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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Lighting Forum => Topic started by: jasonfinnigan on June 25, 2014, 11:25:57 PM
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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.
(http://i.imgur.com/JiAmnQ8.jpg)
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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.
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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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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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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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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
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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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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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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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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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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.
To really know what's happening, I suggest you power it up and measure voltage potential between the Par chassis and ground. Now, don't get excited if you measure 60 volts, 'cause your iPhone plugged into a non-grounded wall-wart charger will measure half the line voltage normally, but at very low amperage. Then using a pair of alligator clips, insert a 10,000 ohm / 1/2 watt resistor between the chassis and the EGC (Earth Ground Connection). If it doesn't drag the chassis voltage close to zero (within a few volts) then it's definitely leaking too much current. However, if the voltage stays up around 120 volts or so, then they have a serious problem with possible deathtrap scenarios stated above. And yes, one light going leaky could energize the entire lighting truss if it's not properly bonded via an EGC or at least connected to building steel. Lighting techs are even more in danger from a small electric shock since you're often climbing around on ladders or on a catwalk to adjust these lights. It only takes a little shock to startle you and send you on a headlong dive to the floor. I'm going on record as recommending "grounding" these fixture chassis to the incoming power EGC wire. It would only take one leaky transformer in a bunch of lights to ruin your whole day.
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I don't think I would hesitate to ground this. If you clamp it onto a grounded truss it will have its casing connected to ground anyway so I can't see any reason not to connect it internally.
Steve.
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Code says "any metallic parts that are likely to become energized must be grounded."
There must be a ton of fine print to deal with when we get into the no man's land between the NEC and the UL codes.
But as to the Class II appliances, I found this, but it's written in British.
Double insulated or class 2 electrical appliances are products that have been designed in a way so as not to require a safety connection to electrical earth (These products must NOT have a safety connection to Earth).
http://www.double-insulated.com/
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but it's written in British.
We call it English!!
Steve.
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Does cord have a 3 prong edison on it? Just curious-because if double insulated and manufacturing cost is the issue, surely a 2 wire cord with 2 wire plug would be a fraction cheaper?
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Another thought... I would find it hard to believe that UL would list a product with a grounded plug but no actual ground connection internally. Even if the item is double-insulated so the ground is not needed, installing a cordset with a grounding prong and conductor without terminating that conductor internally means that the cordset is not being implemented as intended and is therefore probably in some violation of UL's requirements.
UL's website has a form: "If you would like to report a safety-related concern with a product bearing a UL Mark or an advertising concern, please complete and submit the form below."
http://www.ul.com/global/eng/pages/offerings/perspectives/consumer/fieldreport1/
Maybe you should report it.
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Of course, if it is not listed, probably not much UL can do about it?
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It's not UL Listed nor is it on the MF listing.
Yes, it is a three prong cord. This is what the company said when I said something about the danger of it.
"Dear friend,
Sorry to bother you, and kindly tell you that I had consult our technician for this issue, and according to his reply that if the the unit grounding is disconnected it will not affect the normal using, so please do not worry."
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Even if the unit has a UL sticker, I can by those by the sheet on alibaba....
Sent from my iPhone using Tapatalk
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"Dear friend,
Sorry to bother you, and kindly tell you that I had consult our technician for this issue, and according to his reply that if the the unit grounding is disconnected it will not affect the normal using, so please do not worry."
So is this language British or English or BS? ;D
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Well, they are correct-as long as everything is normal it will be fine. Just like the receptacle I took apart yesterday. Outside, located above a concrete slab with a portable pool about 10 feet away, used to power pool filter and routinely unplugged/plugged while the owner was wet. Non-GFCI, grounds in romex were cut off instead of connected-but so far nothing bad had happened. Of course, it did not get put back together that way!
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Well, they are correct-as long as everything is normal it will be fine.
Yes, but that is not the reason we have codes. Or grounds. etc. If everything was always normal why am I wasting time with having ground rods drove in the ground? This thing will likely never be used because of this. I did check the voltage from ground to the can and it was nothing but still after a little use on it it could be very bad.
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What I find curious about this, is that most people would feel short changed if their new vehicle did not come with a spare tire-even though that spare may never ever be used. Many of the same people see no need to hook up grounds "because they really aren't needed."
Yet, in most cases, if you need a spare tire and don't have one it is merely an inconvenience. However, if you need a ground and don't have one, it may well be fatal.
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What I find curious about this, is that most people would feel short changed if their new vehicle did not come with a spare tire-even though that spare may never ever be used. Many of the same people see no need to hook up grounds "because they really aren't needed."
Yet, in most cases, if you need a spare tire and don't have one it is merely an inconvenience. However, if you need a ground and don't have one, it may well be fatal.
Some folks in other parts of the world have a different value for life safety.
We've been buying lights from China and consider them disposable after 2 years, and we're on a pretty good name basis with "Fong" in Los Angeles that actually takes care of importation. We had the wrong amber LEDs in one shipment, they sent us replacements and we had a local tech swap them, the importer gave us credit on our next order, and they came with the right LEDs.
If you're willing to buy 6 dozen of a model, they can customize certain features, like beam width.
We open every unit and check wiring harnesses and mechanical connections, and tighten all screws. Some units are perfect and others need a fair bit of love. While the importer makes good on things not right, we've found it prudent to order spares/extras at time of original purchase. Nudge, wink.