LGR stands for low grain refrigerant. It is the dehumidifier technology that professional restorers rely on because it keeps removing water from air that is already fairly dry, which is exactly the situation on day two and three of a structural drying job. Every Thorair Pro dehumidifier is an LGR unit.
How an LGR dehumidifier works
A standard refrigerant dehumidifier draws warm, humid air over a cold evaporator coil. Water condenses on the coil, drains away, and the drier air is reheated and returned to the room. The catch is that once the room drops below about 40% relative humidity, the incoming air is no longer humid enough to condense much moisture on the coil, so removal falls away.
An LGR dehumidifier adds a heat exchange stage. Incoming air is pre-cooled by the cold, dry air leaving the evaporator before it reaches the coil. Because the air arrives at the coil already closer to its dew point, more water condenses out, even at low humidity. The result is a lower achievable grain depression (grains of moisture per pound of air), hence the name.
Why it matters on a restoration job
- Faster drying in the later stages. Conventional units stall as the air dries; LGR units keep pulling water out down to the target moisture content of the materials.
- Fewer machine days. Shorter jobs mean less equipment rental time and lower power use per loss.
- Meets restoration standards. Industry drying standards recommend LGR or desiccant units for Class 2 and Class 3 water losses.
- Better for wall cavities and subfloors. Bound water in timber, plaster and concrete only releases when the surrounding air is dry.
LGR versus desiccant dehumidifiers
| LGR (Thorair) | Desiccant | |
|---|---|---|
| Best temperature range | 15°C to 35°C, typical Australian conditions | Cold rooms and unheated spaces |
| Power use | Lower per litre removed | Higher, uses heaters to regenerate |
| Water handling | Pumped out through a hose | Vented as warm moist air, needs ducting outside |
| Typical use | Water damage, construction, warehouses, homes | Cold storage, deep drying of hardwood floors |
For the vast majority of Australian water damage and construction drying, an LGR unit is the more efficient choice. Desiccants earn their place in cold conditions or when very low humidity is needed for a specialist task.
The Thorair LGR range
The Pro LGR 50L packs LGR performance into a 32 kg stackable unit. The 70L adds a Panasonic compressor and 300 to 550 CFM of airflow for larger rooms. The Pro LGR 90L moves 600 CFM and removes up to 105 litres a day under test conditions. All three use R410A refrigerant, which contains no ozone-depleting chlorine, and are SAA and ASA certified. Compare them on the commercial dehumidifiers page.
Frequently asked questions
What is a grain of moisture?
A grain is 1/7000th of a pound. Grains per pound (GPP) is the amount of water vapour in a pound of dry air. Restorers use GPP rather than relative humidity because it does not change with temperature, making it a better measure of how much water is actually in the air.
Does LGR use more electricity?
No. Because the heat exchange stage is passive, an LGR unit removes more water for the same compressor power, so the energy used per litre removed is lower than a conventional refrigerant unit.
Is R410A refrigerant environmentally safe?
R410A is a hydrofluorocarbon blend that replaced R22. It contains no chlorine and does not deplete the ozone layer, and it operates at higher pressure which improves efficiency.
Can I use an LGR dehumidifier in a cold room?
Thorair units include thermostat defrost control so they can operate in cool conditions, but below about 10°C a desiccant unit will outperform any refrigerant dehumidifier.
