Hi folks, glad to have joined here. I have found a great many useful posts here and so I thought I should join up and maybe contribute!
Now, I am not actually involved with installation of any HVAC equipment. I am a DDC/controls/building automation designer and programmer, working for a major electrical contractor. Basically, I get the prints, examine the sequence and specs, and then design and program a control system to the engineer's and customer's specification. It's a hell of a lot of fun for me, and I've learned a lot about the equipment. My company works along with some great mechanical contractors and we've always worked together to keep the customer happy.
Most of my work is in the 200 - 1500 control points range, but I do the occasional retrofit with fewer than 100 points and we also have some jobs that have been four or five thousand points. My favourite work is generally new construction, because I can design exactly as I want without worrying about existing stuff. My least favourite is retrofitting older pneumatic systems to DDC, because it always seems the engineer hasn't done his homework and things get messy.
So, although I am kind of peripheral to the industry, I still feel I can learn a lot from you all and maybe I can offer some help at times too.