THE INSTA HOT HEATER KEEPS TRIPPING THE BREAKER?

You water heater most likely has a shorted heating coil, don't run it like this, call a service technician.

Replace the limit, by tripping often they become even more likely to nuisance trip.

http://waterheatertimer.org/Water-heater-is-tripping-breaker.html

Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Copy following link for troubleshoot walk-thru for electric water heater tripping breaker:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#trip-breaker

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Thermostat could be bad causing the breaker to trip due to it being shorted. It's either your breaker or the thermostat, more than likely the upper thermostat is bad.

You had an instant heater there before? Or a different type? Your breaker numbers don't mean anything to me, I need amps and volts, what is the amp? 30? and the volt is 220? Or are you in Europe?. And you had the four wires in there before? And you have all 4 wires on the heater line? And the heater is grounded? It should work. Unless it is not getting enough juice, but you already upped the amp. Let me know what you got.

Tripping off at the water heater or at the breaker box?

replace the t stat

Is this a new install or is this something that has just come up? If it is a new install, the amperage on the breaker is too low. You will have to call an electrician to come in and check to see if the romex wire is large enough to handle a higher amp breaker. If not, it could be that the breaker has become weak and tripps prematurely. If it's not the breaker its self then the heating element is bad on the unit.