220 wiring for spa

[kzimmerman]

I recently ran a new line for my soon-to-be-delivered hot tub, and before they hook it up, I wanted to see if someone had an opinion what I'm seeing right now.

I have a fairly old house, and the main breaker panel was full, so we installed a "Spa Kit", which was basically a seperate box with a 50-amp dual pole GFI breaker already included. This runs to a 60-amp disconnect outside, about 10 feet from the tub, and then there is about

20-feet or so of remaining wire for the install.

Everything seems fine right now, until I throw the disconnect on, at which point it arcs at the main GFI in the house and trips the breaker and disconnect hard.

The hook-up seems pretty straight-forward, and I'm not sure what could be causing this. The bare end for the tub has been splayed apart a bit to make sure that the ends aren't touching. Is this happening because I'm not "terminating" the grounding wire at the tub yet??

[trader4]

"The hook-up seems pretty straight-forward, and I'm not sure what could

be causing this. The bare end for the tub has been splayed apart a bit to make sure that the ends aren't touching. Is this happening because I'm not "terminating" the grounding wire at the tub yet?? "

No. Sounds like something is wired incorrectly at the disconnect. Having the other end of the cable open and not connected to anything should not produce a GFCI trip.

[kzimmerman]

hmmm....it looks correct to me. The two hot wires from each run are connected correctly. The grounds are secure, and the neutrals are connected together.

[Beeper]

[Rob Jones]

Divide and Conquer!

Disconnect (completely) the 'disconnect box' from the box with the 50A GFCI breaker, then see what happens when you close the 50A GFCI breaker. That'll at least tell you where your trouble is...

rob

[Doug Miller]

Re-check your wiring. You have a dead short somewhere.

-- 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?

[Stormin Mormon]

Well, it's obviously something wrong. Might want to get a second opinion (in person, someone familiar with electric). Before you go too much further.

[Panos Popadopalous]

If you are not a qualified licensed electrician you are making a big mistake trying to wire up your hot tub.

You could hook up something incorrectly and wind up DEAD!

This is no "do-it-yourself" job for an amateur.

For example, did you connect the grounding bar in the GFI breaker to the proper place?

[Richard J Kinch]

Something to check: a half-high double-pole breaker on the wrong spot in the panel creates a dead short.

[Doug Miller]

How?

-- 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?

[Chris Lewis]

According to Richard J Kinch :

Actually, what it produces is a 120V circuit with two hot wire, and two breakers in parallel. Which won't do you a bit of good with a 240V load, because both legs of the load are at the same voltage - applying _zero_ volts across the load.

[HerHusband]

It sounds like a short somewhere. Helpful, eh? :)

Since the house breaker didn't trip until you threw the final disconnect, my guess would be the run of wire between the Spa GFI and the disconnect, or maybe the the final dangling wire at the end for the hot tub. (I assume the exposed ends aren't touching the ground or anything else?)

If you have a continuity meter, you should be able to disconnect the wires at each end and check for a short.

Assuming you have the circuit wired correctly (hot leads to breakers, ground to ground, neutral to neutral, ground bus is separated from neutral bus in the "spa pack"), my guess would be damaged wire insulation. Probably under a cable clamp at one of the boxes, or possibly under a cable staple or where it passes through an opening.

I had this happen once when I overtightened a cable clamp and damaged the wire insulation. This caused a short to the metal box and it tripped the breaker. Everything looked fine till I pulled the thing apart and really inspected the cable.

Easy to find with a meter, virtually impossible without one.

Anthony

[Richard J Kinch]

Which is to say, a dead short, thus zero volts by definition.

[Jimmie]

No, A dead short at this type of voltage would envolve large amounts of current. Connecting the same phase together at some point gives a difference of 0 volts but also no current and doesnt blow fuses..

[Doug Miller]

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?

[Chris Lewis]

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.

[Matt]

A Doug Miller Classic.

Doug, in all his infinite wisdom, and via his own words has stated he only gives info when the person asking appears to be knowledgable enough to handle it.

In this case, the OP wants to know if his breaker is tripping because he hasn't hooked up the ground to his Spa yet.

Doug, does this sound like someone who knows what he is doing? (And no offense to the OP, but sir, call an electrician, PLEASE).

You just told someone to look for a dead short in a 220v line to a SPA, for gods sake.

Doug, don't you think this is a bit of dangerous advice?

[Richard J Kinch]

Right, but the two conductors are still DEAD SHORTED TO EACH OTHER.

[Chris Lewis]

According to Matt :

Simply _looking_ for a dead short in a 240 line can easily be done without the line energized and is perfectly safe.

Testing something by deliberately inducing a main-lug-to-main-lug dead short isn't by definition.

[Richard J Kinch]

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.