Enclosure safety 1

[Marke]

Hi

Recently I came across some equipment with a plastic enclosure and a "snap on" cover.
This equipement has input and output terminations that are fully exposed when the cover is removed.

The enclosure is designed to be wall mounted and there is no toll required to remove the cover.

The equipment is rated at 400 Volt 50Hz and around 100A. IP40

I am concerned about the potential hazard that this equipment presents. I have always been of the belief that the cover must be held closed in a manner that requires a tool or a key to open it, and this certainly does not fall into that category.

I welcome your comments from both a "moral" and a "legal" perspective.

Best regards

Mark Empson

http://www.lmphotonics.com

 

[buzzp]

Legally, I don't think there is anything to be done if the enclosure meets the designed IP rating. However, since it has an IP rating and not a NEMA or UL, it sounds like it is used in the EU. If this is the case, it may not meet the 'finger' safe requirements. However, the cover may be how they are meeting this requirement. Not sure. I used to know IP ratings but does not one of the numerals designate finger safe?

Morally- I guess I don't know enough about it but if it is only "supposed" to be opened by qualified personnel then I don't see an issue unless its in an area where the public may be. You can't protect idiots from themselves. There should also be some voltage warning signs etc.

 

[jraef]

Marke,
I believe this is in fact a "moral" issue rather than a regulatory one. Both NEMA and IEC enclosure designations speak mainly to protection of the components inside from foreign objects outside. The only thing they say about protection of people outside has to do with the size of object they try to stick in! (OK stop laughing...)

NEMA only refers to "incidental contact" which it defines as "accidental or unintentional". That means that any "fool-with-a-tool" can get in and do damage to their body parts (I said STOP LAUGHING!). The fuzzy part comes up with clips, as you saw, and thumb screws because technically the only tool you now need is a finger and thumb, and maybe even just a finger.

IEC at least, in the various "degrees of protection", gets precise about describing the size of the penetrating object (OK, thats it, if you don't stop that snickering I will QUIT!), such as the back of the hand, a finger, a tool, etc on down to a wire. But still, they also use a vague term "access". They don't even go so far as to require a tool to get in.

Safety regualtions are another matter. Here in the US we used to use a voluntary standard called JIC which combined NEMA issues with industrial safety. The safety issues have now been somewhat adopted by OSHA, the government Occupational Health and Safety Administration. Under the old JIC rules, anything having a potential of over 48VAC (I believe) that requires regular access (there's the catch) must have a permanently attached cover, i.e. hinged. On small boxes however, that can be, and often is, still just a screw cover with a little chain on one corner to hold the lid after you open it. For you, I;m sure trhere is a Kiwi equivalent to OSHA (what government would pass up an opportunity to tell people what to do?). They would likely be the ones to have a problem with ease of access to live components.

What you are forced to do as a minimum and what you must do as a moral imperatve are often the issues that define and separate good engineers from so-so engineers.

"Venditori de oleum-vipera non vigere excordis populi"

 

[dgallagher]

In the US, most fiberglass enclosures like this are available with the lid either screwed down or with quick release latches. They can be changed into either configeration. Generally if it is a box that requires periodic access to the inside, it is preferred to have the quck release latches. Both configerations meet NEMA 4X requirements in plastic or stainless steel. Painted steel boxes are normally NEMA 4.

http://www.reliabilitydirect.com/junctionboxes/junctionbox.index.htm

 

[UKpete]

Marke, my employer is a UK manufacturer of a wide range of starters and motor control centres and I believe they work to IEC specs.

Generally all the 400V equipment is in metal enclosures with hinged doors, they are fitted with isolators and it is not possible to open the door without the isolator being in the off position. Once the door is open, the live input terminals are protected with a finger-proof plastic shield on which there is a "flash" symbol. We've all seen this type of equipment and I am suprised that anyone markets the item you are describing. Even ignoring local standards/codes etc, there may be general health & safety legislation that say an employer would fall foul of, particularly if there was an accident.

Nothing is fool-proof, but at least if you provide levels of protection of live terminals it is an effective warning that danger lurks within (beyond that survival of the fittest kicks in!)

The equipment you describe sounds cheap and nasty.

 

[buzzp]

I don't see any difference between a twist knob that opens a cover vs. a snap-on cover. In either case, the door is quickly opened. If it is really a concern, use a door with a 'lock'. Anything less would not limit the access to the enclosure. It does not matter what fastening mechanism they have, no lock, then no good.
In the US, after the panel is opened it is very common to only have a shield in place, (of which can not be easily removed. This is where the HV terminations take place. Any low voltage wiring is generally not protected inside the panel but it is separated from the HV side, usually by another access door (with no particular fastening mechanism)or flash over shield.
If this panel is in an area with no public access there is no problem. If you really want to protect the enclosure from access then nothing less than a lock will do. I don't care if you use a knob, snap-on cover, screws, or whatever, none of these will do, morally (for a public area). Enclosures that have doors, front covers, with something less than a lock are very common. Based on the limited info I have on your application, I see nothing wrong.
Given the new concerns over flash protection, these types of enclosures may see limited use in the future. For now, they are very common, especially for 600V or less.

 

[mc5w]

Sounds to me like your device is intended to be in another enclosure that keeps unauthorized people OUT. Even when you are an authorized person it does help to fingerproof stuff. The less exposed energized metal there is the less chance of getting your arm wrapped around your head.

If a bus or terminal is not knuckeproof or fingerproof, tape up the f@#%&$g bus!

Mike Cole, mc5w@earthlink.net