Commercial fridge is blowing the fuse in panel all of  a sudden. Nothing has changed. Is it the fridge or panel?

The best thing to do is to Google
make model spare parts,
or
make model parts schematics.

If it was a fuse, it would blow and not run again. They do have a device called a 'clixon' that senses overheating. It could also be a faulty Run Capacitor. There is a relay for the compressor according to this.

https://www.google.com/search?q=imperial+heavy+duty+commercial+freezer+cuts+out

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Ask this company through there ebay auction.
https://www.ebay.com.au/itm/EUROTAG-2-DOOR-1000L-COMMERCIAL-UPRIGHT-DISPLAY-FRIDGE-BRAND-NEW-1YEAR-WARRANTY-/121133628429

But I would guess that the front panel comes off to locate electric and thermostat parts.

You may have accidently disconnected something.

YOU MAY HAVE BLOCKED THE VENTS IF YOU PULL THE STEREO OUT DO THEY WORK

Did you check the high limit thermostat?

You will need to adjust the thermostat.
The thermostat will be hidden at the bottom back of the fridge near the compressor.
You may need a screw a flat blade driver driver to adjust the themostat

check continuity of winding of internal fan by using ohmmeter if no continuity read replace fan.also inspect the bushing and shafting if stock up apply lubricant or replace new fan.also check the connections if had a fuse busted replace it with new one

This may sound too simple. A fuse is a safety. It usually blows when the amps are higher than the fuse rating. Since yours blows immediately, I would look very closly for a pinched wire, a crossed wire, or a wire that has rubbed through. Once that is eliminated, start isolating components one at a time. Check their web site. It's pretty good. Also, their tech support line is pretty good. It's worth the wait. 1-800-233-1940.

Change your cycling thermostat. When your cycling thermostat fails, then the reponsibility of your heating element to shut down goes to the high-limit thermal shut off (closest to heat element) and the thermal fuse. Your cycling thermostat should shut down heat element when it detects about 140* air in the blower housing. Yours can't detect that anymore so it lets your dryer heat up and up till you blow the thermal. new cycling thermostat and thermal

yes there's a ballast. on the top of fridge where you put the lights for the sign if you remove the plastic cover there should be a couple of them there.