220 wiring for spa

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Swords ! Clubs ! Guns ! Knives !
C'mon guys, drop the war of words and REALLY go at it ! Lets see some 'Gladiator' type action !

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(Chris Lewis) wrote:

Chris, you have to cut Richard a bit of slack. In case you're not familiar with some of his other posts, you should know that Richard comes from a planet where it's safe to drink gasoline and breathe carbon monoxide, but borax is a deadly poison. So it shouldn't be much of a surprise to discover that electricity works a bit differently in his universe, too.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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No, they're not. They're connected in parallel. It's not the same thing at all.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Doug Miller writes:

My definition of "shorted" is an unintentional low-impedance connection. Dunno what yours is.
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Mine is "an unintentional low-impedance connection between an ungrounded circuit conductor and something that is grounded".
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Doug Miller writes:

OK, then you're being consistent with your definition, such as it is.
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It's certainly a more useful definition than one which equates parallel-connected wires with a short circuit. You certainly have some unusual ideas; apparently, the physics on your planet is as bizarre as the toxicology.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Doug Miller writes:

Yet yours requires a ground? Two hot phases can't short to each other?

The truth can seem bizarre, especially to the uncritical masses.
I think you hounds should take up a collection and dare me to swallow a shot of petroleum distillate. The jejune mockery ought to have stopped by now.
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Not if they're at the same potential, no.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Try again, Ace. A dead short is hot-to-ground, where there will be a large current flow. In the situation you describe, both conductors are at exactly the same potential. Therefore there will be no current flow between them, and thus it is not a short circuit; in fact, it's not a circuit at all.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Doug Miller writes:

Two hots can be dead shorted to each other, not necessarily to ground or neutral. This happens with the breaker misplaced as I suggested. And it causes problems if there is a backfeed somewhere down the line.
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Yes, they can - if the breaker is placed so that the two hots are on *opposite* legs of the service.

No, it does not. With the breaker positioned so that both poles are on the *same* leg of the service, the two hot conductors are at exactly the same potential. Connecting them together has no effect. Same potential = no current flow = no circuit = no short circuit.

Oh, really? Do tell. Where is this mysterious backfeed going to come from, and what sort of problems will it cause?
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Doug Miller writes:

Given that none of the usual explanations solve the observed behavior, the critical diagnostician will start eliminating the plausible but odd possibilities. I've seen this problem before.
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Uh, no.
Take two wires. Connect one end of each to the same hot wire.
Now measure the voltage difference between the other ends of the two wires you've added.
Zero right?
If you connect them together, what happens? Zip.
If you connect the two wires to the ends of a 240V heater, what happens?
Nothing. It stays cold, right?
Double-pole breaker with both sections on the same leg is the same thing.
It's not a short at all, it's simply paralleling the hot conductor.
A dead short of 240V is when the double-pole breaker has its sections on opposite legs, and _then_ you short the two hots together. That's the big bang.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
  Click to see the full signature.
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Chris Lewis writes:

If you connect them together, they are DEAD SHORTED. Whether anything "happens" doesn't change that fact.
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"If you connect them together, they are DEAD SHORTED. Whether anything
"happens" doesn't change that fact. "
But the fact is the OP had a problem where he gets an arc and trip when he closes a disconnect. That indicates a short causing high current. That can't happen because two hots on the same leg happen to be connected together, resulting in zero current flow. It has to be a short from the hot to either neutral or ground.
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Only with a single-fault hypothesis, which hasn't been tested.
Good diagnosis is hard.
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Wrong again.
If two points are at the same potential, it is _impossible_ for there to be any current flowing between them, without regard to the number or location of faults in the circuit.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Doug Miller writes:

By this principle, no shorted conductors can carry current.
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Wrong again.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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