While trying to get a hot tub up and running, I have a breaker problem.


With any connection with 120V (using a line and neutral wire), the
breaker trips.

If I only connect 240V connections, being the pump and the heater, with
the contactor and pressure switches bypassed, the tub runs and heats
up.

On 120V, there is only a light bulb, and a contactor, which is fed
through a pressure switch and limit switch.

If either of the two, light / contactor, are connected to 120, the
breaker trips.

The possibilities I see a
1. Both the light circuit, and the contactor are shorted to ground.
2. The electrician who installed the 240V circuit did something
strange.

I am having trouble beleiving both circuits are shorted, that would be
too much of a coincident.

I do not completely understand 240V breakers. Could I have a version
that requires complete current balance on 240V? If only 240V
connections are attached, there should be no current on the neutral
wire. This case runs fine.

In the event 120V is connected, current (a small amount) should exist
on the neutral wire.

Why is the breaker tripping???

I suppose my next step could be to detach the wiring from the tub, and
just try to power a lamp or something to ensure it is nothing in the
box...