Sheet 08 · Surface heat
Ice at freezer doors and ramps
Subfloor heat protects the ground. It does nothing for the ice that forms on the floor surface at a freezer door. That needs its own heat, at the surface.
01Why ice forms at the door
Each time the door opens, warm, humid air from the dock or corridor flows in along the floor. It meets a floor that is below freezing, and its moisture condenses and freezes on the surface. Traffic tracks in more water. The result is a sheet of ice at the threshold and on ramps: a slip hazard for people and a braking and steering hazard for lift trucks.
Reducing infiltration with strip curtains, air curtains, fast-acting doors and vestibules reduces the load. Where ice still forms, the surface around the opening is heated just enough to stay above freezing.
02Surface heating methods
| Method | Where it fits |
|---|---|
| Heating mats | Cable pre-spaced on a mesh or adhesive carrier, rolled out and embedded in a topping or mortar bed. Fast to install over a defined area such as a threshold. |
| Heating cable in the slab | Cable fastened to reinforcing and cast into the slab or ramp, for larger or irregular areas. |
| Door frame and threshold heaters | Supplied with many freezer doors to keep seals and sills free of ice. Coordinate with the door manufacturer. |
Surface heat sits above the insulation, close to the wearing surface, and must stay within the doorway zone. It is controlled and circuited separately from the subfloor frost heave system, and its heat load is counted in the refrigeration load.
03Control and protection
- Control from a slab sensor near the threshold, with or without a moisture sensor, so the surface is heated only when ice can form.
- Surface heating circuits can be added to the freezer floor control panel, with their own breakers, ground-fault protection and alarms.
- Ground-fault equipment protection is required on each circuit.
- Single-connection mats do not have a separate end-of-run point, so circuit monitoring is by current and ground-fault status rather than end-of-run relays.
Heating mat manufacturer data sheet (PDF, reference). Confirm current models and ratings with the manufacturer.