<html>
<head>
<style><!--
.hmmessage P
{
margin:0px;
padding:0px
}
body.hmmessage
{
font-size: 10pt;
font-family:Verdana
}
--></style>
</head>
<body class='hmmessage'>
Not to keep the discussion going, but I haven't seen this morsel of input...<br><br>I am told that a Transfer Switch also is constructed to prevent an arc-welded contact from keeping the circuit live. With standard circuit breakers (like the 100A "mains" breakers in a typical home panel), there is a small but non-zero chance that opening the breakers will not actually open the circuit due to a failed contact. There is pretty much no way to detect that this has occurred, until you've killed someone upstream.<br><br>Greg KO6TH<br><br><br>> From: k7ftp@k7ftp.net<br>> To: aprssig@tapr.org<br>> Date: Mon, 8 Feb 2010 15:14:28 -0700<br>> Subject: Re: [aprssig] Snow, Back-feed, Shocking things<br>> <br>> From: "Tom Mandera" <tsm1@tmcom.com><br>> > How is a transfer switch significantly different from disconnecting the <br>> > main breaker (which could have failed and be passing electricity even when <br>> > off, but uncommon) before plugging on the backup power?<br>> <br>> A real transfer switch employs a BREAK BEFORE MAKE architecture. Either the <br>> generator is connected to the circuit, nothing is connected to the circuit, <br>> or the utility is connected to the circuit. Really a DPTT with a center off <br>> position.<br>> <br>> A real transfer switch connects between the house circuit breaker panel and <br>> the circuits that can be generator powered. When they are properly <br>> installed, they guarantee that you can't backfeed the utility and <br>> potentially cause problems (or death).<br>> <br>> Here is a link to an installation of a real transfer switch.<br>> <br>> http://www.empreputah.com/gentran.htm<br>> <br>> Personally, I believe that we have way too many laws and restrictions in <br>> this country, but that there are things that are SMART to do. We shouldn't <br>> legislate them, but our elected officials (and the appointed ones they <br>> select) love to try to legislate away all stupidity and carelessness, and <br>> they usually legislate away all of the freedom in the process.<br>> <br>> But like I said - there are things that are SMART to do. Electricians don't <br>> use MALE plugs as power SOURCES because of the exposed contacts. FEMALE <br>> receptacles are used for SOURCES because the contacts are protected - <br>> reducing the likelihood of someone getting shocked. The setup that Bob has <br>> created is acceptable as long as BOB is the one working with it and he <br>> ALWAYS does it correctly. If he doesn't, or if someone else is working with <br>> it, the likelihood of a problem is GREATLY increased.<br>> <br>> Let's compare this with the rules of firearm safety. <br>> http://www.jeepgunner.com/gunsafety.htm<br>> <br>> TREAT EVERY FIREARM AS IF IT IS LOADED<br>> <br>> NEVER ALLOW THE MUZZLE TO POINT AT ANYTHING YOU ARE NOT WILLING TO DESTROY<br>> <br>> KEEP YOUR FINGER OFF OF THE TRIGGER UNTIL THE FIREARM IS POINTED AT A TARGET <br>> YOU ARE PREPARED TO SHOOT<br>> <br>> If these rules are always followed, then the likelihood of injury or death <br>> in the event of a malfunction is little or none. If any one of the rules is <br>> ignored, the likelihood goes up. If two of the rules are ignored, they go <br>> up more. It's the same with this situation.<br>> <br>> There is a more practical standpoint on this. When I lived in Oregon, the <br>> local power utility would not start to work on the lines in an area if there <br>> was any sign of a generator in operation until someone had verified that the <br>> generator was incapable of being connected to a home - or that a transfer <br>> switch of the type I linked to above was installed and being used. If they <br>> found a setup like what Bob is using, they would not work on the lines in <br>> that area until it was disconnected and the cable used was "safed". Bob <br>> might have some very angry neighbors that are waiting for their power to be <br>> restored when they find out that he is the one holding it up while he argues <br>> with the utility company. While his setup might be safe as long as he is <br>> the one that sets it up and he does everything right, there is enough <br>> potential for issues that they would be within their abilities under local <br>> laws and codes to demand that he disconnect it and keep it that way.<br>> <br>> Just as a telco can disconnect any phone line which has problem-causing <br>> equipment attached, the power utility can do the same thing.<br>> <br>> In this case, there is a legal and affordable way to avoid the issue. I'd <br>> recommend it.<br>> <br>> Jim - K7FTP<br>> <br>> <br>> <br>> <br>> _______________________________________________<br>> aprssig mailing list<br>> aprssig@tapr.org<br>> https://www.tapr.org/cgi-bin/mailman/listinfo/aprssig<br> <br /><hr />Hotmail: Free, trusted and rich email service. <a href='http://clk.atdmt.com/GBL/go/201469228/direct/01/' target='_new'>Get it now.</a></body>
</html>