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Author Topic: Ground on LED Par Can  (Read 6876 times)

jasonfinnigan

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Ground on LED Par Can
« on: June 25, 2014, 11:25:57 pm »

So I bought a Chinese LED Par 64 Can (It's a metal housing), looks good but haven't tested it much yet. But I took it apart cause I wanted to see the inter-workings before I bought more if I was going to. the ground from the Sjoow cable on the inside is not connected anything, it is just cut off. Do you think this is safe being that it goes straight into a AD-DC low voltage (12V) transformer after that?

The electrician in me wants to say that everything needs a ground because a Neutral and a ground is not the same (even if bonded).

Though I want this to work, I also know AC and DC ground is not equal so the ground won't do anything unless it's the actual ac input/cables shorting.

Thoughts?

Edit: btw the one I got is similar to this. but it is a Chinese no name version, and is around $30 on eBay. http://www.musiciansfriend.com/pro-audio/lighting-led-par-64-light/581511000001775

Edit: added Picture. if you zoom in you can kind see where the ground conductor was cut off even with the jacket.
« Last Edit: June 26, 2014, 01:57:33 am by JasonFinnigan »
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Steve M Smith

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Re: Ground on LED Par Can
« Reply #1 on: June 26, 2014, 02:55:36 am »

If it was mine, I would strip back the cable, put a tag on the earth wire and bolt it somewhere suitable.

It looks like the incoming power is being rectified then converted to a usable voltage by a switch mode power supply so there is no transformer isolation there.


Steve.
« Last Edit: June 26, 2014, 02:58:12 am by Steve M Smith »
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Mike Sokol

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Re: Ground on LED Par Can
« Reply #2 on: June 26, 2014, 07:13:22 am »

If it was mine, I would strip back the cable, put a tag on the earth wire and bolt it somewhere suitable.

It looks like the incoming power is being rectified then converted to a usable voltage by a switch mode power supply so there is no transformer isolation there.


Steve.

That switching transformer likely does provide insulation between the line and low voltage sides, and if there's less than 0.75 mA leakage between the line and chassis, then they can cut the EGC (Equipment Grounding Conductor) and still pass UL inspection. However, I doubt that the manufacturer is concerned with UL. My gut feel is to provide a frame ground, but that's something I need to think about a bit more. 
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Ray Aberle

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Re: Ground on LED Par Can
« Reply #3 on: June 26, 2014, 08:20:06 am »

However, I doubt that the manufacturer is concerned with UL. 

Or making sure that every unit that comes off the "line" is made the same. Maybe they passed one, and then "who gives a butt" about the actual every day to day production.

Or it's just not been inspected.

Or someone had a rough day and messed up.
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Steve M Smith

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Re: Ground on LED Par Can
« Reply #4 on: June 26, 2014, 08:34:29 am »

That switching transformer likely does provide insulation between the line and low voltage sides

Yes, but unless the voltage regulation feedback is either optically coupled or non existent, it will connect through to the secondary side.


Steve.
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Kevin Graf

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Re: Ground on LED Par Can
« Reply #5 on: June 26, 2014, 08:51:17 am »

Does the can have a Class II or double insulated electrical appliance safety symbol? The symbol is a square inside a square. If it doesn't have has the symbol then it doesn't need a Safety Ground wire.
(typo corrected)
http://en.wikipedia.org/wiki/Class_II_appliance#Class_II
« Last Edit: June 26, 2014, 04:50:23 pm by Kevin Graf »
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jasonfinnigan

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Re: Ground on LED Par Can
« Reply #6 on: June 26, 2014, 10:02:36 am »

Does the can have a Class II or double insulated electrical appliance safety symbol? The symbol is a square inside a square. If it doesn't have the symbol then it doesn't need a Safety Ground wire.

http://en.wikipedia.org/wiki/Class_II_appliance#Class_II

I think you got that backwards.
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jasonfinnigan

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Re: Ground on LED Par Can
« Reply #7 on: June 26, 2014, 10:09:44 am »

I wouldn't be as concerned if the chassis wasn't metal, but with the chassis metal it concerns me.

IMO right now it's a death trap. if the hot wire was to come out of the terminal block and touch the outside of the can, it will then be energized. It will then shock them if they touch it as they ONLY path to ground. It will also not trip the breaker, I believe.  I know it's a painted metal, but still don't tell me it's non conductive.

If this is in a production, it's even worse, energizing trussing its on.. and possibly even the ground of the DMX XLR, which then in turn could energize the lighting console. and if that or the grounded barrel of the dmx cable touch an audio cable.. etc, You see where I'm going with this.

Call me crazy. Obliviously it takes a lot for something like that to happen, but I tend to be very picky about power - and electrical safety even more so.
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Stephen Swaffer

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Re: Ground on LED Par Can
« Reply #8 on: June 26, 2014, 10:25:33 am »

Code says "any metallic parts that are likely to become energized must be grounded."

You get to decide the definition of likely.

IMO, any lighting truss should be grounded (term is bonded-which means an intentional electrical connection), and frame of light should be grounded as well.
FWI I installed some cooper LED can inserts a few weeks ago.  Same deal-power goes into 12 vdc power supply through an edison lamp holder.  Insert includes a pigtail with instructions to connect it to the can-which is grounded through supply circuit. So, I am guessing if you ask Cooper engineers, tehy would say to ground it.
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Steve Swaffer

Jonathan Johnson

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Re: Ground on LED Par Can
« Reply #9 on: June 26, 2014, 11:03:54 am »

I can't see any harm in grounding. If the manufacturer grounded it, it might raise their cost by seventeen cents, while their margin is thirteen cents.

Profit on items with a lot of competition tends to be heavily weighted to the retail side. There usually isn't much in the manufacturing. That's why there's a race to the bottom in quality.
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Re: Ground on LED Par Can
« Reply #9 on: June 26, 2014, 11:03:54 am »


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