Re: [PSES] UL Standards - Old School Spacings

[MIKE SHERMAN]

Doug --

Joe Musso, staff engineer at UL, might be worth contacting.

About 10 years ago I was is a similar position with what I considered an 
outdated spacings table in UL 1450. Joe was the staff engineer supporting 1450 
at the time.

What Joe suggested, and what ended up working out well, was adding UL 840 
(which is aligned with IEC 60664) as an alternate acceptable spacings 
requirement. This ballot item was easily approved and we never looked back.

So we sidestepped any discussion of the old spacings table, but Joe might know 
more about why he wanted to keep it and what its origins are.

Let me know if you need any language examples from the new section in UL 1450.

BTW, anyone can write a proposed change to any UL standard at any time---you 
don't have to be on the committee. Copying language from another approved UL 
standard (e.g., 1450) gets you off to a strong start.

And please share what you find out about these table values!

thanks,

Mike

> On 01/25/2022 12:26 PM Douglas E Powell  wrote:
> 
> 
> All,
> 
> I'm interested in learning the history behind what I call old school 
> spacings found in UL standards. In recent years there has been considerable 
> progress toward harmonizing UL spacings to international standards, derived 
> from IEC 60664-x. However, still today I encounter many UL standards with the 
> old spacings table (interpolation is not allowed).
> 
> > > 
> > Circuit Ratings
> > V
> > Minimum Spacings
> > Through air
> > Between parts of opposite polarity,
> > live and non-current carrying parts
> > and live and ground connections
> > mm (in)  Over surface
> > Between parts of opposite polarity,
> > live and non-current carrying parts
> > and live and ground connections
> > mm (in)
> > 30 - 50 1.6 (1/16)  1.6 (1/16)
> > 51 - 1503.2 (1/8)   6.4 (1/4)
> > 151 - 300   6.4 (1/4)   9.5 (3/8)
> > 301 - 660   9.5 (3/8)   12.7 (1/2)
> > 661 - 1000  19.1 (3/4)  19.1 (3/4)
> > 
> > > 
> I've had more than a few "discussions" with design engineers about tables 
> like this since the numbers seem very arbitrary, and I have to agree. The 
> most frequent trouble I have is trying to explain why an increase of just 1 
> volt over 300V results in such a large jump in the over surface requirements. 
> Usually I am forced to end with, "it is what it is, and we have to follow the 
> rules".
> 
> Any thoughts? 
> 
> -Doug
> 
> Douglas E Powell
> Laporte, Colorado USA
> doug...@gmail.com mailto:doug...@gmail.com
> LinkedIn https://www.linkedin.com/in/coloradocomplianceguy/
> -
> 
> 
> This message is from the IEEE Product Safety Engineering Society emc-pstc 
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> 

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Re: [PSES] UL Standards - Old School Spacings

[Douglas E Powell]

Hi Rich,

Yes, I obtained a copy of Mr. Stimper's book in 1995 and after learning it
is no longer published in English, I obtained permission from him to use it
in my own work; with proper attribution. This book is an excellent the
resource. I first learned my compliance with IEC, DIN-VDE and EN standards.
When I was finally exposed to UL standards it was somewhat discouraging and
felt like taking many steps backward. As a result of that experience, I
occasionally like to challenge the status quo.

I can't help but wonder if the old school UL spacings were somehow based in
industrial equipment for rather dirty locations.

All the best, Doug



On Tue, Jan 25, 2022 at 12:38 PM Richard Nute  wrote:

