When a gfci breaker trips, it will throw the switch to a neutral position. OFTEN the enduser will slide the breaker handle back to the ON position "thinking" its ON; its not. You must throw the breaker handle FULLY to the OFF position to reset. You will hear a CLICK. Then throw the handle to the ON position. If you hear a CLICK when you do, your spa is tripping instantly; see below. If you don't hear a CLICK, push the TEST button and the breaker again will pop to the neutral position. Reset. If pressing the TEST does not trip the GFCI, you either have no power coming to the gfci OR the grci has failed.

To confirm you can remove the heater from the loop. First thing is to turn off the MAIN POWER SWITCH.

To isolate the heater depends on which model you have but in general. Most common all you do is unplug the canister heater from the side of the control box. If its a horizontal heater, remove the metal cover on the control box.

You will find 2 posts of the heater inserted through the control box from the heater. You will either disconnect the connection from the pcboard to the heater or the nuts holding the heater wires to the heater posts. To do so CAREFULLY remove the nuts holding the wire contacts to the heater posts. Be careful you don't bend the posts. On the heater posts are slots allowing you to install an open end wrench above and below the nut to apply torque without bending the posts. This is best but if you are careful you can remove the nut without bending the posts. Once you disconnect the wires make sure they are not touching anything.

Turn of Main power or GFCI breaker.

If the spa comes on and operates normally, and it usually does, replace the heater. Find the heaters at: HEATERS

Since it wasn't the heater, the remaining possibilities are few and rare.

First, look for water leaking onto the equipment.

Second is disconnecting pieces of equipment beginning with ozonator.

Third and rare is the pcboard itself damaged.

If not any of those, then consider the gfci or power to spa is compromise. To check, disconnect the wires from the incoming control box from the gfci. Make sure the hots and neutral are not touching anything. Then turn on power. If the gfci still pops, either the gfci or the line is shorted. See an electrician.

If the gfci doesn't pop, the failure is likely the pcboard itself or the transformer. Both of these failures popping the gfci is rare.

Warning: You will be working with live electrical current. If you are not experienced with electrical tests, refer this test to a qualified person.

NOTE: NEVER put a meter set to OHMS on a Live Electrical Spa; spa must be off.

Also, be careful not to touch any surface other than the surface you are testing with your meter probes or your own body.