutral, Ground. Separate Neutral from Ground in all sub panels. A 3 phase sub panel requires five wires.
 
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Old 01-11-17, 04:29 PM
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If you have three phase power available why not keep it. Just tear everything out back to the main disconnect and install a new three phase panel. (Of course check voltages as the others have mentioned) three phase will give you more capacity then single phase and you can still run all your single phase equipment off a three phase panel.
 
 

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