Okay, let's break this down. It's important to get the wiring correct to avoid damage or safety hazards.

The correct wiring is: One hot leg to the breaker, and the other hot leg to neutral.

Here's the reasoning: The Purpose of the Transformer

The transformer is stepping up the voltage from 120VAC to 600VAC. It needs a complete 120VAC circuit on the primary (source) side to function properly.

Voltage Between Legs

In a 120/208V system, the voltage between any two hot legs is 208V. The voltage between any hot leg and neutral is 120V. You need to use 120 V from your 120/208 panel, which is a hot leg to neutral.

Functioning Circuit

To get the required 120VAC on the primary (source) side of your step-up transformer, you need to connect one of the hot legs from your 120/208V panel to a breaker in the panel, and the other hot leg to the neutral.

Grounding is Different

Grounding is for safety and fault current path. It's separate from providing the operating voltage for the transformer. There will be a grounding connection, but it is in addition to the voltage connections. The transformer frame should be grounded to the system ground, and potentially the neutral as well, depending on local codes.

Why not ground?

Connecting one leg of the 120V supply to ground instead of neutral would create a short circuit. The neutral is bonded to ground back at the service entrance, so in effect you'd be connecting one hot leg directly to ground. This would trip the breaker immediately.

Important Considerations and Cautions (Even with Limited Internet)



Local Electrical Codes

Always follow your local electrical codes. These codes may have specific requirements for transformers, grounding, and wiring in your area. What applies in the contiguous US might not apply where you are. Contact your local electrical inspector or a qualified electrician before doing any wiring.

Transformer Nameplate

Carefully review the transformer's nameplate information. It should show the required primary (input) voltage, secondary (output) voltage, KVA rating, and any specific wiring instructions. This information is critical.

Overcurrent Protection

Ensure the breaker feeding the transformer on the 120V side is properly sized to protect the transformer. A 5KVA transformer at 120V will draw approximately 41.6 amps (5000 VA / 120V = 41.6 A). You'll need a breaker sized appropriately for that load and the wire gauge you're using.

Grounding

The transformer enclosure MUST be properly grounded. Typically, this is done by connecting a grounding conductor from the transformer's grounding lug back to the panel's grounding bus.*

Qualified Electrician

If you're not a qualified electrician, it's strongly recommended to hire one to do this work. Working with electricity can be dangerous, and incorrect wiring can damage equipment or cause injury.

In summary, connect one hot leg to a breaker and the other hot leg to the neutral bar. Ensure proper grounding of the transformer enclosure, and follow all local electrical codes. If in doubt, consult with a qualified electrician. Flag for review