Grounding a chassis for line voltage safety

[Chris Carlen]

John Larkin wrote:

On Wed, 31 Mar 2004 17:47:05 -0800, Chris Carlen
crcarle@BOGUS.sandia.gov> wrote:
Wowy-dowy! If that is what is involved in UL certification, then this
makes me very curious about what one does who wishes to sell a
commercial instrument (in the US primarily, but interested in gloal as
well) that is line powered but is also a "one-off."

It would appear totally impractical to UL test in this case, and so
mustn't there be some exemption from requiring a cert. to sell the item
legally? Yet, how does one protect themselves from liability (other
than by designing well so that it *is* as safe as possible to begin with)?



UL is not a law-enforcement agency. Some states have laws that require
consumer items to be UL (or equivalent) certified, but seldom address
scientific or industrial items. UL and FCC both have explicit
exemptions for many classes of "test equipment".

In short, there's no enforcement. Even "CE" is said to mean Can't
Enforce.

My company designs everything to conform to UL and CE safety
standards, but we don't formally test or certify. This is good for the
products and good for the health of our customers.

John

Do you find many people care about whether those cute little "UL" and
"CE" insignia are on there?

Of course, since you can't put those on without the actual certs. (and I
know a respectable fellow like yourself wouldn't), how does the customer
know they are getting a well designed product, if they don't have
personal experience with your company?


Funny (or not) story:

Whne I first started at Sandia, I was given a heater controller chassis
by one of the scientists, to straighten it out.

It turns out that they contracted some outside vendor to assemble a
commercial heater controller into a chassis, complete with line in and
heater power out receptacles.

They got the line in correct, using a male chassis mount "wall plug."

But shockingly (pun intended) they installed a MALE plug for the line
power output to the heater!!!

The item wasn't certified, and I have some confidence that it wouldn't
have made it through certification.

I regret not doing more about it other than fixing it, such as giving
them a call and a royal chewing out.




Good day!



--
____________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarle@sandia.gov

 

[John Woodgate]

I read in sci.electronics.design that Chris Carlen
<crcarle@BOGUS.sandia.gov> wrote (in <c4hk2n01onp@news1.newsguy.com&gt
about 'Grounding a chassis for line voltage safety', on Thu, 1 Apr 2004:

Whne I first started at Sandia, I was given a heater controller chassis by one
of the scientists, to straighten it out.

It turns out that they contracted some outside vendor to assemble a commercial
heater controller into a chassis, complete with line in and heater power out
receptacles.

They got the line in correct, using a male chassis mount "wall plug."

But shockingly (pun intended) they installed a MALE plug for the line power
output to the heater!!!

Perfectly normal bad practice 55 years ago. When I was at school (US

'high school' equivalent) we did a physics experiment set with a sodium
lamp (spectrometer, Newton's rings etc.) The experiments were carried
out in a dark room, with the teacher not present. The mains supply was
connected to the lamp ballast with crocodile/alligator clips! After a
potentially fatal accident to one student (one clip in each hand), the
set-up was changed to the 'much safer' arrangement with 240 V mains on
the exposed pins of a connector.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[John Larkin]

On Thu, 01 Apr 2004 09:38:31 -0800, Chris Carlen
<crcarle@BOGUS.sandia.gov> wrote:

John Larkin wrote:
On Wed, 31 Mar 2004 17:47:05 -0800, Chris Carlen
crcarle@BOGUS.sandia.gov> wrote:
Wowy-dowy! If that is what is involved in UL certification, then this
makes me very curious about what one does who wishes to sell a
commercial instrument (in the US primarily, but interested in gloal as
well) that is line powered but is also a "one-off."

It would appear totally impractical to UL test in this case, and so
mustn't there be some exemption from requiring a cert. to sell the item
legally? Yet, how does one protect themselves from liability (other
than by designing well so that it *is* as safe as possible to begin with)?



UL is not a law-enforcement agency. Some states have laws that require
consumer items to be UL (or equivalent) certified, but seldom address
scientific or industrial items. UL and FCC both have explicit
exemptions for many classes of "test equipment".

In short, there's no enforcement. Even "CE" is said to mean Can't
Enforce.

My company designs everything to conform to UL and CE safety
standards, but we don't formally test or certify. This is good for the
products and good for the health of our customers.

John



Do you find many people care about whether those cute little "UL" and
"CE" insignia are on there?

Of course, since you can't put those on without the actual certs. (and I
know a respectable fellow like yourself wouldn't), how does the customer
know they are getting a well designed product, if they don't have
personal experience with your company?

