Sizing an LGR dehumidifier is not guesswork but a load calculation. In restoration, houses, warehouses, or crawlspaces, you size based on moisture load, not just square footage. Professional restoration companies are very familiar with this kind of calculation. This article is mainly intended to help people in need of dehumidification service understand why their service providers make such a “big fuss”.

 

1. Understand What You’re Sizing For

An LGR dehumidifier is rated in:

PPD (Pints Per Day) at AHAM conditions (80°F / 60% RH)

Airflow (CFM)

Operating grain depression capability

 

In water damage and commercial drying, we calculate based on:

Room volume

Desired humidity reduction

Initial humidity

Air exchanges and infiltration

Material moisture load

 

2. Quick Rule-of-Thumb Sizing

In water damage restoration, common industry guidance:

1 LGR per 1,000–1,500 sq ft (standard 8 ft ceilings)

OR

1 LGR per 10,000–15,000 cubic feet

This assumes moderate saturation.

For severe water intrusion → reduce coverage area by 30–50%.

 

3. Engineering Method of Sizing LGR Dehumidifiers

For more precision:

Step 1: Calculate Room Volume

Volume = Length × Width × Height

Step 2: Calculate Initial Grains Per Pound (GPP)

Use psychrometrics.

Example:

85°F / 75% RH ≈ 125 GPP

Target 50% RH at 75°F ≈ 65 GPP

Grain difference:

125 - 65 = 60 grains

Step 3: Calculate Moisture Load in Grains

Total grains = Volume × Grain difference

Convert grains to pounds:

7,000 grains = 1 pound of water

Convert pounds to pints:

1 pound ≈ 1 pint

 

4. Example Calculation of LGR Dehumidifiers

Scenario: Warehouse, 2,000 sq ft, 10 ft ceiling.

Initial: 85°F / 75% RH

Target: 75°F / 50% RH

 

Step 1: Volume

2,000 × 10 = 20,000 cubic feet

Step 2: Grain Difference

125 GPP − 65 GPP = 60 grains

 

Step 3: Total Moisture Load

20,000 × 60 = 1,200,000 grains

Convert:

1,200,000 ÷ 7,000 = 171 pounds ≈ 171 pints

Result:

You must remove 171 pints of water to reach the target condition (ignoring ongoing infiltration).

Recommended Preair dehumidifier:

No.	LGR165L
Dehumidification capacity	165PPD (80°F / 60% RH)
Drainage method	Water pump
Drainage pipe length	6M
Operating temperature range	41℉-100.4℉
Operating humidity range	20%RH-90%RH
Size For	3,500 to 7,000 square feet
Wifi Capable	Yes
Air volume	515CFM
Wind speed control	Dual speed automatic
Refrigerant	R32

 

5. Real-World Adjustment Factors

Increase the flood dehumidifier, if:

Active water intrusion

Concrete slab moisture emission

High outside humidity

Air leakage

Wet structural materials

Large open doors

Grow rooms with transpiration load

 

Reduce coverage if:

Low ceiling height

Well-sealed space

Minimal moisture source

 

Preair is a professional manufacturer of commercial dehumidifiers. The LGR dehumidifier is specifically designed for water damage restoration. It has a compact design, high efficiency, and a long warranty. The components of our dehumidifier include high-quality copper tubes, compressors, evaporators, and condensers. Furthermore, the fan and water pump are also durable. Preair LGR dehumidifiers have been sold worldwide and recommended by professional restoration companies.