I was asked the question what the difference between an "Open Delta Sevice and a Yankee or Y Service" was. I've looked in the code book and asked more than 5 electrician's and haven't gotten a definite answer. I was wondering if anybody out there could help me. I live in South Carolina, don't know if that makes a differance.

Wye is where the 3 phases are referenced to a central grounded point, looks like a "Y". That is your normal 208.

Open delta, delta "Vee" etc is a delta that skips one of the transformers. Imagine a triangle where you erased one of the sides. That is typically 240v and they centertap one of the secondaries for the ground.
The voltages will be 120/120/208 to ground and 240 between phases.
Open delta is a cheap way to serve a place that needs 3 phase and also 120v since it only takes 2 transformers.
Balancing the phases can be tricky but if done well it works.

Ckeck out the Technical Reference section of this site for schematics of different services.

Dave