We have done a full CE file for a few products that our OEM customers
wanted CE-marked to they could sell them (in systems) in Europe. We
shared the costs of testing. You can self-certify to CE and slap the
sticker on, but to be fair you really have to contract the EMI testing
to a proper test lab that has all the right gear. It's 'legal' to
self-certify the Low Voltage Directive stuff, as long as you make a
competant study and keep the results on file.

Lots of people apparently *do* slap on CE stickers without benefit of
testing. "The presence of a CE-mark sticker verifies the presence of a
CE-mark sticker."

John

 

[mike]

John Woodgate wrote:

I read in sci.electronics.design that mike <spamme0@juno.com> wrote (in
406AF871.40206@juno.com&gt about 'Grounding a chassis for line voltage
safety', on Wed, 31 Mar 2004:

It's good to seek opinion. But in the end there's only one person's
opinion that matters. The certification agency. And there's probably
more than one. Get the written test criteria from every agency who needs to
approve your product and try to find a solution that makes them
all happy.


Doesn't apply in Europe. No 'certification'.

At the final certification test is NOT the time to find out that the guy
you met on the internet had an obsolete standards document.


Yes, current editions of standards are essential. But some

My point exactly!!! Which "some" of you???

of us already
don't give advice based on old standards. Don't tar everyone with the
same brush.

I waste a lot of time reading newsgroups. I find that virtually ALL
(as in high percentage) internet advice is CRAP. People who haven't a
clue weigh in on the issue. "My brother's x-wife's son's shop teacher
has a cousin who refines Uranium all the time, so I declare it safe!!"
So, Yes, my brush is very broad. The internet is a great place to get
leads to info that you independently verify.

To be fair, this particular newsgroup has a relatively high percentage
of cluefull people. In particular, I find YOUR inputs well thought out
and indicative of relevant experience. But even here, you still
represent the minority.
But many people asking questions have not the ability to sort the good
stuff from the overwhelming majority of downright BAD advice. Sorry if
I accidentally got some on you.

mike

--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[mike]

Chris Carlen wrote:

John Woodgate wrote:

I read in sci.electronics.design that Walter Harley
walterh@cafewalterNOSPAM.com> wrote (in <c4f4rt$k4q$0@216.39.172.65&gt
about 'Grounding a chassis for line voltage safety', on Wed, 31 Mar
2004:

"Chris Carlen" <crcarle@BOGUS.sandia.gov> wrote in message
news:c4f0060eh3@enews2.newsguy.com...

Yes, I should probably get familiar with a specific cert. agency. I
haven't done so yet since nothing we do here ever gets used other than
internally as custom lab instrumentation.


And is probably one-off construction in many cases? I've heard that UL
certification is not only expensive (>$10k), they require several
units to
destructively test. Very impractical for a lab situation, even one with
defense funding, I'd think. Also I'm not sure how long the process
takes.

But that's just hearsay, not knowledge. Perhaps someone with real
information can correct me.



It's substantially true. Certification is inappropriate for such one-off
equipment. What is by NO means inappropriate is *making the equipment
safe according to applicable standards*. And that is important for
health and safety at work purposes, which are really rather important.


Wowy-dowy! If that is what is involved in UL certification, then this
makes me very curious about what one does who wishes to sell a
commercial instrument (in the US primarily, but interested in gloal as
well) that is line powered but is also a "one-off."

It would appear totally impractical to UL test in this case, and so
mustn't there be some exemption from requiring a cert. to sell the item
legally? Yet, how does one protect themselves from liability (other
than by designing well so that it *is* as safe as possible to begin with)?

That's why you see so much stuff powered from a wall-wart. The wall
wart is certified and can take much of the pain out of safety testing
your product. And give the plaintiff a deeper pocket to go after.
"I don't have to outrun the bear. I just have to outrun you!"

There seems to be a dismissal of the requirement for certification of
internal fixtures etc. While this is an economic reality for the company,
I'd hate to be the designer of the fixture that injured
Suzy-production-worker. Especially if she had a good lawyer and I'd
designed the system based on internet advice.

Call me paranoid, cause I am...
mike

You can make equipment 'safe' in this context by attending to design
issues;


Yes.


Thanks for the input.


Good day!

--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[John Woodgate]

I read in sci.electronics.design that mike <spamme0@juno.com> wrote (in
<406C8A00.4080801@juno.com&gt about 'Grounding a chassis for line voltage
safety', on Thu, 1 Apr 2004:

There seems to be a dismissal of the requirement for certification of internal
fixtures etc.

What people have said is that *certification* is impracticable and
unnecessary, but ****safe design and construction**** is practicable and
**essential**.

While this is an economic reality for the company,
I'd hate to be the designer of the fixture that injured Suzy-production-worker.

