1 Phase To Vfd To 3 Phase...neutral/ground Wire Confusion

coolidge

coolidge

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Input - single phase 220 vac 30 amp breaker at my service panel. I originally had this wired to the VFD with just 3 wires, Black HOT, White HOT, Green, simple.

Then I got it in my head to re-wire it using 4 wire Black HOT, Red HOT, White Neutral, Green so that I could tap one of the hots and the White Neutral for a 120 vac service at the mill. I read that's the proper way to do this, that there is the potential for the White Neutral to have voltage on it when used for 120 vac service thus you need a 4th wire for the ground.

So should I use the Green ground wire for all grounding, VFD, Motor ground lug, electrical cabinet, etc. and only use the White neutral wire for the 120 vac service?
 
The short answer is YES! While the ground would work as a Neutral or vice-virsa, the proper way to do it is as you described.
 
Industry standard 110 volt AC power
White is AC return also should be electrically at the same potential as the green ground (but different path) also can be tied in to the secondary circuit as AC return
black hot example... used for a sealing FAN LIGHT
red secondary hot example... used for a sealing FAN
green (safety ground) should be hooked to copper rod by circuit breaker box ..and electrically connected to outside of equipment motor housing in case one of the hot short out (this should blow the breaker)... if your lucky

Looking at a plug in the wall LARGE blade is the white wire , SMALL blade is the hot , and BOTTOM MIDDLE round is the green safety ground.

Note: All bets are off.. if not wired by a certified electrician originally and be very careful

Hopefully, I make this clear as mud BUT... If you don't believe me look it up on the internet
PS: I don't really know how electricity works .. I Just know it calms me.

Dawner
 
No! you cannot use the green ground wire for a neutral! NEVER! They must stay separate through out the entire circuit.

The only place they can be connected together is at the meter box. At that point, they are connected together to both the earth ground wire from the ground rod and the ground from the overhead wire coming from the pole. And if the breaker box is metallically attached to the meter box, both the grounds and neutrals of all incoming circuits can share the same bonding strip in the breaker box. If the breaker box is a branch circuit from the main breaker box, it must have a separate bonding strip installed for all ground wires to be attached. All neutrals must be installed to the other bonding strip WITHOUT the bonding screw installed to ground.

I have been shocked from neutrals that were not installed properly and were bonded to the ground before! Play it safe, and do it correct. Hire an electrician! And shame on the electrician if he doesn't do it correctly!
 
Relax the green ground wire is not used for neutral. All 120 vac items (relays, fan) use black (Hot) and white (neutral). Where a ground is required for safety in case of a short circuit (fan housing, electrical cabinet, motor housing, VFD cabinet) the green wire is used.
 
4gsr said:
No! you cannot use the green ground wire for a neutral! NEVER! They must stay separate through out the entire circuit.
Click to expand...

I agree.

I should have noted in my post above that while the Neutral and the Ground are bonded together at come point (exactly where depends on whether you have a 3 or 4 wire system) and the ground would electrically work as a neutral, NEVER use the ground as a current carrying conductor. It is only a safety conductor.
 
Yea, it would help if I had gone back and re-read the original question......
 
4gsr said:
No! you cannot use the green ground wire for a neutral! NEVER! They must stay separate through out the entire circuit.

The only place they can be connected together is at the meter box. At that point, they are connected together to both the earth ground wire from the ground rod and the ground from the overhead wire coming from the pole. And if the breaker box is metallically attached to the meter box, both the grounds and neutrals of all incoming circuits can share the same bonding strip in the breaker box. If the breaker box is a branch circuit from the main breaker box, it must have a separate bonding strip installed for all ground wires to be attached. All neutrals must be installed to the other bonding strip WITHOUT the bonding screw installed to ground.

I have been shocked from neutrals that were not installed properly and were bonded to the ground before! Play it safe, and do it correct. Hire an electrician! And shame on the electrician if he doesn't do it correctly!
Click to expand...
guess i wasn't clear enough ... my bad
 
Dawner said:
Industry standard 110 volt AC power
White is AC return also should be electrically at the same potential as the green ground (but different path) also can be tied in to the secondary circuit as AC return
black hot example... used for a sealing FAN LIGHT
red secondary hot example... used for a sealing FAN
green (safety ground) should be hooked to copper rod by circuit breaker box ..and electrically connected to outside of equipment motor housing in case one of the hot short out (this should blow the breaker)... if your lucky

Looking at a plug in the wall LARGE blade is the white wire , SMALL blade is the hot , and BOTTOM MIDDLE round is the green safety ground.

Note: All bets are off.. if not wired by a certified electrician originally and be very careful

Hopefully, I make this clear as mud BUT... If you don't believe me look it up on the internet
PS: I don't really know how electricity works .. I Just know it calms me.

Dawner
Click to expand...
White is AC return..... Didn't I mention the green ground is a SAFETY GROUND and use as a different path to ground in case one of the hots shorts out. Not once did I say the green wire was to be used as the AC return. they are NOT interchangeable GREEN is SAFETY GROUND.... WHITE is and always will be AC return.
The confusion may have accrued when I said that white and green they are at the same potential (() volts)... by the way they are. So There... Dawner

Dawner said:
Industry standard 110 volt AC power
White is AC return also should be electrically at the same potential as the green ground (but different path) also can be tied in to the secondary circuit as AC return
black hot example... used for a sealing FAN LIGHT
red secondary hot example... used for a sealing FAN
green (safety ground) should be hooked to copper rod by circuit breaker box ..and electrically connected to outside of equipment motor housing in case one of the hot short out (this should blow the breaker)... if your lucky

Looking at a plug in the wall LARGE blade is the white wire , SMALL blade is the hot , and BOTTOM MIDDLE round is the green safety ground.

Note: All bets are off.. if not wired by a certified electrician originally and be very careful

Hopefully, I make this clear as mud BUT... If you don't believe me look it up on the internet
PS: I don't really know how electricity works .. I Just know it calms me.

Dawner
Click to expand...
 
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