RE: it's not all bad news

Posted by nsgarch (A) on May 4, 2009 at 08:59:08

In Reply to: RE: it's not all bad news posted by jea48 on May 4, 2009 at 08:09:41:

The shield in the Shunyata power cord is passive (does not connect to ground anywhere.) So as far as UL is concerned, it's no different (safety-wise) than a cord without a shield. So they give it the Shunyata cord a UL label, which just means you can't get a shock from touching (an accidentally exposed?) shield. The UL label doesn't imply better performance, but it's good marketing if one is trying to impress less knowledgable consumers.

At really high (RFI) frequencies, some feel passive shielding is as effective as a grounded shield. (I don't, but that's how I understand it.) Neither a floating (grounded at one end) or a passive shield (like Shunyata's) can conduct a current. This is good from a not-picking-up-hum standpoint.

The reason UL doesn't like floating shields (shields connected to ground at just one end) is because they're afraid that somehow (beats me how!) a consumer might inadvertantly complete the circuit between the floating end of the shield and ground, thus completing a circuit. And they (UL) are afraid that if there is any potential current that could flow through that newly completed circuit, it's going to flow through the consumer, poor thing!

It's just another 'cover your ass' manuver. . . . however,the FCC requires digital gear be supplied with a shielded power cord that IS connected to ground to make sure the digital equipment doesn't broadcast RFI. The only way to satisfy both the FCC and UL is to connect the shield at both ends. Otherwise the equipment manufacturer can't get a UL label for his priduct.

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Follow Ups Full Thread

Topic - Relevance of UL listing with power cords - Asrale 21:53:00 04/29/09 (19)

The only product recalls I've found - E-Stat 16:20:51 05/3/09 (0)

it's not all bad news - nsgarch 12:20:37 05/2/09 (6)

The Volex 17604 has shield grounded at plug end only. - Al Sekela 13:56:57 05/4/09 (2)

Al, can you tell me how you know that, because . . . - nsgarch 14:46:43 05/4/09 (1)

I know because I did tear them apart. - Al Sekela 14:55:38 05/5/09 (0)

RE: it's not all bad news - jea48 08:09:41 05/4/09 (2)

RE: it's not all bad news - nsgarch 05/4/0908:59:08 05/4/09 (1)

I did a test.... - jea48 08:36:03 05/7/09 (0)

Sorry the test was invalid....... - jea48 10:48:42 07/7/09 (0)

The only power cord I ever had fail was labeled as UL-listed. - Al Sekela 11:56:06 04/30/09 (0)

RE: Relevance of UL listing with power cords - jimmyjames 08:43:37 04/30/09 (0)

It's a money thing and electricians can't install non-UL things - Awe-d-o-file 07:46:49 04/30/09 (0)

Are the big boys UL listed? - chosenhandle 05:57:18 04/30/09 (0)

Although you have a point, - Dave Pogue 04:22:33 04/30/09 (6)

Horror Story - Dynaudio_Rules 09:11:15 04/30/09 (5)

RE: Horror Story - Glen B 13:17:04 04/30/09 (4)

NEC 2008 Arc Fault Protection. - jea48 08:31:28 05/4/09 (2)

it seems to me ... - gymwear5@hotmail.com 11:17:00 05/6/09 (1)

RE: it seems to me ... - jea48 08:38:45 05/7/09 (0)

RE: Horror Story - Dynaudio_Rules 14:05:43 04/30/09 (0)

Follow Ups

RE: it's not all bad news - nsgarch 05/4/0908:59:08 05/4/09 (1)

I did a test.... - jea48 08:36:03 05/7/09 (0)

Sorry the test was invalid....... - jea48 10:48:42 07/7/09 (0)

RE: it's not all bad news

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