I've heard the term used in both instances...both plugging an
instrument into a hot
circuit, and switching circuits to dimmers.
Our old
system that is now thankfully gone had 15 dimmers and 66 circuits. All patching was done with these sliders on the wall that would assign each
circuit to a
dimmer or
non-dim (each
circuit had its own slider). For load testing we would patch the group of circuits into
non-dim 5, which was the 60A
non-dim relay that had an
ammeter in
line. Normally we would just patch them hot right into the
non-dim since the
meter was at the patch board and not up at the
console where the
non-dim switch was. Normally this isn't a good idea since the contacts in the sliders could arc and promote carbon buildup which could ultimately result in high resistance, but we did it anyway since we knew we were getting it replaced soon.
Hot patching (plugging or patching an
instrument into a hot
circuit) is generally not a good idea for more than one reason. Lamps don't like to be patched like that, the resistance of the
filament is different at room temperature than it is at 3000 degrees. Ship can elaborate on the actual figures, because I don't know them. This results in a
current surge at the instant the lamp gets that full 120V, which can lead to the breakage of the
filament. Ever notice how most of the time when the light bulbs in your
house go out, they go out the instant you turn on the
switch? This is exactly why. You might have gotten more hours out of that light
bulb if it were on a
dimmer. The second reason is what I was talking about in the previous paragraph. Hot patching, either with patch cables, sliders, or just plugs on the instruments isn't a good idea because of the arcing that leads to deterioration of contacts.