Shocked by pin-patch pin

[derekleffew]

I was trying to determine why two lights on two Par-Bars that were two-fered would not come on, but I thought they had both been on previously. Inside the patch bay of the touring dimmer rack, I pulled the pin to move the circuit to a different dimmer, and decided to feel it to see if it was warm indicating that it had been on recently. With my bare arm on the door of the rack, I touched the pin with the same hand, and got a 120V shock from elbow to finger!

I said some bad words (most directed at myself), then patched the circuit into a different dimmer and ran that one up. Still no lights, so I checked the lamps and both were blown. I replaced both lamps, but the fixtures still didn't work. So I two-fered the fixtures with others.

As to What Went Wrong?, well, that is the question. Obviously I erred in not following the "keep one hand in your pocket" rule. But did the shock I received destroy the lamps? As it's supposed to be supplied by the female outlet, not the pin, where did the current come from?

It might be worth noting that another circuit on the same multi-cable didn't work either, but those lamps were good. And there were two other fixtures on different circuits with bad lamps. Out of 12 fixtures, six not lighting due to 2 bad circuits and 4 blown lamps. Not that it matters, but the fixtures were trimmed at 30', accessible only with a scissor lift, and 400' away from the dimmer rack.

 

[headcrab]

Could the lights have been connected across phases somehow, thus sending 208V along the multi-cable? Then when you pulled the pin from the patch bay the female would still be live. I can't think of a way that a 120V source would burn out lamps rated at 120V. Now, if it actually was 208V...
Besides, you said the lamps would not come on, before you zapped yourself.

 

[mc5w]

You could also have an open neutral in the dimmer unit or the feeder cable. Try connecting a 240 volts baseboard electric heater temporarily to to light cord and see what kind of voltage you get. Might need to do this 2 times with 2 different phases to get an intelligible result.

A more pernicious problemis that one time International Exposition Center in Cleveland, Ohio accidentally hired the colorblind ( YIKES! ) electrician who is running around Cleveland. Check everyting, even those things that cannot possibly go wrong.

Mike Cole

 

[derekleffew]

Could the lights have been connected across phases somehow, thus sending 208V along the multi-cable? ...

You might be onto something. I'm pretty sure the dimmers in question were 31-36, so circuits 1-2 were on ØA, and 3-6 were on ØB (it was a default, 1-to-1 pin patch).

 

[gcpsoundlight]

I heard a really scary storey a while ago. Carey Grammar (A high-end private school down under) comissioned a new performing arts complex, including a new theatre. The person I heard this from worked for a contracted audio company, and was completing the audio set up and tune when the venue manager asked if he could quickly patch some lights for him, as they were running behind. So my freinds assistant jumps up to the dimmer rack, graps a patch and was blown against the back wall. This is the MALE end of a patch, theoreticly not connected to anything AT ALL!. So once the poor chap was taken to hospital, my freind got out his trusty multimeter and checked the patch. Nothing between active and neutral. Nothing between active and earth. 415V BETWEEN NEUTRAL AND EARTH!!!!!!! and it was the same on the other 100 or someting patches! It turned out that they are all wired across phases 1 and 3. They still cant work out how it happened, but the only reason that this guy is still alive is becuase the patch lead melted!