Originally Posted by Lux

That's what we electricians refer to as a "high leg." Gives you 208 or 240 (depending on your feeder transformer's output) to neutral. If you meter between it and a 120v leg, you'll still only get the 208 between legs and can utilize such attachment for 240volt equipment. WARNING -- If said equipment has a neutral, it probably has componentry which utilizes 120v, making attachment to the high leg a very risky proposal.

As a licensed master electrician and electrical contractor, I'd recommend that you adhere strictly to the nameplate rating of the equipment and the NEC when implementing your installation.

If you have any specific questions, ask here or PM me.