Interlock locks to be used in lieu of transfer switch

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On Fri, 11 May 2007 18:02:20 -0000, snipped-for-privacy@nortelnetworks.com (Chris Lewis) wrote:

It's not a switch, it's an interlock. To be interfaced with the switch to prevent it closing unless the interlock bar is retracted. It thus becomes physically impossible to have both switches closed at once, since the switch must be opened in order to be able to extract the key and the key must be in the interlock in order to close the switch. Since there is only one key available, only one switch can be closed at a time... even if they are a mile apart.
Iggy's solution is far safer than the silly panels with switches linked together. Specifically, it is fail safe.
Mark Rand RTFM
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Mark Rand wrote:

It's only safe as long as someone follows the rules and there is only one key. You could just as easily leave out the key and just keep the rule, "Thou shalt switch OFF the one before you switch ON the other", which is nothing at all like a proper transfer switch.
Anthony
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On Fri, 11 May 2007 14:42:33 -0700, Anthony Matonak

I will put the second key in the bank safe deposit box. Or even throw it away.
i
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It won't matter. Any inpsector worth more than two pennies will reject a voluntary interlock.
wrote:

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On Mon, 14 May 2007 19:41:30 -0500, "Solar Flaire"

What do you not understand? an interlock is not voluntary. it is an interlock.
Mark Rand RTFM
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GB is an Inspector... in h i s head !
        /smirk
I would also echo your words in: ------
xxxxxx I had to state that it's use would be illegal in each of those installations. I'm not that bothered about safety except where the lack of it endangers people, then I get quite particular. ---------
This particular waste of tissue (human), Solar Fart//Gymmy//Bengi, calling itself by whatever - in issuing its own qualifications, is prime example of endangering persons who would take what they read as Gospel. Denying _it_ the space to spread the garbage it does is an Act of selfless Good.         cheers
        Ln
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Call it what you like..it won't pass inspection and therefore an illegal device.
or
You could get an Electrical Engineer to put his stamp of approval on the design documents and state it's specific usage...maybe. Apply to CSA or UL for an approval. You may have to submit a few prototype samples to get the approval though.
wrote:

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Last I saw (quite a while ago), CSA "type approvals" cost in the neighborhood of $10K. It may not have gone up now that UL and CSA are now more-or-less competitors in the same markets because of NAFTA.
[NAFTA meant that UL is more-or-less accepted in place of CSA in Canada, and vice-versa in the US (where the standards are equivalent).]
In Ontario, it used to be that you could get a "Hydro Inspector" (power utility) in to do a "unit approval" for $75. Which would stand in place of CSA approval for a single device. Subsequent copies had to be inspected independently. Intended for very low volume items. Ontario's power regulations have changed drastically and with the breakup the inspection agency is "ESA", and that is probably not available anymore.
If such a thing were available in the US, that's probably Igor's least expensive option.
CSA also lists certain engineering testing companies as approvers in place of CSA. NEC probably does as well. Eg: Warnock Hersey. But that's also largely intended for production runs, and it's not cheap.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
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You totally mised the point here.
Get the proper equipment and stop fooling with Linemen's lives.

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Er, what? I was agreeing with you.
--
Chris Lewis,

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Chris Lewis wrote:

His least expensive option might be to just use a readily available transfer switch which is already tested and approved, commonly used and quite suitable for the purpose.

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Yup.

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If the devices are installed properly, and _present_. How would they be installed? Bolted to the panel face plate? What if the plate has been removed?

Not quite. A large DPDT knife switch is failsafe.
--
Chris Lewis,

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Unless of course one blade comes loose from the handle and sticks in one position while the other blade moves to the other position. Some folks would notice that and probably do something about it, but a knife switch isn't 'failsafe'.
Designing relay and control systems to be truly 'failsafe' is a whole science unto its own. :-)
daestrom
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wrote:

That would not connect the generator to the utility, however.
i

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It would if the live fed through your house load and back fed the neutral from the grid.
message wrote:

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That's only one wire, and it's grounded anyway. The problem is more along the lines of if you're using a 240V circuit => you're backfeeding the grid's connected hot via the house load from the generator's connected hot. Plus the neutral => you're backfeeding half of the grid feed.
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That too but the neutral is only grounded (bonded) in one spot. It is not grounded everywhere and can and will carry current and can induce voltages in other parts of the circuits. This is why the neutral must be transfered also.

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Okay, okay. Sigh ;-)

Being in computer security, there's no such thing as failsafe, it's simply a matter of deciding how failsafe you want it compared to how much you're willing to pay for it.
--
Chris Lewis,

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Mark Rand wrote:

No point missed. He isn't engineering anything. He is trying to cobble stuff together to avoid the use of a proven, approved for the purpose and readily available DPDT transfer switch.
You design, test and submit for approval alternative devices when a suitable device is not manufactured.
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