REVERSING A TRANSFORMER - CAN A NEUTRAL BE USED?

[klassicjam]

Hello. Can a neutral be used in a standard Step Down Transformer converted to a Step Up Transformer? We connected 120VAC (Hot & Neutral) to the Input Side (reversed) and wired the Output Side to the 220 Taps (2 legs) to equal 220 Volts at the Panel connections. The problem that we have is Unbalanced when you measure voltages to ground. We have 148VAC to one leg and 69VAC to the other leg measured to ground with the meter. We don't think this is correct. It seems the current would shift to the lower voltage leg if the panel is loaded. I appreciate your opinion with this connection.?

 

[augie47]

If your 220v side does not have a center tap, you have no reference point to
obtain 120v on that side,

 

[templdl]

Hello. Can a neutral be used in a standard Step Down Transformer converted to a Step Up Transformer? We connected 120VAC (Hot & Neutral) to the Input Side (reversed) and wired the Output Side to the 220 Taps (2 legs) to equal 220 Volts at the Panel connections. The problem that we have is Unbalanced when you measure voltages to ground. We have 148VAC to one leg and 69VAC to the other leg measured to ground with the meter. We don't think this is correct. It seems the current would shift to the lower voltage leg if the panel is loaded. I appreciate your opinion with this connection.?

What is the actual nameplate of the transformer, HV side and LV side, as well as any HV taps? What is the kva of the trasformer? What are the HV vconnections such as H1 and H2 and the LV connections that begin with 'X'? If you can post a picture of the NP that would be helpful as it would eliminate any misinterpretation of a verbal description. I may assume that your intent is you use a single phase transformer to step up from 120 to 240v.

 

[kwired]

When you say you "measured voltages to ground" did you ground the center tap? Or any secondary point for that matter? And if not what two points are you measuring between?

 

[iwire]

The problem that we have is Unbalanced when you measure voltages to ground. We have 148VAC to one leg and 69VAC to the other leg measured to ground with the meter.

You have not bonded the the output of the transformer to ground so it has no reference to ground.

It seems the current would shift to the lower voltage leg if the panel is loaded.

The load is going to see 220 volts line to line regardless of the voltage to ground.

Now the real question is should this system be run grounded or ungrounded.

 

[tom baker]

Per the 2014 NEC, a transformer can not be reversed unless the voltages are shown on the nameplate

 

[kwired]

Per the 2014 NEC, a transformer can not be reversed unless the voltages are shown on the nameplate

I think it says something to the effect that you can't reverse feed the transformer unless it is marked as suitable to be reverse fed. Otherwise I certainly hope it is marked with both primary and secondary voltage whether identified for reverse feed or not. I certainly don't want to be guessing what voltage ratings are