Glass-door floral display fogging: which side, which fix

Wipe the inside of the glass with a clean dry cloth. If it stays wet, the fog is inside; if it dries and stays clear while the outside re-fogs, the fog is outside. Then read shop ambient: a Tampa Bay florist running 76°F shop air at 70% RH in July is at the dewpoint of cold glass — outside fog is a shop-environment problem, not a cooler problem.

All glass-door floral displays ship with anti-sweat heater wire embedded in the door frame and sometimes the glass itself. The heater is sized to keep the glass surface 1–2°F above shop dewpoint. If the heater has failed, gone unplugged after a service call, or been reset to "off" to save energy, the glass condenses every time shop humidity climbs.

Verify the heater current draw with a clamp meter at the door harness. Replacement heater wire kits run $140–280 plus labor. Do not run the cooler with heaters disabled in a Florida shop — the door frame will rot from sustained condensation in under three years.

Inside fog means warm humid air is entering the box and hitting cold surfaces. Three causes in cost order: a torn door gasket letting outside air in, a cracked door sweep, or an evaporator drain pan stuck flooded so condensate re-evaporates inside the box.

Pull the evaporator cover. If the drain pan holds standing water, the drain line is clogged with stem debris — clear with a wet vac or warm-water flush. This is a 20-minute fix that resolves a fog complaint that has been blamed on the compressor for months.

Beads of water on the door perimeter only — never on the main glass face — point at the door-frame heater. The frame heater runs lower wattage than the glass heater and fails first. Same diagnostic, same kit. Ignore for too long and the frame rusts from inside.

An overcharged unit runs the evaporator colder than design. The coil pulls too much humidity, dumps it as condensate, and the box internal humidity drops while surface temperatures get cold enough to fog. Diagnostic is manifold-gauge superheat reading — under 8°F superheat means overcharged. Recover, weigh, recharge to nameplate.

This shows up most often after a recent service call where a tech "topped off" the unit instead of weighing the charge. Insist on weighed charges and documentation on every refrigerant call.

If outside fog persists after door heaters are verified, the shop is too humid. A 10,000–14,000 BTU portable dehumidifier in the floral prep area pulls shop dewpoint down 5–10°F in summer, eliminating glass fog without touching the cooler. Capex $400–800; this is the cheapest meaningful fix that gets ignored most often.

Run shop-floor RH monitoring alongside ColdSentry on the cooler itself. If shop RH stays above 65% through summer, the dehumidifier is paying for itself in heater-wire life and cooler runtime.