Insufficient earh bonding - iSolution lighting fixtures.

[daba1955]

During the restoration of some iSolution iMove 250s moving head fixtures, I noticed that the outer casing top/side panels are not properly bonded to earth/ground, which raises a safety issue.

These outer casings are powder-coated, and are each held in place by 4 painted screws. Absolutely nowhere has any provision been made for ensuring these panels are effectively grounded.   I have no idea how they got any form of certification for them .....

On the ones I have repaired/restored, I used a dremel to expose bare metal on the faces where the panels meet up with the chassis (which is bonded to ground), the underside fixings have had their powder-coating removed, the screws have had their shoulders bared, and they were put back with serrated washers.  At least we have metal-to-metal contact.  Hardly ideal, but much better than stock !!

A thorough tear-down might reveal other areas of concern about proper grounding, especially since all the internal screws are painted.  I fear the ideal arrangement will involve a lot of earth-bonding cables !!!

[sandall]

A problem I constantly met with PAT testing new "China Export" marked sound & lighting gear.

[paulears]

Oddly - the 'China Export' explanation of a convenient get around of CE marks is actually untrue. My Chinese factory contents were mystified when I asked a question about China Export marking? The CE marks on many imported goods are simply a copy of the real CE mark - but often with imperfect font reproductions. We sort of created an alternate explanation. The CE marks applied to many products are simply what customers ask for. As in "Is it CE marked?"- which generates a question. "Do you want it to be CE marked?" We say yes, and all they do is screen print it on. 

It's particularly relevant to LED lighting. Most is made (as I've explained before) in very large breeder unit factories. The building is full of small businesses. One does injection moulding, another produces circuit boards. Another does optics. Others specialise in servos, control systems and programming. Power supplies come from another, and there are even businesses who do packaging who pass the boxes on to those who specialise in dispatch and shipping. The upshot is that somebody sits in an office and has an idea for a new light. I'll use an example of mine. A moving head fixture with 7 bee eye style rotating lenses. Capable of near parallel beam or a wide wash. RGBW and a zoom feature. They source every part from within the facility and sell them to people like me. Buy ten, need eight - but get tempted to use the two spares. The product has a CE mark, and a nice certificate. There is no way to get a CE mark for a product run of at the most, a few hundred. The CE mark is for something similar, but not the same thing at all. In my case, 7 LED modules was too much for the drivers and lots have now died. I thought I'd order another 10 and take a chance again - they've lasted three years. No - the thing has been scrapped. Probably too many failures, I don't know. The new version has 6 LED modules, not 7, but is the same housing and parts, but with the centre lens missing. No doubt the new version will also have a CE mark, because we ask for it!

Remember that we ask, they try to supply, and often have no clue about the product or what we actually want. 

I asked a supplier I have used many times if they had some microphones for two-way radios. The pictures they sent were of an Icom branded product. I asked them if they could do the same for Kenwood? They responded asking if I wanted "For Kenwood" - so I said yes. This is what arrived. If I had said I need CE marking, the same thing would happen. The China Export explanation is something we have invented. They just do what we ask for - the idea it signifies anything is an illusion. 

 

[sandall]

Indeed Paul. In this case it was just a flippant way of saying "Made in China", as virtually everything I tested had been. Mind you, the OP's problem isn't limited to imports; you can spend a lot of time with various forms of abrasion to get a decent continuity reading on most UK generics (especially CCT).

Edited May 2, 2023 by sandall

[KevinE]

Modern prolight (isolution) stuff certainly have their panels bonded either by bare parts under the screws or by seperate earth cables. But I wouldn't be too concerned, I've seen it on many things with powder coated steel casings, amplifiers, lights, what-have-you. Maybe those lights originally had a star-washers under one screws that could bite through the paint, and they got lost, unless you're the first to dismantle them.  If the part in question is not designed to be routinely handled while in use, I doubt it presents much risk in reality, no matter what the relevent standards may require.

 

[daba1955]

On 5/2/2023 at 10:54 PM, KevinE said:

Modern prolight (isolution) stuff certainly have their panels bonded either by bare parts under the screws or by seperate earth cables. But I wouldn't be too concerned, I've seen it on many things with powder coated steel casings, amplifiers, lights, what-have-you. Maybe those lights originally had a star-washers under one screws that could bite through the paint, and they got lost, unless you're the first to dismantle them.  If the part in question is not designed to be routinely handled while in use, I doubt it presents much risk in reality, no matter what the relevent standards may require.

