Ron: ...and 208. 240 three phase is usually high leg delta. Light commercial may not have three phase and thus 240 single phase would be common there.
Dryers are a bad example" See
Wiring a Clothes Dryer and Power Cord - 3-Wire and 4-Wire 240 Volt
The old dryer scheme (single phase 3-wire 240) was L1,L2 and Neutral to the panel. The outer case was permitted to connect to the Neutral at the dryer. It's grandfathered.
The new dryer scheme is (single phase 4-wire 240) or L1, L2, N and G.
An electric water heater would typically be wired with L1, L2 and Ground.
The environmental chamber we had used a dedicated 120 V outlet which has L, N and G. The circulating fan was 120 and the controls were 120. It was a small chamber. Could go from 200 to -80 C.
I can see reasons for keeping the circulator simple by using impeadence protected fans, BUT if you changed to a 3 phase brushless motor, you can easly detect a fan failure before the internal hi temp fuse melts. I failed to make the correct diagnosis and we ended up "Upgrading" the controller because of what looked like a short. The temperature limiter was installed wrong by a student and when it failed it shorted against the case.
With a 3 phase brushless motor for the circulator, you could detect failures before they did damage and use this as a selling point. I had the circulator not work because we were not PMing the oiler cups. My latest boss had a non-prevention or PM mentality and he micro managed to the point you couldn't even do it.
I remember one incident where two people worked more than 8 hours each over the weekend trying to solve a problem with sparking. I came in Monday morning and made a few tests and within 5 minutes, I had diagnosed an outlet with a bad ground. He failed to understand that using the right resources could save money.
He also would not let me repair the water interlock on a 30 KIlloGaus electromagnet because we "don't use it enough" and someone is always there.