When a multi-deck open case at a Tampa Bay grocery store stops holding 38°F, the cause is almost always one of six things — and the right diagnostic order saves hours of guessing and thousands in lost product.
Open multi-deck cases (Hussmann Impact, Hill Phoenix Reveal, Kysor Warren KillerCold, Zero Zone Crystal Merchandiser) hold temperature with an air curtain, not a closed door. The discharge nozzle at the top blows chilled air down across the product zone; the return grille at the bottom pulls it back in. If anything disrupts that laminar curtain — overstocked product above the load line, missing or warped honeycomb, blocked return grille, store HVAC discharging directly across the case face, customer fans aimed at the aisle — the case will run warm regardless of how cold the coil is.
Before any other diagnostic, walk the case at eye level. Confirm product is below the painted load line. Confirm the honeycomb at the discharge is intact and not crushed. Confirm the bottom return grille is clear. This catches roughly a third of "the case is broken" tickets at no cost.
Tampa Bay grocery stores pull warm humid air across evap coils all day. Dust, grease aerosol from nearby deli ops, and produce dust pack the fins on the discharge side. A coil that looks 30% dirty visually is usually 50–60% reduced in airflow, which raises product temp 4–8°F.
For rack-served cases, the remote condenser on the roof is the other half of this story. A south-facing rooftop condenser fouled with palm pollen and Florida construction dust loses condensing capacity exactly when ambient is at its worst. Both should be on a quarterly clean schedule for any Tampa Bay store, not the manufacturer's stock semi-annual.
Open multi-decks are scheduled for 2–4 electric or off-cycle defrosts per day depending on the application. A failed defrost heater, stuck contactor, or out-of-calibration termination thermostat lets ice build on the coil shift over shift. By the third missed defrost, airflow is choked and the case runs 6–10°F over setpoint with a coil packed in frost.
Tell from the front: pull a panel and look at the coil. Solid frost across the face after the next scheduled defrost cycle (check the case controller log) tells you the defrost system, not the refrigeration loop, is the problem.
Electronic expansion valves on rack systems (Danfoss AKV, Sporlan SER) and mechanical TXVs both fail in two directions. Starved: low superheat alarm, coil partially active, half the case warm. Flooded: liquid back to the suction header, oil dilution at the rack, eventual compressor damage. Pull case suction superheat at the case junction box and compare to the manufacturer's spec — typically 4–8°F for medium-temp open multi-decks.
If the EEV is hunting (oscillating open and closed), the discharge air sensor or the case controller (CPC E2, Danfoss AK-CC, Emerson EC2) is usually the issue, not the valve.
On a parallel rack supplying multiple cases, a slow leak shows up first as one case running warm — usually the case furthest from the rack, with the longest line set. Receiver level dropping, low discharge pressure on the rack, and superheat climbing across the affected cases together point to undercharge.
Florida rack systems have a hard problem here: refrigerant is expensive and tightly tracked under EPA 608 §82.157 leak repair rules. Any rack over 50 lbs of refrigerant with documented leaks above 20% annual leak rate triggers mandatory repair within 30 days. Don't top off and walk away — find the leak.
If multiple cases on the same suction group are running warm together, the issue is upstream — at the rack. Common causes: a failed compressor on a parallel-3 or parallel-4 rack (you've lost 25–33% of capacity), a stuck unloader, a failed crankcase pressure regulator, a fouled liquid line drier causing excessive pressure drop, or a controller calling wrong setpoints after a power event.
This is rack-tech work. Anyone who has only worked on self-contained reach-ins will not have seen these failure modes.
In Tampa Bay summer, supermarket relative humidity at the sales floor commonly runs 55–65% even with HVAC trying. Multi-deck case manufacturers spec maximum store conditions at 75°F / 55% RH. Above that, the air curtain begins to entrain moist store air, the coil works overtime to dehumidify it, and the case can't hold setpoint at any compressor capacity.
The fix is rarely on the case — it's HVAC. A grocery HVAC tune-up to lower sales floor RH back under 55% will recover 3–5°F of case temperature on the worst-performing decks.
After every named storm or extended outage, we see a wave of "case not cooling" calls that trace back to controller corruption from dirty restarts, tripped overloads that didn't reset, or one compressor in a parallel rack that came back motor-locked. If your case started misbehaving within 72 hours of a power event, look at the rack first — not the case.
Most often the air curtain is being disrupted — overstocked product above the load line, store HVAC blowing across the case face, or a blocked return grille. Check those before any refrigerant work.
Quarterly minimum on both the evaporator coils and the rooftop condensers. Florida humidity, palm pollen, and construction dust foul coils much faster than the manufacturer's stock semi-annual schedule.
Product temperature ≤41°F per FDA Food Code 3-501.16, with a typical setpoint of 34–38°F discharge air. Deli prepared foods cases run the same. Frozen multi-decks run 0°F product, -10 to -20°F discharge.
Usually not. Cases warm at one end almost always have a coil airflow issue — partial defrost failure, drain blockage, or honeycomb damage at that end. EEV starvation is a less common second cause.
Under 40 CFR §82.157, commercial refrigeration systems with full charge ≥50 lbs that exceed a 20% annual leak rate must be repaired within 30 days of discovery, with verification testing required.
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.
When a coil packs with ice, the defrost system is usually the suspect. Diagnostic order, cheapest to most expensive.
The decision drives 20 years of operating cost and a third of your build budget. Real numbers.
What a real quarterly walk looks like — case-by-case, rack-by-rack, with the Tampa Bay calendar baked in.