How an open multideck holds temperature
A multideck has no door. Instead, a fan blows cold air out of a grille along the top front edge and down across the open face to a return grille at the bottom. This curtain of air separates the cold shelves from the warm aisle. Some of the cold air spills into the store and some warm, moist store air is pulled in, so the cabinet is constantly cooling and drying incoming air. Anything that disturbs the curtain — a ceiling fan, an AC diffuser blowing at it, stock pushed past the shelf edge — lets more heat in.
Store conditions decide whether it works
Open multidecks are designed for air-conditioned retail floors. In a warm, humid store the curtain draws in far more heat and moisture than it was designed for: coils frost faster, shelves run warm and the floor in front can become wet with condensation. Before buying, ask the supplier at what room temperature and humidity the cabinet was tested to hold its stated product temperature, and compare that with your store on a monsoon afternoon.
- Keep multidecks away from entrance doors, shutters and sunlight.
- Do not place AC outlets or ceiling fans so they blow onto the open front.
- Allow aisle width for shoppers and trolleys, plus room for staff restocking.
Plug-in or remote refrigeration
| Plug-in / integral | Remote | |
|---|---|---|
| Where the condensing unit sits | Inside the cabinet | Outside, on a roof or in a plant area |
| Installation | Place and plug in; easy to move | Refrigerant piping, drains and electrical work |
| Heat in the store | Rejected into the sales floor, adding to AC load | Rejected outside |
| Noise | Compressor noise on the floor | Quieter sales floor |
| Best for | Smaller stores, few cabinets, frequent layout changes | Long line-ups in larger stores |
Load lines and merchandising
Every shelf has a maximum fill line, often marked. Stock pushed beyond it or stacked above it blocks the air curtain and warms the whole cabinet, not just the overloaded shelf. Train staff to keep within the lines and not to place product on top of the cabinet or in front of the return grille. Price-tag rails and promotional wobblers should not hang into the air path.
Cutting running costs
- Night blinds pulled down at closing reduce cold loss sharply while the store is shut.
- LED lighting adds less heat than fluorescent tubes.
- Efficient fans and well-maintained coils reduce power draw.
- Glass doors fitted to a multideck cut energy use considerably, at some cost to impulse sales; many stores now use doors for dairy and keep produce open.
- Clean honeycomb grilles and return grilles so the curtain stays even.
What belongs in an open multideck
Open cabinets suit fast-turning chilled products: milk, curd, packaged dairy, juices, fresh produce, salads and ready-to-eat items. They are less suitable for stock that needs very tight temperature control or sits for days. Fruit and vegetables generally tolerate a slightly warmer band than dairy and ready meals, so place them in cabinets set accordingly rather than mixing everything in one line-up.
Defrost and drainage
Because an open cabinet constantly takes in moist store air, its coil collects frost quickly and defrosts several times a day. During defrost the product temperature rises slightly, so the schedule should be set to avoid peak trading where possible. Meltwater has to go somewhere: plug-in units often evaporate it in a tray using heat from the refrigeration system, while remote line-ups usually need a floor drain with a trap. In monsoon months the volume of water rises, so check trays and drains are sized for your climate rather than for a dry, air-conditioned test room.
Questions to ask before you buy
- At what room temperature and humidity was the product temperature rating tested?
- Is the unit plug-in or remote, and how much heat does a plug-in model release into the store?
- Are night blinds included, and can doors be retrofitted later?
- How is defrost water handled, and does the site need a drain?
- Who services the refrigeration system locally, and how fast is the response?
Planning a line-up
Multidecks come in modules that join into continuous runs with end panels. Plan the run length around category space, then check the electrical supply, drainage for defrost water, and — for remote systems — the route and length of refrigerant piping to the condensing unit. Ask who will maintain the system and how quickly they can reach the store, because a failed line-up is a large share of a store's chilled stock.
Frequently asked questions
- Why does the aisle in front of the multideck feel cold?
- Some cold air from the curtain always spills out. A very cold aisle can mean the curtain is disturbed or the shelves are overloaded, which also means the cabinet is working harder than it should.
- Can I use an open multideck in a non-AC shop?
- It is usually a poor choice. Without air-conditioning, heat and humidity overwhelm the air curtain. A glass-door merchandiser is far better suited to a non-AC store.
