Glass-door dairy and beverage cases in Tampa Bay grocery stores depend on anti-sweat heaters in the door frames and mullions to prevent condensation. When they fail open you get fogged glass, dripping water, and a slip hazard; when they fail on you get a $4,000-a-year energy waste per case. Both are diagnosable in five minutes.
Anti-sweat (anti-condensate) heaters are low-wattage resistance elements built into the door frames, mullions, and sometimes the glass itself on glass-door display cases. They keep the surface above the dew point of the surrounding store air. In Tampa Bay grocery — sales floor RH commonly 55–65% even with HVAC — without anti-sweat heat, every glass door and frame on every dairy case fogs over within 20 minutes of doors-closed time.
Symptom: visible fog or condensation on the door frame or glass, water on the floor under the door. Test: at the case junction box, ohm out the heater circuit. A cold heater should read 50–500 ohms depending on wattage and the number of elements in series; an open circuit reads infinite. Replace the failed element — most anti-sweat circuits are field-replaceable without pulling the case.
Less common but happens after long Tampa Bay service. Heater element insulation breaks down, draws ground fault, trips the GFCI feeding the case lighting/heater branch. Symptom: case lighting and heaters out together, GFCI tripped. Replace heater, retest insulation.
Modern cases include anti-sweat heater controllers that pulse-width modulate the heaters based on store dew point — typically 10–60% duty cycle in normal grocery operation. If that controller is missing, bypassed, or stuck at 100%, the heaters run 24/7 and consume 4–8 kWh per case per day above what's needed.
Diagnostic: clamp the heater circuit at the junction box. If amp draw is steady at full load all day with no modulation, the controller is bypassed or failed. Common across older Hussmann, Hill Phoenix, Tyler, and Kysor Warren installs from before 2010 — many cases shipped with the controller as an option that wasn't ordered.
A typical 5-door dairy case has roughly 700–900W of total anti-sweat load. Always-on at $0.13/kWh (current Tampa Bay commercial blended rate): roughly $800–$1,000 per case per year. With proper dew-point control reducing duty cycle to 25%: $200–$250 per case per year. Across a 25-case dairy and beverage lineup, retrofitting dew-point controllers saves $15K–$20K per year in pure energy.
Multiple manufacturers (Cool-Gard, Doorganizer, ECT) make field-installable anti-sweat heater controllers that read store RH and dew point and modulate the heater circuits across an entire lineup. Installed cost: $400–$700 per door circuit. Payback at Tampa Bay store conditions: 12–18 months.
For new installs, all current Hussmann, Hill Phoenix, and Anthony glass-door cases ship with integrated anti-sweat control as standard — verify it's enabled at commissioning.
If anti-sweat heaters test good but doors still fog, the next suspects are: (1) door gasket failure causing humid sales-floor air to leak into the case, raising internal dew point — gasket replacement; (2) sales floor RH above 65% — HVAC fix, not a case fix; (3) door cycling so frequent that the case can't recover — operational change.
Most often a failed anti-sweat heater in the door frame or mullion. Ohm out the heater circuit at the junction box — an open reading confirms a failed element. Less commonly the cause is a failed door gasket or sales floor humidity above design.
A typical 5-door dairy case has 700–900W of anti-sweat load. Running 24/7 instead of properly modulated wastes roughly $600–$800 per case per year at Tampa Bay commercial electric rates.
Yes. Field-installable anti-sweat heater controllers from multiple manufacturers retrofit to existing case lineups for $400–$700 per door circuit and typically pay back in 12–18 months at Tampa Bay store conditions.
55% RH or below at 72–75°F is the design point for most glass-door display case manufacturers. Above 65% the anti-sweat heaters can't keep up and you'll see persistent fogging regardless of heater condition.
Suncoast Cold Systems handles exactly this kind of commercial refrigeration issue across Tampa, St. Petersburg, Clearwater, Brandon, Riverview, Temple Terrace, and Wesley Chapel. 24/7 dispatch. Licensed Class A A/C Contractor (FL #CAC1824642), EPA 608 Universal, OSHA 30 Construction.
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