208VAC is the typical phase-to-phase potential in 3-phase circuits.
I don't know anything about the Challenger, but I'd guess that any internal accessories (fan motor, etc.) will not like the 208.
You can get a step-up transformer that sits on the load side of your service to arrive at 240VAC - call you local electrical supplier and describe your delimma - he'll set you up. You can hard-wire the unit, or leave it portable. I'd advise a hard-wire installation, with the transfomer output feeding a new 240VAC panel that you can run your branch circuits from.
...from the Gadget Garage
MM 210 w/3035, BWE
HH 210 w/DP 3035
Victor O/A "J" series, SuperRange
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