>
>
>
>
> Hi Doug:
>
>
>
> I don’t have any history.  But I do have data for how air behaves as an
> insulator and protection methods for creepage distances.
>
>
>
> The data for air insulation as a function of distance (2000 meters
> altitude) and field shape was given in IEC 664, first edition, 1980.  The
> data was not carried over to later editions.  The upper line is for a
> homogeneous field, the lower line for an inhomogeneous field.  I believe
> the changes in slope are due to anomalies in the measurement method (they
> should be straight lines).  The lines converge at about 327 volts, the
> Paschen lower limit for air.  (It makes no sense to require clearances for
> voltages below the Paschen limit!)
>
>
>
>
>
> Creepage distances were researched by Klaus Stimper, “The physical
> fundamentals of low-voltage insulation co-ordination,” VDE 57, 104 pages.
> I have this but it is too large a file to send by e-mail.  If you are
> interested in studying this text, I can make this available in Dropbox.
>
>
>
> Best regards,
>
> Rich
>
>
>
>
>
>
>
> *From:* Douglas E Powell 
> *Sent:* Tuesday, January 25, 2022 10:27 AM
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* [PSES] UL Standards - Old School Spacings
>
>
>
> All,
>
>
>
> I'm interested in learning the history behind what I call old school
> spacings found in UL standards. In recent years there has been
> considerable progress toward harmonizing UL spacings to international
> standards, derived from IEC 60664-x. However, still today I encounter
> many UL standards with the old spacings table (interpolation is not
> allowed).
>
>
>
> Circuit Ratings
> V
>
> *Minimum Spacings*
>
>
> *Through air*Between parts of opposite polarity,
> live and non-current carrying parts
> and live and ground connections
> mm (in)
>
> *Over surface*
> Between parts of opposite polarity,
> live and non-current carrying parts
> and live and ground connections
> mm (in)
>
> 30 - 50
>
> 1.6 (1/16)
>
> 1.6 (1/16)
>
> 51 - 150
>
> 3.2 (1/8)
>
> 6.4 (1/4)
>
> 151 - 300
>
> 6.4 (1/4)
>
> 9.5 (3/8)
>
> 301 - 660
>
> 9.5 (3/8)
>
> 12.7 (1/2)
>
> 661 - 1000
>
> 19.1 (3/4)
>
> 19.1 (3/4)
>
>
>
> I've had more than a few "discussions" with design engineers about tables
> like this since the numbers seem very arbitrary, and I have to agree. The
> most frequent trouble I have is trying to explain why an increase of just 1
> volt over 300V results in such a large jump in the over surface
> requirements. Usually I am forced to end with, "it is what it is, and we
> have to follow the rules".
>
>
>
> Any thoughts?
>
>
>
> -Doug
>
>
>
> Douglas E Powell
>
> Laporte, Colorado USA
>
> doug...@gmail.com
>
> LinkedIn <https://www.linkedin.com/in/coloradocomplianceguy/>
>
>
>


-- 

-Doug

Douglas E Powell
Laporte, Colorado USA
doug...@gmail.com
http://www.linkedin.com/in/dougp01

-

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Re: [PSES] UL Standards - Old School Spacings

[Richard Nute]

 

 

Hi Doug:

 

I don’t have any history.  But I do have data for how air behaves as an 
insulator and protection methods for creepage distances.

 

The data for air insulation as a function of distance (2000 meters altitude) 
and field shape was given in IEC 664, first edition, 1980.  The data was not 
carried over to later editions.  The upper line is for a homogeneous field, the 
lower line for an inhomogeneous field.  I believe the changes in slope are due 
to anomalies in the measurement method (they should be straight lines).  The 
lines converge at about 327 volts, the Paschen lower limit for air.  (It makes 
no sense to require clearances for voltages below the Paschen limit!)

 



 

Creepage distances were researched by Klaus Stimper, “The physical fundamentals 
of low-voltage insulation co-ordination,” VDE 57, 104 pages.  I have this but 
it is too large a file to send by e-mail.  If you are interested in studying 
this text, I can make this available in Dropbox. 

 

Best regards,

Rich

 

 

 

From: Douglas E Powell  
Sent: Tuesday, January 25, 2022 10:27 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] UL Standards - Old School Spacings

 

All,

 

I'm interested in learning the history behind what I call old school spacings 
found in UL standards. In recent years there has been considerable progress 
toward harmonizing UL spacings to international standards, derived from IEC 
60664-x. However, still today I encounter many UL standards with the old 
spacings table (interpolation is not allowed).

 


Circuit Ratings
V

Minimum Spacings


Through air
Between parts of opposite polarity, 
live and non-current carrying parts 
and live and ground connections
mm (in) 

Over surface
Between parts of opposite polarity, 
live and non-current carrying parts 
and live and ground connections
mm (in) 


30 - 50

1.6 (1/16)

1.6 (1/16)


51 - 150

3.2 (1/8)

6.4 (1/4)


151 - 300

6.4 (1/4)

9.5 (3/8)


301 - 660

9.5 (3/8)

12.7 (1/2)


661 - 1000

19.1 (3/4)

19.1 (3/4)

 

I've had more than a few "discussions" with design engineers about tables like 
this since the numbers seem very arbitrary, and I have to agree. The most 
frequent trouble I have is trying to explain why an increase of just 1 volt 
over 300V results in such a large jump in the over surface requirements. 
Usually I am forced to end with, "it is what it is, and we have to follow the 
rules".

