Keeping going out to find the unit off..the little 20 fuse popped out. Push or hold it in and the unti cranks up again. As we're now in our first snow we are checking it twice a day...sometimes it's off...sometimes not?

Since we hooked it up last July it has been running fine...until about 2 months ago the ozonator cut out...we removed it electrically from the equation, but the unit worked fine for quite some time after that...

Any ideas?

for troubleshooting, disconnect and isolate both wires to the heater element. Try the spa overnight. If the breaker (not fuse i'm assuming) doesn't trip, replace the heater element.