So would I, and I wouldn't need the possibility of legal action to
motivate that.

Especially if she had a good lawyer and I'd designed the system based on
internet advice.

Once again, you condemn ALL Internet advice indiscriminately. If you
really mean that, why not just go away?
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[mike]

John Woodgate wrote:

I read in sci.electronics.design that mike <spamme0@juno.com> wrote (in
406C8A00.4080801@juno.com&gt about 'Grounding a chassis for line voltage
safety', on Thu, 1 Apr 2004:


There seems to be a dismissal of the requirement for certification of internal
fixtures etc.


What people have said is that *certification* is impracticable and
unnecessary, but ****safe design and construction**** is practicable and
**essential**.


While this is an economic reality for the company,
I'd hate to be the designer of the fixture that injured Suzy-production-worker.


So would I, and I wouldn't need the possibility of legal action to
motivate that.

Especially if she had a good lawyer and I'd designed the system based on
internet advice.


Once again, you condemn ALL Internet advice indiscriminately. If you
really mean that, why not just go away?

You're missing the point. I do NOT condemn ALL internet advice.
I merely observe that 99% of it is crap and that people asking
questions have little hope of recognizing that 1% nugget of good stuff.
Even the other 99% is thought provoking and sometimes leads to
additional insight. But again, the newbie can't tell the good from the
bad. If he could, he wouldn't have had to ask the question.

This is not unique to the internet, but the anonymity and lack of
accountability does greatly magnify the effect. If people got salary
reviews based on their internet advice, there'd be a LOT less internet
advice.

Even in industry, fully half of us are below average. If "average"
were any damn good, there'd be a lot less consulting work.
That's a sobering thought when you're sitting in your doctor's office.

I'm sittin' in your office. We just missed the ship date cause the
product failed the safety test cause the stripe on the green wire was
the wrong color. And I'm tellin' you, "It's not my fault. Wireboy8
told me to use that color and poopscooper69 confirmed. Why would I need
to phone up UL to verify?"
You just lost your preformance bonus.
How sympathetic are you gonna be? As Donald Trump would say... ;-)

mike

--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[Tom MacIntyre]

On Fri, 02 Apr 2004 15:03:00 -0800, mike <spamme0@juno.com> wrote:

John Woodgate wrote:
I read in sci.electronics.design that mike <spamme0@juno.com> wrote (in
406C8A00.4080801@juno.com&gt about 'Grounding a chassis for line voltage
safety', on Thu, 1 Apr 2004:


There seems to be a dismissal of the requirement for certification of internal
fixtures etc.


What people have said is that *certification* is impracticable and
unnecessary, but ****safe design and construction**** is practicable and
**essential**.


While this is an economic reality for the company,
I'd hate to be the designer of the fixture that injured Suzy-production-worker.


So would I, and I wouldn't need the possibility of legal action to
motivate that.

Especially if she had a good lawyer and I'd designed the system based on
internet advice.


Once again, you condemn ALL Internet advice indiscriminately. If you
really mean that, why not just go away?

You're missing the point. I do NOT condemn ALL internet advice.
I merely observe that 99% of it is crap and that people asking
questions have little hope of recognizing that 1% nugget of good stuff.
Even the other 99% is thought provoking and sometimes leads to
additional insight. But again, the newbie can't tell the good from the
bad. If he could, he wouldn't have had to ask the question.

Your 99% observation would fall into the (not) 99% of wrong
information, I think.

Tom

 

[John Woodgate]

I read in sci.electronics.design that mike <spamme0@juno.com> wrote (in
<406DF124.50402@juno.com&gt about 'Grounding a chassis for line voltage
safety', on Fri, 2 Apr 2004:

I'm sittin' in your office. We just missed the ship date cause the product
failed the safety test cause the stripe on the green wire was the wrong color.
And I'm tellin' you, "It's not my fault. Wireboy8
told me to use that color and poopscooper69 confirmed. Why would I need to
phone up UL to verify?"
You just lost your preformance bonus.
How sympathetic are you gonna be? As Donald Trump would say... ;-)

Not sympathetic at all. That sort of information is in standards; it
isn't something you NEED to, or SHOULD, ask on the net. Of course, if I
kept the standards locked up in my office, so that people couldn't see
them, the mistake would be my fault.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[KR Williams]

In article <406C86D6.6040707@juno.com>, spamme0@juno.com says...

I waste a lot of time reading newsgroups. I find that virtually ALL
(as in high percentage) internet advice is CRAP.

Then why are you here? By your own admission you're wasting your
time. Go away, no one will care. Honest!

--
Keith