What are the main advantages of using dehumidifiers in cold storage?

The dehumidifier removes incoming moisture before it reaches the evaporator. This reduces ice build-up and defrost demand on the evaporator and preserves cooling efficiency. Fog, ceiling dripping and frost on floors and products are prevented, protecting both product quality and workplace safety. Stable humidity also limits product weight loss.

At what temperature range is humidity control needed in cold storage?

What matters is not the room temperature but the dew point of the required condition. In any store with a dew point below +5 °C, humidity is controlled with a silica gel rotor, because a condensing unit's coil ices up. For example, +2 °C / 90% RH has a dew point of +0.5 °C and 4 °C / 85% RH +1.7 °C. TFT ADI/ADO units suit freezer rooms (−30…−18 °C); the AD series suits 0…+10 °C cold rooms and loading docks. Condensing units (CD/CDNP, operating range +10…+40 °C) are economical only in cool rooms above 15 °C with dew points above +10 °C.

How much moisture load does humid air entering through a cold storage door create?

The moisture entering depends on the door size, how long it stays open and the temperature–humidity difference across it. Using the ASHRAE Gosney–Olama method, a 3 m × 3 m door between 32 °C / 60% RH outdoor air and a −20 °C freezer admits about 5 kg of water vapour per 45-second opening without a strip or air curtain; at 8 openings per hour that is about 40 kg/h. With a dry anteroom in front of the door held at 5 °C and about −4 °C dew point, the moisture per opening falls to about 0.4 kg. Drying the anteroom is therefore the most effective measure; the remaining load is handled by the dehumidifier.

I already have a cooling system in my cold storage; why do I need a separate dehumidifier?

The refrigeration system lowers the temperature and in the process holds some moisture as ice on the evaporator; but its purpose is temperature control, not dehumidification. Ice on the evaporator reduces efficiency and returns to the room during defrost. In stores with a dew point below +5 °C, a condensing dehumidifier would also ice up. TFT silica gel rotor dehumidifiers complement the refrigeration system; according to the product pages, the AD 1000-3100, AD 3000-6500 and ADP series operate at −30…+40 °C and the ADI/ADO freezer-room series at −30…−18 °C.

Which system is recommended for a deep freezer operating at −30°C?

A silica gel rotor dehumidifier is required for −30 °C applications; a condensing unit cannot operate at this temperature. The TFT ADI/ADO 1500-4500 series, developed for freezer rooms, operates at −30…−18 °C, with a capacity of 29.8–92.2 kg/24 h at −18 °C / 100% RH process inlet. ADI is installed inside the room, ADO outside. Door opening frequency, anteroom conditions and seasonality must be taken into account when sizing.

What should the dehumidifier maintenance schedule look like?

NKT's recommended maintenance plan: for TFT silica gel rotor units, regular filter checks and replacement, periodic general inspection (rotor, fans, regeneration heater) and an annual comprehensive service (rotor surface, sensor calibration). With proper filtration the rotor lasts about 10 years. Condensing units additionally need an annual compressor and refrigerant check. In dirty or dusty environments the filter check interval should be shortened.

Can a dehumidifier be retrofitted to my existing cold storage?

Yes, a dehumidifier can be retrofitted to an existing cold store. An internally mounted unit (TFT ADI type) requires the least intervention; only the regeneration line is routed outside. An externally mounted unit (TFT ADO type) needs duct connections but adds no heat load to the room and is easy to service. NKT supports the selection of the right TFT model and mounting type based on room volume, temperature, door traffic and existing refrigeration capacity.

Does the dehumidifier's energy consumption increase cooling costs?

A dehumidifier consumes energy and releases heat to the room: about 0.7 kWh of latent heat is converted to sensible heat for every kilogram of water removed, and a silica gel rotor unit adds the heat carried over from regeneration. This heat must be added to the refrigeration load. On the other hand, ice build-up on the evaporator and defrost demand decrease. The net energy balance is evaluated per project, depending on door traffic, anteroom conditions and defrost method.

How is the dehumidifier integrated with the cooling system?

The TFT Italy dehumidifier's supply duct is directed to the evaporator intake. Dry warm air from the unit passes over the evaporator, gets cooled and returns to the room dry. Integration with standard control units enables centralised management of both cooling and humidity functions; setpoint conflicts are prevented.

How does a dehumidifier reduce product weight loss (shrinkage)?

In cold storage, fresh produce, meat and dairy lose weight through surface evaporation; the closer the room RH is to the product's equilibrium moisture, the lower the loss. By holding the dew point steady, the dehumidifier prevents fluctuations and helps keep the target condition stable (e.g. 85–90% RH at +4 °C, dew point +1.7…+2.5 °C). Ceiling dripping after defrost is prevented by the same dew-point control.

Technical Article28 min read

Dehumidifier Use in Cold Storage Rooms

Why moisture turns into ice in cold and frozen stores, at which dew point a condensing unit ices up, and how to select a silica gel rotor dehumidifier: door load, anteroom drying and refrigeration integration.

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Related Glossary Terms

For deeper definitions of the technical concepts in this article, browse the related entries in the NKT Glossary:

Relative Humidity (RH)Absolute Humidity Moisture Load Dew Point Psychrometric Chart Dry Bulb Temperature Sensible Heat Latent Heat Silica Gel Rotor (Desiccant Rotor)Reactivation (Regeneration)Defrost ASHRAE (American Society of Heating, Refrigerating and AC Engineers)ACH (Air Changes per Hour)Hygroscopic (Moisture-Attracting)Sorption (Adsorption + Absorption)Humidification Capacity (kg/h)Hygroscopic Material Silica (SiO₂)Condensate (Steam Condensation)

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Dehumidifier Use in Cold Storage Rooms

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