Members fantasticsound Posted November 28, 2006 Members Share Posted November 28, 2006 Currently (pun intended) we have no electrician on staff in our scenic shop. A marquee we built years ago has been uncooperative lately. I believe there was an issue on a rental gig and someone attempted to fix the issue. Poorly, I must say. The construction is: 4 independent circuits wired as floating ground. One each black, red, blue and brown wires respectively for each circuit's hot and individual white neutral conductors. Each pair is pinched by lamp sockets. All sockets are mounted on edge mounted, parallel socket holders. I don't think these sockets were intended to removable after installation, so I doubt the wires have been altered since construction anywhere other than at the plug/receptacle ends. (This is actually three units with three prong edison connectors with positive and neutral alone wired. It's the middle unit that appears to have the issue, although it affects the third unit in some configurations. More on that in a moment.) To summarize, it's 4 independent circuits with lamp sockets wired in parallel to allow for simple chases. The issues are: Circuits 2 & 3 seem to be interacting in the middle panel though we can find no obvious breaks. When powering circuit 2 or circuit 3 alone the lamps on both 2 & 3 light, but at very low output. We measured 60vac on a socket. Powering all circuits simultaneously they all work. What's more, when 2 & 3 are daisy chained to the third panel, the lamps for the circuit being powered (on 2 or 3 only) on the last panel shine bright while the other circuit's lamps barely burn. Measurement on these low level lamp sockets was around 40vac. None of this affects panel one and it stays constant with panel one in or out of the circuits. It appears there is some kind of interaction between circuits 2 & 3 in the middle panel. I imagine it must be causing cancellation from a polarity reversal somewhere, but we've checked and double checked all the plug/receptacle connections and they appear to be the same polarity on every plug/receptacle. Given the simplicity of the circuit I thought I should be able to make some sense of this but I'm entirely miffed. Having enough knowledge to be dangerous I'm ready to throw this to the big boys. Any thoughts? Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 28, 2006 Members Share Posted November 28, 2006 Look for an open neutral wire (should be white but in a DIY situation who knows!) where the source is returning through the load of the other circuit. Link to comment Share on other sites More sharing options...
Members fantasticsound Posted November 28, 2006 Author Members Share Posted November 28, 2006 Okay, pretend I'm 4 years old and explain that again. If there is an open neutral, how is it criss-crossing with another circuit? In theory they should be completely separate, right? Link to comment Share on other sites More sharing options...
Members fantasticsound Posted November 28, 2006 Author Members Share Posted November 28, 2006 Originally posted by agedhorse Look for an open neutral wire (should be white but in a DIY situation who knows!) where the source is returning through the load of the other circuit. BTW - We can see the entire length of each wire (the socket holders are open and a single conductor runs from plug, through the socket holder on one side, across the other side, through the socket holder and out to a receptacle. At every point save for the pass through the cables are clearly visible. They were checked with a continuty tester but I don't know if my buddy attempted to cross conductors and find continuity where there should be none. Link to comment Share on other sites More sharing options...
Members where02190 Posted November 28, 2006 Members Share Posted November 28, 2006 Unless you favor large jolts of electricity and dangerous situations for yourself and the venue, I highly suggest you call a licensed electrician. Link to comment Share on other sites More sharing options...
Members Prog Posted November 28, 2006 Members Share Posted November 28, 2006 I don't understand. Is it (supposed to be) 4 circuits in parallel, each with an on/off switch? Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 28, 2006 Members Share Posted November 28, 2006 The neutrals are usually tied together and then commoned to the source neutral. If the common neutral remains and the connection to the source neutral is lost, it becomes a series connection between the source, through the load 1 through the neutral common, through load 2 back to the source. If there's any difference in the source voltage (either different phase leg sources, different levels, solid state controller backfeed, chase pattern dwell, all can result in current flow therough the series connection and both circuits lighting. I agree with Where... get somebody who is experienced and knows what they are doing as you can get hurt pretty easliy troubleshooting a cross-connection. Link to comment Share on other sites More sharing options...
Members Ear Abuser Posted November 28, 2006 Members Share Posted November 28, 2006 The circuits share the nuetral wire, but when the neutral wire is broken, the current flows through another bulb to get to nuetral. this puts the two bulbs in series. The 120 volts divides up across the two bulbs in series so each one see 60 volts instaed of 120.I wish I had a white board ,a picture is worth a thousand words..... Check each lamp holder for continuity to the nuetral wire, with all the bulbs unscrewed to eliminate any "sneak" circuits. Link to comment Share on other sites More sharing options...
Members fantasticsound Posted November 28, 2006 Author Members Share Posted November 28, 2006 Ok... I was unclear. These are separate circuits that, when used with a small light distro, can be chases by virtue of each circuit only being wired to every 4th bulb on a mount similar to a makeup mirror's lighting. It's a marquee sign. Anyway, it turns out my not-quite-thorough co-worker didn't properly check continuity. There was still a set of mixed up wires and the sign is functioning properly. I'd still like them to have a qualified tech go over it before it's sent out again, just to be certain it's fixed. Link to comment Share on other sites More sharing options...
Members dboomer Posted November 29, 2006 Members Share Posted November 29, 2006 Originally posted by fantasticsound Ok... I was unclear. That's why anybody with any sense would refrain from offering any help here. It's not that we don't wanna help ... but if you've told us something wrong it could be a disaster. Best to have someone qualified come and take a look. Link to comment Share on other sites More sharing options...
Members sharnrock Posted November 29, 2006 Members Share Posted November 29, 2006 Originally posted by dboomer Best to have someone qualified come and take a look. agreed. Link to comment Share on other sites More sharing options...
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