On Sun, 13 May 2007 14:43:04 GMT, Howard Eisenhauer
wrote:

I'm coming in late on this, didn't see the original post but from
reading the replies I'm infering Iggy wants to use a couple of keyed
lock mechanical doohickies to prevent his genny breaker & mains
disconnect from both being "on" at the same time.

This is, everyplace I've ever been, perfectly legal as long as theres
only one key & it can only be withdrawn from the lock when the
doohicky has the breaker in the "off" position. I've had a number of
systems like this in sites where the feeds were physically seperated.

Now, that isn't to say I don't prefer a single changeover switch type
of deal, 'cause I very much do, but the keyed switchs are perfectly
acceptable if properly designed.

This has been discussed before somewheres on usenet, I remember
posting on it.

Yes, a "Kirk Key®" interlock is legal - but ONLY where access is
restricted to trained and responsible personnel like at power plants
and industrial buildings. People who know what will happen if they
screw up, and that they'll be held fully to account for it.

It is too easy to deliberately bypass that type of mechanical
interlock and cause a backfeed, as easy as unbolting the front panel
of the switchboard that the interlocks are secured to and operating
the circuit breakers out of sequence. Takes only seconds.

And there are too many fools who are ready and willing to do it out
of total and deliberate ignorance of the consequences.

For residential and light commercial/industrial applications where
the transfer equipment is not secured and can and will be operated by
untrained personnel, it HAS TO BE type accepted for that use. That
calls for a pre-packaged automatic or manual transfer switch of some
sort that has failsafes against backfeeds, and eliminates any "Kirk
Key®" type systems from consideration.

Unless you want to be up for multiple counts of Murder 2 for
backfeeding the utility service and killing a few workers on the line
gang, out trying to restore power after the storm...

-- Bruce --