I do residential, so I was just at a gas station I frequent. He asked me to look at his cooler. Complaint was freezing evap. He turned off the unit the night prior. Pan full of water, so I vacuumed out. Coil was icing up immediately. WR defrost with sencing bulb set at +30 whatever that means. Drain mustbe stopped up, but I suspect the defrost Iis not Iinitiating or not running long enough. But what do I know. R-502 frezone. I passed it to a buddy that can do low and med refrigeration. Know when to say nope.