Convert split phase power to single phase power

[JPBallon]

I have been tasked with supplying a 240VAC circuit that is wired Line-Neutral-Ground. What I have available is a split phase 120V/240V distribution bus (L1-L2-Neutral with 240V between L1-L2). Since I have never encountered this situation before, my gut feeling tells me that I can connect L1 and L2 of the supply to the inputs on an isolation transformer and ground the one of the output lines to neutral with the load ground connected to the supply ground. Am I barking up the wrong tree?
Thanks ahead of time for all the comments and answers.

 

[Saturn_Europa]

I have been tasked with supplying a 240VAC circuit that is wired Line-Neutral-Ground. What I have available is a split phase 120V/240V distribution bus (L1-L2-Neutral with 240V between L1-L2). Since I have never encountered this situation before, my gut feeling tells me that I can connect L1 and L2 of the supply to the inputs on an isolation transformer and ground the one of the output lines to neutral with the load ground connected to the supply ground. Am I barking up the wrong tree?
Thanks ahead of time for all the comments and answers.

What type of load are you supplying?

 

[winnie]

If you really need 240V L-N then you need some sort of a transformer, as you surmise. I would first confirm that you really need 240V L-N; most North American 240V appliances expect 240V L-L. Most European 240V appliances don't assume a known polarity (meaning that they can take L or N on either supply terminal) and will happily work on North American split phase power.

If you use an isolation transformer, then you will need to follow the rules for grounding/bonding a transformer; one of the output terminals would get 'grounded' and bonded using a GEC, and then all neutral and ground connections would go to the grounded terminal (or bus connected to the grounded terminal)

You could also use an 'autotransformer' where you have two 120V coils. One coil is connected to your 120V L-N supply, the second coil is placed in series with the first to derive 240V L-N. Ground and neutral are direct from your split phase supply, the transformer generates the 240V terminal. This approach uses the supply side bonding, which simplifies your grounding issues, but puts all of the load on a single leg of your split phase system.

The isolation transformer approach makes sense for a large load; the autotransformer makes sense for smaller loads.

-Jon