Wow, you guys really know your stuff. Thanks for all the great replies but now I'm really a bit confused because all I know is Siemens and that's all I've needed to know to run my equipment. I don't know anything about Lonworks or Tridium or ........ I work at one of several colleges within a "district" of colleges. The head of all the facilities of all of the schools has decided that all of the schools must have a central plant with glycol chillers making ice at night and boilers will be centralized also. So with cooling towers, pumps, 500 ton centrifugals, control valves, etc. there will be a lot of critical equipment and the head guy has decided that my school is showing favoritism by adding more Siemens to our campus and therefore he is insisting that we go with Lonworks. He usually gets what he wants but my boss will be meeting with him soon and we have a chance to make a last pitch to "keep it Siemens". I'm pretty sure the head of facilities will get his way and it be Lonworks indeed. With Siemens I'm only worried about pricing after warranty although another problem with Siemens I recently found out is a lot of their guys aren't experienced enough.
So bottom line is I'll be getting Lonworks to control the central plant but I already have Siemens embedded all over my campus. I then won't have much control of what gets installed because they write "or it's equivelant" into the specs. Can anyone explain to me in simple terms how this might work and what are my are my options if I have say. Will Lonworks be an interface between my existing Siemens and some other BAS system. What does Lonworks do and what control sytems other than Siemens would they (the design engineers) be considering for the central plant. What in you guys opinions would be the best set up for my situation?