Cam lock power hummm / buzz....

Shane Presley

Shane Presley

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Jan 12, 2011
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Ottawa, Ontario, Canada
www.bssproductions.com
I have a community center ( converted old chruch) - that I have been struggling over the past year to get their lighting dimmers situation solid. I had 4 x leprechon LD2400 in there, and there is 4 bars of 6 1K pars, and 2 bars with 12 lekos (6 per side) on it. I replaced the leprechons with 2 x CD80 packs, re-built etc.... I THOUGHT everything would be fine, until the co-ordinator for the space texts me , and says there's a loud buzz near where the camlocks connect. the cams were put in by a contractor, nice grey box, lockable etc... anyway it's located at the back of the stage. The church is being used by an orchestra for rehearsal performance space, and the conductor will "lose his shit" if he hears this buzz... (He makes the centre turn the ceiling fans off - installed 55' up). So any ideas how the CD80's are "buzzier" than the leprechons, or how I might go about masking this power draw buzz?

BTW - the dimmers are located in the basement, not in the same room as the stage...
I am coming off the cams at 200 amps, (down through the floor) to a junction box to 2 x 100 ( knife switch disconnects), then BX to the cd80's....

This is the picture in the basement - from here, the cams run up through the ceiling and tie into the building cam box ( a more rectangluar, off the shelf box) located directly above this set-up...
 

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Re: Cam lock power hummm / buzz....

If its a refurbished CD80 Its probably a 2.4k, As Silas has said, the only way to get rid of the buzz is get rid of the load on the service connect. Your likely getting more "buzz" because the CD80 tends to run a bit higher as far as amperage is concerned than the leprechon. Is there no panel that can get service in the basement for the rack?
 
Re: Cam lock power hummm / buzz....

Seems to me that you need to figure out exactly where the buzz is coming from. If from a panel enclosure, you might be able to "fix" it with a little electrician's putty strategically placed to dampen the vibration. If it's inside one or more of the dimmer packs, you could remove the cover, turn the lights on, and poke around with an insulated stick and see if you can find the vibrating component. There may be loose screws holding a board down. If it's a transformer buzzing, there's not much you can do - any attempt to mechanically dampen the windings with hot glue or epoxy could hinder thermal conductivity.
 
Re: Cam lock power hummm / buzz....

Thanks Guys, I did and on-site, and it's basically when she has the dimmers at 50%, that there is a SLIGHT buzz. The problem is her orch conductor client... he MAY cause a fuss etc...
I mentioned she might be able to build some sort of cover over top of the cams that is insualted, to mask some of the sound. There's nothing I can do electrcially, as everyone has mentioned, other that maybe opening up installed the cam box (which I would rather not do, especically when it's under load) to "feel around" for a vibrating component. It definitely vibrates at 50% load, but goes away in the last 3% before 100% on the master. Thanks for the ideas. TJ, could something in the dimmer be transferring that buzz up 50ft of 2 ott cams to that connection, causing it to vibrate?. it is the 60hz buzz, I'm just wondering where to start to isolate , and look for it. the dimmer packs are buzzing , but they are in the basement. the cam connection upstairs is making the same noise as the dimmer packs...just at about 50% of the volume.
again, it all goes away at 100% master full on , or off.... Also it seemed more predominant in the dimmer handling 4 bars of lights as opposed to two.... and yes they are 2.4 x 12 ch. wired single phase, and jumpered and switched properly.
 
Re: Cam lock power hummm / buzz....

Shane Presley said:
Jordan - Nope, they put a special 200 amp disconnect, with conduit to the cams panel. Cost them a pretty penny ( 25K , just to get the building power turned off), being right down town, I guess it was a big deal....
Click to expand...
25K to pull some meters...
Dang, how do I get into that business?
 
Re: Cam lock power hummm / buzz....

Well you could attempt to just use a styrofoam cover to encase the panel, we just did that on a corporate event since our disconnects took quite a bit of power (created noise) and the client wanted the room to be able to go dead silent.
 
Re: Cam lock power hummm / buzz....

Shane Presley said:
It definitely vibrates at 50% load, but goes away in the last 3% before 100% on the master. Thanks for the ideas. TJ, could something in the dimmer be transferring that buzz up 50ft of 2 ott cams to that connection, causing it to vibrate?. it is the 60hz buzz, I'm just wondering where to start to isolate , and look for it. the dimmer packs are buzzing , but they are in the basement. the cam connection upstairs is making the same noise as the dimmer packs...just at about 50% of the volume.
again, it all goes away at 100% master full on , or off.... Also it seemed more predominant in the dimmer handling 4 bars of lights as opposed to two.... and yes they are 2.4 x 12 ch. wired single phase, and jumpered and switched properly.
Click to expand...
If it buzzes less at full load than an intermediate load, something more complicated than just buss induction is going on, so yes the dimmers are contributing to this. I'm not sure if there's any easy or economical way to fix this (if it's even a problem).

Some kind of external muffler may be your best solution, but I would be very careful how you implement that. Putting something flamable over electrical distribution equipment isn't going to be looked at kindly by the fire marshall. There are also access rules that apply to what can be in the way of the equipment. You're in Canada, so I won't presume to know all the ins and outs of this. In the US you have to have at least 36" of clearance in front of panels, disconnects, etc. That could take the form of a shallow closet made of fire resistant materials (drywall, commercial door, etc.), or there may be some kind of metal enclosure that could be put over the existing equipment. The US NEC describes many of these things in article 110. http://www.nfpa.org/assets/files/PDF/ROP/70-A2010-ROPDraft.pdf
 
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