I have a 60 amp 240V GFCI breaker that trips as soon as it is turned “on.”
I disconnected the black and red power lines coming out of it. When power is applied, it still trips immediately.
My only quick question: Have I definitively isolated this problem as a bad breaker? What else could cause it to trip with no hot load on it?
If there’s nothing connected to the load side, the GFCI shouldn’t trip, so it’s either wired up wrong or your GFCI is toasted.
It cannot be wired up wrong. It has worked for three months.
A secondary question: when a GFCI is “toasted” does it always fail-safe in this matter or could it sometimes fail deadly by staying open?
Yep, if it used to work, then it shouldn’t be wired up wrong. 
I didn’t know if this was a new install or not.
GFCIs manufactured prior to 2006 can fail in such a way that they still have their outputs energized but are no longer providing protection. GFCIs manufactured after 2006 must be designed to either fail safe or to give an indication that the protection has failed.
Outlet style GFCIs may have an LED indicating whether they are functioning properly or not. Breakers will typically fail safe and may also have a visual indication.
Excellent. By way of background, against all advice I was given here, I installed a hot tub last fall. I have a subpanel on the back porch with the aforementioned GFCI breaker as a main in the subpanel. Hot tub has worked great since October.
This past week, it got down to -15F here. I was in the hot tub on New Years Eve when it was -2F. It has since warmed up to about 30F. I went to check it last night and the GFCI breaker was tripped. There is a 20A 120V circuit in the panel and it was still on and functional (outlets are GFCI, breaker is not. ETA: on this smaller circuit).
I figured that I should have followed the advice here and not tried to do it myself (and maybe that will still be the case). However, I disconnected the red and black load wires from the breaker (note the white load was still connected). It still immediately trips.
I used my semi-limited electrical knowledge to conclude that there was simply no way that the breaker could trip unless it was faulty and therefore my wiring was spot on. 
Of course, no local hardware store stocks such a breaker, so I ordered it from Amazon. It will be here on Wednesday.
Lows are in the 20s, so I should not have to worry about any hard freezes in the tub or lines.
Why would a 3 month old breaker crap out? Are they not rated for -15F?
I assume you are talking about a GFCI breaker in a sub-panel. When you hooked up the sub-panel, did you make sure to separate the ground bus from the neutral bus? Not sure if that would pop a GFCI breaker though.
I didn’t realize you still had a wire attached.
If you’ve got current going through the neutral, that could be tripping it. Disconnect the white wire and see if it still trips.
Yes, separated. Thanks.
Well, the breaker is disconnected and sitting on the kitchen table. I am trying to picture how current would be going through the white wire when the red and black are disconnected.
Possibly shared the neutral with another breaker? Or tied a ground to it.
Unbalanced load is one possibility.
Agree.
Turn off the breaker. Disconnect the three load wires from the breaker (phase A, phase B, and neutral[sup]1[/sup]). Keep the other white wire (attached to the breaker) connected to the neutral bus. Turn on the breaker. It should not trip.
[sup]1[/sup]Don’t touch the copper when removing the neutral load wire. Because if there is a shared neutral you could get zapped.
One other possibility I would consider is:
The extreme cold resulted in condensation freezing somewhere that is now thawing and dripping on something in the hot tub cabinet. In other words, the GFCI is actually working as intended.
I’m confused. Which white wire should I disconnect? I have the white line in connected to the neutral bus. The load line is connected to the neutral bus. There is a white line from the breaker to the neutral bus.
The neutral from the main panel (white line in) should be connected to the neutral bus in the subpanel. The white wire from the breaker (the one permanently attached to the breaker) should also be connected to the neutral bus. The neutral to the load should not be connected to the neutral bus, there is a terminal on the breaker it should connect to.
From your description you have 2 of 3, not sure why it ever worked.
Here’s a good figure.
As stated by Marvin the Martian, the white wire coming from the load (hot tub) does not connect the neutral bus inside the panel - it connects to the “load neutral” screw terminal on the circuit breaker. In the above diagram, this wire is labeled “LOAD NEUTRAL - OUTPUT.”
The coiled white wire coming from the circuit breaker does connect to the neutral bus inside the panel.
Marvin, the only thing I can figure is that the neutral wire to the load had no current previously (due either to a perfectly balanced load or no 120 V loads), and now for some reason there is current on it.
Update: Success. The new breaker fixed the issue. Regarding the neutral load: There is no neutral connection on the hot tub side (just red, black, and ground) so that probably was why it worked the other way. I connected the way I was supposed to this time just in case.
Many thanks.