 

In this instance, the fixtures were sold to a gigging DJ, and they'll be rigged and de-rigged with alarming regularity - up to 4 times a week. I didn't feel comfortable not doing anything....

[pmiller056]

Different industries have differing requirements for equipment/appliance safety earthing. What is appropriate in our industry?

A friend spent his early career working with medical electronic systems. As a consequence, every bit of exposed metalwork on anything made by this person is separately wired in green/yellow wire to a very crowded, bulky star point earth bolt close to the power inlet. This is appropriate for medical electronics, but probably not for our industry.

My approach (because of my background) is any bit of metal that carries or fixes a mains 'live' part is wired to the main earth terminal. Any exposed metalwork that does not have mains live parts on or near it, and so cannot be expected to become live under fault conditions, is casually earthed through the fixing screws. In some equipment enclosure designs, fixing screws for metal panels go into plastic, so a wire to the earth terminal should be added in this instance.

Star washers can be used, they are quick and effective, but most get lost during the lifetime of the equipment. On occasion where screening is important such as audio and video equipment, metal panels with no live parts should have an earth connection added.

How equipment will be inspected and tested during its lifetime needs to be considered too. Most people doing PAT testing look for an obvious bolt/screw head to attach the earth test probe to, do the test and move on the the next thing. I've never seen anyone test each external metal panel separately - unless the first test was unsatisfactory and a 'better' test point needs to be found.

What are other people's thoughts on this issue?

[daba1955]

Having worked in industrial automation for over 30 years, I can honestly say I have never seen an enclosure where ALL of the separate panels, doors, cable gland plates etc. were not physically bonded with a decent sized bonding wire back to a central bonding location or strip.

Even if the door only had LV circuits on it, like 12/24V lamps and pushbuttons, displays etc., the door was bonded to earth.

On the lighting fixtures in question, I very much doubt any testing could have been carried out, since all of the visible and available screws were black japanned and would not have been a decent connection to the panel they were screwed into.  The lamp housing in the movable head carries the striking voltage for a mercury vapour lamp, and this removable assembly (enough to change the bulb) was not earthed at all. Earth bonding was provided near the back panel where mains voltage enters the equipment, but the front panel where the pushbutton/display board sits was not bonded, other than through the powder-coated chassis components being screwed together with painted screws - no star washers anywhere.

Just feel that it's a accident waiting to happen....

[KevinE]

There's nothing to stop you adding supplementary bonding as an aftermarket modification if you feel more comfortable doing it, but in the world of 'pro-sumer' lighting equipment, you'll be kept busy! Prolight Concepts (isolution) are a uk company, and probably the largest manufacturer of disco lighting and sound equipment in the country, and they're bound to have put these on the market with the relevent standards. Although I can't see any harm in sanding a little area of panel for reliable metal to metal contact, anything more is likely to be a modification to the design that you will ultimately be responsible for. I suspect your experience in industrial automation has led you to expect higher construction standards than those generally seen in the semi-pro stuff sold for disco use and of course they are priced for and aimed at a different market sector.

 

[daba1955]

40 minutes ago, KevinE said:

There's nothing to stop you adding supplementary bonding as an aftermarket modification if you feel more comfortable doing it, but in the world of 'pro-sumer' lighting equipment, you'll be kept busy! Prolight Concepts (isolution) are a uk company, and probably the largest manufacturer of disco lighting and sound equipment in the country, and they're bound to have put these on the market with the relevent standards. Although I can't see any harm in sanding a little area of panel for reliable metal to metal contact, anything more is likely to be a modification to the design that you will ultimately be responsible for. I suspect your experience in industrial automation has led you to expect higher construction standards than those generally seen in the semi-pro stuff sold for disco use and of course they are priced for and aimed at a different market sector.

 

Pricing and aiming at a target sector should never be a substitute for any safety issues.  I would never undertake any modification to equipment that I felt unnecessary.

Using non-visible, sketchy, and in the worst-case scenario, ineffective grounding methods is a no-no IMHO.

But I hear what you are saying, however I doubt any law-suit would go ahead if I've made a product safer for the user, without compromising its functionality.

Prolight do not make, and have never made these fixtures, they just inherited the name iSolution- nor do they support them, and I'm guessing their current product range meet all safety standards.

Edited May 9, 2023 by daba1955