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electric shock of acrylic light box
I was working on a acrylic light box yesterday which is suspended from the ceiling
on steel cables, the electrics is all mounted on to an aluminium lid which has a metal edged frame which the acrylic box is srewed to.To service the unit the screws are removed from the top edge and the complete acrylic 5 sided box drops down to revel the 6 flouresent tubes and top gear tray/lid.
While working on some steps I received a few shocks from the unit and I’m wondering if they are more due to static from the acrylic panels or if as I suspect, the earth to the gear tray is not very good and there is some residual current leakage going to the gear tray and frame.
If anyone has any previous experiance of possible static shocks from a suspeneded acylic unit, I’d be intrested to hear your comments, other wise I think I need to run a new earth to the gear tray.
Any comments or advise would be welcome
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10 Replies
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I’d run a new earth…. and don’t let H&S know about it or you’ll regret it for a long time 🙂
I get static shocks all the time, but never really had an issue with suspended lighboxes.
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Hi
if the earth is bad on a gear tray you will feel a tingle from all metal components, sort the earth problem & mark on your invoice or instruct that the unit is not to be used until the problem is rectified. If someone gets hurt from it they’ll come looking for someone else to blame.Kev
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You mean you worked on it without isolating it first?
If you still get shocks after isolating the sign then it’s most likely static, but I’d have thought that the earth would have removed any static build up.
Also if your not qualified then you shouldn’t do any electrical work on the sign at all, if you are then you’ll be aware of the dangers so I’ll shut up 😳
Steve
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If you are getting a shock from the box, then there is a problem. The ballast gear inside should be sealed. The earth to the box should in theory provide a lower resistance than your fingers to conduct fault voltages away. Either there is a bad earth in the building or the earth is energised due to the high quantity of "standby" equipment!!!!
This may indicate a problem with the building wiring and not just the box. Get a qualified electrician in and get them to test the electrics. The light box will either be plugged into a std 13A socket or will be wired into a fused spur. Either way it is subject to PAT inspection and that would throw up any problems with the box.
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I do not work with electric signs whatsoever.
But my brother works for an electric company which services signs.
Once when working inside a big sign cabinet (an older one he’d never serviced before) my brother was shocked so badly that he literally saw his entire life flash before his eyes. He was holding a fluorescent tube at the time and was unable to let it go due to the current. He somehow managed to use a tool he was holding in his other hand to smash the tube and then he was OK.
Scary stuff!
Love….Jill -
What you need to do is avoid contact with the ground. Example as the link below 😀
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If not fully qualified dont touch it call in the electrician for you and others safety. It’s the only way to be safe and the within the law.
Paul 🙂
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quote Steve Morgan:What you need to do is avoid contact with the ground. Example as the link below 😀
:lol1: :lol1: :lol1:
I watched a documentary on this a while back, and they said the most dangerous thing they do is power wash the live lines round the insulator stacks……….
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Thanks everyone for your comments.
When we did our initial inspection of the suspended light box, it was not possible to isolate the power without turning off 1/2 the lights in the department store where we were working, and even if we did, they use the bulbs that need a long re-start period, so that wasn’t a practical option for us.
We returned to complete the job this morning, before the shop was open, and with the power isolated and completely disconnected from the sign, we were still getting shocks off of the metal parts of the acrylic sign box. We checked out the existing earth and added a new earth at the point of power entry, then directly into the steel frame to ensure a good earth.
Even after doing this we still got a shock, so my conclusion is that because the box is 5 sides acrylic with a metal lid, all suspended from the ceiling on steel cables, that the shocks must be from static electricity and not from the main power supply.
I know there’s been comments on this post that only a qualified electrician should be working on this unit, but originally we were asked just to replace tubes in a sign light box and surely as we are all sign-makers/installers offering a service to our customers, are we now legally obligated to turn down what should be a straightforward job?
Surely changing a fluorescent tube is no different to changing a light bulb, except the tubes are within a sign box rather than hanging from the ceiling. Do we all now have to become qualified electricians to carry out our trade?
And if an electrician goes to look at the sign, what will they be able to do about static electricity? Is this still a hazard?
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If nothing else get yourself a small multimeter (£20+ ish) and check the next time and Id also advise going on a PAT course. No need to be an electrician, and could be another revenue stream for you. The course is between £80 and £150 depending if you just want the basic ticket or the full blown City and Guilds. If your not 100% on mains, this will give you a good insight to conecting to an existing fused spur and basic testing principles. See your local college.
Ive done the PAT course and am about to embark on domestic installation, 17th edition and then Inspection and Testing of systems. Will be fully qualified by the end of the summer and more than happy to help with future electrical queries.
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