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 Post subject: Conversion error in CSA Z462-08 Annex D?
PostPosted: Wed Mar 04, 2009 7:10 am 
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Joined: Tue Feb 24, 2009 7:05 am
Posts: 252
Hello there,

In equation D.5.2(a) of Annex D of CSA Z462-08, the exponent of D_A is -0.9246. In equation D.5.1(a) of Annex D of NFPA 70E 2009, it's -1.9593. The two following sample calculations give the same Incident Energy given the same input data.

All this seem OK, until you try some other value of D_A with both equations. Then you don't get the same results.
Somebody fuddled with the exponent of D_A so the sample calculation worked out OK, but you can't do that as all other values of D_A won't give you the same results.

I propose the following to replace equation D.5.2(a) of Annex D of CSA Z462-08:
E_MA = 5271 x 25.4^1.9593 x D_A^-1.9593 x t_A x [0.0016F^2 - 0.0076F + 0.8938]
which could be simplified in
E_MA = 2981000 x D_A^-1.9593 x t_A x [0.0016F^2 - 0.0076F + 0.8938]

Also, in CSA Z462-08, the definition of D_A for equation D.5.2(a) says it's in inch, when it should be in mm.

The same conversion mistake has been made in equation D.5.3(a) of CSA Z462-08. I propose the following to replace equation D.5.3(a) of Annex D of CSA Z462-08 (once simplified):
E_MB = 587460 x D_A^-1.4378 x t_A x [0.0093F^2 - 0.3453F + 5.9675]

Any comments on this?
To who should I report this?


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PostPosted: Wed Mar 04, 2009 7:34 am 
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Joined: Tue Feb 24, 2009 7:05 am
Posts: 252
A typo this time...

In D.7.3 of Annex D of CSA Z462-08, the definition for K says:
Quote:
K = -0.153 for open-air arcs
K = 0.097 for arcs in a box

In D.7.2 of Annex D of NFPA 70E 2009, the same definitions for K says:
Quote:
K = -0.153 for open-air arcs; -0.097 for arcs-in-a-box


I don't have IEEE 1584 to compare what that standard says.

To who should I report this?
Thanks.


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PostPosted: Thu Mar 05, 2009 11:45 am 
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Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
1584 agrees with 70E.


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PostPosted: Thu Mar 05, 2009 11:57 am 
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Joined: Tue Feb 24, 2009 7:05 am
Posts: 252
So CSA Z462-08 is in need of a correction.

I'll look into how to do this.


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PostPosted: Sun Mar 22, 2009 9:26 am 
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Joined: Sun Sep 23, 2007 5:00 pm
Posts: 114
Location: Calgary, Alberta, Canada
Vincent:

I am on the CSA Z462 Technical Committee, next meeting is in Regina, April 1-2.

We are treating all comments as formal requests for clarification, we need this to happen.

Can you email me your comments so I can follow up formally

Regards;
Terry Becker
http://www.esps.ca
[email protected]


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PostPosted: Mon Mar 23, 2009 5:27 am 
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Sure Terry. I'll do it so we get a better CSA Z462 in the end, one we can trust.


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