Electrical code Compliance - Size of openings in enclosures

Author

Size of openings in enclosures

Erik Nielsen

2005-11-10, 10:21 am

Hello

I hope some of you experts can help me with this question. In my
company we produce medical instruments according to the IEC60601-1
standard. Many years ago one of our instruments was investigated by the
Canadien authorities and we were told that no opening in the bottom of
the enclosure could be more than 2.5 mm in any direction.
Regretfully, the recoding of the conversation with the authority no
longer exist and I am now trying to find out if this is really true. We
often put slits in the bottom of the enclosures for the purpose of
cooling the electronics and the instruments for Canada then get an
additionally grid inside to reduce the slits to small holes.
If such a requirement exists, could you please point to the relevant
standard and paragraph?

Thank you in advance,

Erik

hrhofmann@att.net

2005-11-13, 7:21 pm

Are you worried about finger pokings into the opening, or EMI coming
out ???? The authorities are worried about both!

H. R. (Bob) Hofmann

Erik Nielsen

2005-11-14, 7:21 am

Hello Bob.

I am not worried about either of these. We have, for the last 15 years
or so, produced instruments with an additional grid inside for the
Canadian market. For all other markets we don't have this grid. The
grid was put in there, in the first place, because someone from the
Canadian authorities (CSA) said it was required. I have tried to find
the paragraph that say this is required but without any luck. Maybe
that requirement no longer exist and I can get rid of the grid.
The slits we have in the bottom are small enough to prevent both finger
pokins and EMI coming out, so this is not a problem.

Thanks, Erik

hrhofmann@att.net

2005-11-14, 11:21 am

Erik:

Was the case of the original product metal or plastic? If everything
was plastic, then probably the concern was for finger-poking. If the
case was metal, it could have been either an EMC or a safety issue.
There is a "standard" finger that is used for Underwriter's
Laboratories safety testing, but I don't know anything more about the
size, etc., other than than it does exist.

I am in the USA and concerned with EMC and don't have any knowledge of
Canadian non-EMC requirements. Maybe you should post your question to
a product-safety newsgroup.

Regards,

Bob Hofmann

Geoff C

2005-11-14, 7:21 pm

"Erik Nielsen" <en@interacoustics.dk> wrote in
news:1131966180.529825.196630@g47g2000cwa.googlegroups.com:

> Hello Bob.
>
> I am not worried about either of these. We have, for the last 15 years
> or so, produced instruments with an additional grid inside for the
> Canadian market. For all other markets we don't have this grid. The
> grid was put in there, in the first place, because someone from the
> Canadian authorities (CSA) said it was required. I have tried to find
> the paragraph that say this is required but without any luck. Maybe
> that requirement no longer exist and I can get rid of the grid.
> The slits we have in the bottom are small enough to prevent both finger
> pokins and EMI coming out, so this is not a problem.
>
> Thanks, Erik
>

Possibly the reason is to reduce likelihood of burning embers/goo falling
through and starting a fire in the case of internal failure?

Erik Nielsen

2005-11-15, 9:21 am

Hi Geoff

Yes, this could be an explanation to the requirement and to the fact
that I have not been able to find it written anywhere. I have only been
thinking in the line of safety and of objects (like the corner of a
sheet of paper) entering the instrument.

Thanks for your input.

Erik

Erik Nielsen

2005-11-15, 9:21 am

Erik Nielsen

2005-11-15, 9:21 am

Hi Bob,

The case was metal. At that time (late 80's or early 90's) I don't
think it would have been an EMC issue. It is more likely to be a safety
issue. I am familiar with the test finger which comes in a stiff and a
jointed version, but none of them could enter the casing through the
slits which were about 3 x 25 mm. By the way, one of my older
colleagues remember that the requirement was not 2.5 mm but 1/16 of an
inch in either direction which is equivalent to 1.6 mm.
Maybe Geoff is right, that it is about preventing burning stuff from
falling out of the casing.

Thanks for your help.

Erik

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