A restoration technician in a hooded suit and respirator vacuuming a stripped commercial interior under containment sheeting, with two air movers, a dehumidifier, an air scrubber, and a moisture meter staged on the floor.

Structural drying

LGR vs Conventional Dehumidifier

Do I need an LGR dehumidifier, or will a conventional refrigerant unit dry this?

The short answer

Both remove water by condensing it on a cold coil. An LGR adds a pre-cooling stage, so it keeps pulling water at low vapor pressures where a conventional unit stalls. Conventional units are effective early, in warm and wet conditions. The LGR earns its cost in the tail of the dry-down and on dense materials.

LGR

Low grain refrigerant. Pre-cools incoming air before the evaporator, so it keeps condensing at low specific humidity.

Conventional

Standard refrigerant. Condenses on a single cold coil, with output falling as the air it is fed gets drier.

LGR compared with Conventional
CriterionLGRConventional
How it worksPre-cool stage plus evaporatorSingle evaporator coil
Low humidity outputContinues at low grainFalls off sharply as air dries
Best phase of the jobMiddle and tail of the dry-downEarly, while the load is wet
Class 3 and 4 assembliesGenerally requiredUsually insufficient alone
Purchase and rental costHigherLower
Weight and handlingHeavierLighter
VerificationGrain depression across the unitGrain depression across the unit

Which one this job needs

LGR

When the LGR is the right call

  • The job has moved past bulk water and the environment is already at moderate humidity, which is exactly where conventional output collapses.
  • Bound water in hardwood, plaster, or a low-permeance assembly is what is left, and drying has to continue at low vapor pressure.
  • The class of intrusion is 3 or 4, so the evaporation load and the material density both argue for a unit that will not stall.
  • The drying goal is aggressive relative to ambient conditions and the schedule leaves no room for a plateau.
Conventional

When conventional is enough

  • The affected area is warm and genuinely wet, where a conventional unit is working in the part of the curve it is good at.
  • The assembly is light and permeable and the class of intrusion is low, so the water is free rather than bound.
  • You are supplementing an LGR fleet during the wet phase rather than replacing it, which is a common and correct mixed deployment.
  • Cost or weight is the binding constraint on a job where the drying goal is modest and readings confirm progress.

What the standard actually says

S500 does not name a product class as mandatory. It sets the obligation to establish a drying goal and to verify progress with psychrometric readings, which is what actually decides this. The honest test is not the badge on the unit but grain depression across it and moisture content trending toward goal. A conventional unit holding depression is working; an LGR that has plateaued is not.

Sources

Stampede is a distributor, not a restoration contractor. The restoration contractor makes the final determination.

We stock both sides

Browse the categories these choices come from, or send a list and a rep will price it. If a maker we carry builds something not published on this site, ask for it by part number: that is a publishing gap, not a supply gap.

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Common questions

What does LGR actually stand for?

Low grain refrigerant. Grain refers to grains of moisture per pound of dry air, the unit specific humidity is measured in. The name describes the condition the unit is built to keep working in: air that is already low in moisture, where a conventional refrigerant dehumidifier loses most of its output.

Can I run LGR and conventional dehumidifiers on the same job?

Yes, and it is common. Conventional units carry the wet early phase efficiently while LGR units take the job through the tail. What matters is that each unit is verified by grain depression across it, so a stalled machine is identified and moved rather than left running as decoration.

How do I know the dehumidifier is actually working?

Measure specific humidity at the intake and at the outlet and compare. That difference, the grain depression, is the direct evidence water is being removed. A unit running with little or no depression is either in an environment approaching drying goal or has a fault, and both need a decision rather than another day of runtime.

Keep reading

Desiccant vs LGRWater damage drying calculatorWater damage restoration supplyAll comparisons