 

Any thoughts? 

 

-Doug

 

Douglas E Powell

Laporte, Colorado USA

 <mailto:doug...@gmail.com> doug...@gmail.com

 <https://www.linkedin.com/in/coloradocomplianceguy/> LinkedIn

 


-

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Description: Binary data


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Re: [PSES] UL Standards - Old School Spacings

[Douglas E Powell]

Sorry all,

I knew the listserv would not support images, but since it regularly sends
me HTML email, I had thought it would allow tables in the body of the email
 .  Hopefully you'll still get the gist of the email.

~Doug

On Tue, Jan 25, 2022 at 11:26 AM Douglas E Powell  wrote:

> All,
>
> I'm interested in learning the history behind what I call old school
> spacings found in UL standards. In recent years there has been
> considerable progress toward harmonizing UL spacings to international
> standards, derived from IEC 60664-x. However, still today I encounter
> many UL standards with the old spacings table (interpolation is not
> allowed).
>
>
> Circuit Ratings
> V
> *Minimum Spacings*
>
> *Through air*Between parts of opposite polarity,
> live and non-current carrying parts
> and live and ground connections
> mm (in) * Over surface*
> Between parts of opposite polarity,
> live and non-current carrying parts
> and live and ground connections
> mm (in)
> 30 - 50 1.6 (1/16) 1.6 (1/16)
> 51 - 150 3.2 (1/8) 6.4 (1/4)
> 151 - 300 6.4 (1/4) 9.5 (3/8)
> 301 - 660 9.5 (3/8) 12.7 (1/2)
> 661 - 1000 19.1 (3/4) 19.1 (3/4)
>
>
> I've had more than a few "discussions" with design engineers about tables
> like this since the numbers seem very arbitrary, and I have to agree. The
> most frequent trouble I have is trying to explain why an increase of just 1
> volt over 300V results in such a large jump in the over surface
> requirements. Usually I am forced to end with, "it is what it is, and we
> have to follow the rules".
>
> Any thoughts?
>
> -Doug
>
> Douglas E Powell
> Laporte, Colorado USA
> doug...@gmail.com
> LinkedIn 
>


-- 

-Doug

Douglas E Powell
Laporte, Colorado USA
doug...@gmail.com
http://www.linkedin.com/in/dougp01

-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 


All emc-pstc postings are archived and searchable on the web at:
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Scott Douglas 
Mike Cantwell 

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Jim Bacher:  
David Heald: 

[PSES] UL Standards - Old School Spacings

[Douglas E Powell]

All,

I'm interested in learning the history behind what I call old school
spacings found in UL standards. In recent years there has been considerable
progress toward harmonizing UL spacings to international standards, derived
from IEC 60664-x. However, still today I encounter many UL standards with
the old spacings table (interpolation is not allowed).


Circuit Ratings
V
*Minimum Spacings*

*Through air*Between parts of opposite polarity,
live and non-current carrying parts
and live and ground connections
mm (in) * Over surface*
Between parts of opposite polarity,
live and non-current carrying parts
and live and ground connections
mm (in)
30 - 50 1.6 (1/16) 1.6 (1/16)
51 - 150 3.2 (1/8) 6.4 (1/4)
151 - 300 6.4 (1/4) 9.5 (3/8)
301 - 660 9.5 (3/8) 12.7 (1/2)
661 - 1000 19.1 (3/4) 19.1 (3/4)


I've had more than a few "discussions" with design engineers about tables
like this since the numbers seem very arbitrary, and I have to agree. The
most frequent trouble I have is trying to explain why an increase of just 1
volt over 300V results in such a large jump in the over surface
requirements. Usually I am forced to end with, "it is what it is, and we
have to follow the rules".

Any thoughts?

-Doug

Douglas E Powell
Laporte, Colorado USA
doug...@gmail.com
LinkedIn 

-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 


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formats), large files, etc.

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