Temporarily hook it up to 120V. Turn it on and see how it works, in terms of giving off heat. If it is meant for 240V, the heat output will be 1/4 of its normal output, so it should be a 240V hookup. Don't try it on 240V first, because if it is a 120V unit, running it on 240V will cause it to put put 4 times correct output and will fry it in a few seconds.