I got a call from a meat market customer Thursday at 5:30 AM shortly after the deli kitchen crew came in. They said the store had a burning smokey odor and the 3-door reach-in freezer was making loud popping sounds and flashes of light.
Fortunately, they managed to find the breaker for that case and shut it down. I arrived a while later to find this:
Note the melted temperature control knob:
Lot's of smoke staining too. (Yes, that's one of my TEV conversions):
The product on the lower four shelves was still hard frozen. The stuff on the top shelf was not only thawed, but actually cooked.
Can't figure out what the heck this fuzzy crap is on the doors:
Got the coil plenum down to see what was going on up there. Note the insulation dripping from that brown wire:
Then I found the source of the terribly acrid smoke. The melted wiring had shorted to the evap coil blowing several pounds of R404A and a bunch of POE oil into a glowing maze of defrost heater elements. It's hard to see, but there's a hole in the top front return bend.:
Of course all this fried wiring goes up into the box insulation in the top and ends up down at the right front bottom of the box. No repairing that.
How did this happen? This case had no defrost limit thermostat. I'm still not sure how it all started, but it certainly wouldn't have gotten this far if the case were designed to have a safety limiter for the heaters. (It has one for the door frame heaters but not the defrost heaters....go figure)