As a general rule, overload conditions that are extreme enough to trip a circuit breaker are fairly rare.
However, it does happen.
If your fully self contained spa is tripping a 40 or 50 amp breaker, there are a few things to take into consideration.
1. Has the spa been worked on recently?
If so, then something has either been connected wrong, or in the case of an air control spa with conventional capillary style thermostat and/or high limit switch, the copper capillary tube from one of them may be touching a live conductor. In this case the capillary tube will usually be melted in half, and the source of the short may literally be blown away. In which case, you'll have to replace the thermostat or high limit.
You'll need to do some very diligent checking of the wiring connections to be sure that there are no offenders in this department.
On a recent service call, I found where a spa technician had re-installed an electric heater, and had connected the L2 line to the ground on the heater itself. This thing not only tripped the spa breaker, but was blowing the 200 Amp main circuit breaker of the entire house! Simply switching the wires brought everything back to normal. Pros can make the dumbest mistakes sometimes.... We all make them. Don't fall for the typical 'I know I did it right, there's nothing wrong in there'.... don't let your ego get the best of you. Double and triple check everything. One wrong wire is all it takes.
2. Is the main breaker getting warm?
If it is, check the temperature of the wiring... at least 8-12 inches away from the circuit breaker. If the wiring is getting warm also, then you've got an over-current condition. If the wiring's temperature feels normal... and not warm, then you've got a circuit breaker going bad, and/or, the circuit breaker wiring connections are loose. You could also have a circuit breaker that isn't seated properly on it's base connections. Check this out for more info.
It is normal for the copper wire to give way to the screw terminals over time, and to maintain good electrical contact, you must re-tighten them. Remember, there's a lot of current running through these connections, and if they are even the slightest bit loose, this bad connection will generate enough heat to fry even the best circuit breakers.
Sometimes, when making this correction, the circuit
breaker will still get warm. If this is the case, be prepared to replace the breaker, because
thermal damage has already occurred. If tripping continues, then what I do is replace the
circuit breaker with a brand new one, and then wait and see what happens. In virtually every
case, the new breaker is all that is required.
3. Last effort, the ditch of troubleshooting... time to think.
And I mean like... flip the breaker and it immediately goes into the tripped position. Not after 5-15 seconds, but immediately. You don't even have enough time to remove your hand from the breaker.
You've got a dead short somewhere. Try unplugging your pump motor from the spa control pack. If the tripping stops, then you've found your problem... a short inside the motor. It's time to replace it.
Otherwise, turn your thermostat all the way down. If it doesn't trip, then you've usually got a shorted heater element.
Still no solution? Check for bad/burned wiring in the spa control pack or heater.
Tripping after a few seconds of switching on... (1 to 3 seconds)
Like the above, turn your thermostat all the way down. If tripping ceases, then you've probably got a shorted heater element.
Turn the thermostat all the way down. If the condition repeats, then you may have a bad circuit breaker, or a defective pump.
However, be sure that your circuit breaker is properly sized for your spa. Most self contained spas working on 115 volt power require a DEDICATED 20 amp breaker. If you're sharing the circuit with other components.... then you're not set up right. Don't increase the present breaker sizing, this can be dangerous. Get your system set up correctly with a dedicated 20 amp 10 gauge circuit. Then try troubleshooting this again.
If your spa is connected using a 30 amp 230 volt circuit, then it may be undersized. Double check your spa's ratings for the proper circuit sizing.
Double check the temperature of the circuit breaker and the wiring, away from the breaker itself. Don't forget that circuit breakers go bad, and there is usually a reason for it. In most cases, it's heat damage from wiring connections not being tight enough.It trips, and you don't know when... it's just very infrequent.
Circuit Breaker trouble. Most likely and most frequently found situation with an ornery circuit breaker like this. The breaker is getting warm, and it takes a long time for it to eventually trip. No scientific explanation will do any justice here... just experience. Bad connections....
Otherwise, it's going to be a pump motor or a heater element.