Rated vs measured dehumidifier capacity on a restoration job

What does rated dehumidifier capacity mean?

A restoration dehumidifier's rated capacity applies at its stated test conditions: the current Dri-Eaz 6000Li lists 100 pints per day at 80°F and 60% RH, compared with 219 pints per day at 90°F and 90% RH. Measure site capacity by collecting condensate over a timed interval, then cross-check it against inlet and outlet humidity ratio and actual airflow. Grain depression measures water removed per pound of dry air; airflow and operating time determine how much water leaves the job. Sources: Legend Brands specifications and ASHRAE Fundamentals 2021.

Capacity is a rate, rather than reservoir size or a promised completion date. The structural drying field guide covers extraction and material goals; this worksheet measures equipment removal.

AHAM, saturation and DOE numbers use different entering air

Restoration product sheets commonly label 80°F/60% RH capacity as AHAM. DOE's current consumer test procedure, 10 CFR part 430, Appendix X1, incorporates AHAM DH-1-2022 and specifies 65°F/60% RH for portable units and 73°F/60% RH for whole-home units. Retain the condition printed beside each restoration rating.

The selected manufacturer's saturation label means 90°F/90% RH, even though saturation itself means 100% RH. ENERGY STAR explains the consumer rating change from warmer to cooler portable-unit testing, while DOE's consumer-dehumidifier program identifies the regulated product category. Use actual-condition evidence to establish LGR site capacity.

Photograph the nameplate and retain the matching model, electrical market, refrigerant and revision. Keep the IICRC restoration framework separate from model-specific OEM performance claims.

Which manufacturer specifications should you compare?

Compare equal-condition removal first, then airflow, electrical supply and permitted inlet temperature. Installed ducts, filter condition and fan mode determine actual flow. Table B preserves each source's configuration.

Phoenix's DryMAX XL manual TS-1141, June 2023 Rev. E, lists 225 CFM in Quiet Mode versus 300 CFM maximum. Record that mode with every capacity check. Reducing published airflow to 75% does not establish a 75% water-removal rate because the moisture reduction per pound also changes. DryMAX XL manual, section 3.3.14.

The DryMAX XL documents disagree on their upper operating temperature: the posted specification sheet gives 110°F, while TS-1141 Rev. E gives 104°F. Use the instructions matching the actual serial number; a unit governed by that Rev. E manual has a 104°F upper limit. Obtain the OEM document resolving the discrepancy before extending that unit's operation to 110°F. Posted DryMAX XL specification.

The US Phoenix 250 MAX sheet's separate 31-gallon/day maximum claim has no adjacent test condition. Use its explicit AHAM value for equal-condition comparisons and retain the US electrical configuration. 250 MAX US specification.

Which psychrometric readings belong in the capacity record?

Measure entering and leaving temperature and RH at the machine, together and in the same operating mode. Record chamber, outdoor and unaffected-area readings separately. Keep warm discharge and air-mover jets from contaminating the inlet sample.

Use humidity ratio in grains per pound of dry air, often abbreviated GPP, to compare moisture content. ASHRAE Handbook Fundamentals 2021, chapter 1 distinguishes humidity ratio from specific humidity, whose denominator includes water vapor, and from mass-per-volume quantities. The psychrometric chart guide explains the chart; Table C gives the properties needed here.

Method: Table C contains Anvilfield estimates using ASHRAE Fundamentals 2021, chapter 1, equations (5), (21) and (28): IAPWS-IF97 saturation pressure over liquid water, humidity ratio and specific volume, with all states at 101.325 kPa. Inputs are the named published test conditions or selected worksheet states. Calculations retain unrounded properties; displayed values use two decimals. NIST SP 811, 2008, Appendix B.8 supplies unit conversions.

Keep temperature, humidity and pressure together

Heating air lowers its relative humidity at unchanged humidity ratio. Therefore a hot, low-RH outlet alone does not prove water removal. Dew point helps describe moisture state, while humidity and dew-point control explains how that state affects equipment operation.

How do you calculate grain depression?

Subtract outlet humidity ratio from inlet humidity ratio. Anvilfield estimates 25.75 grains per pound of dry air from the unrounded worked states; the displayed inlet and outlet values are 92.10 and 66.36 GPP. A positive difference means moisture loss across simultaneous machine readings; morning-to-afternoon chamber GPP describes a chamber trend.

Why a larger grain depression can remove the same water

Anvilfield estimates that 300 actual CFM with a 15-grain depression removes the same 64.07 pints per day as 150 actual CFM with a 30-grain depression at an 80°F, 60% RH inlet and standard atmospheric pressure. Table D uses continuous steady operation and Appendix X1's rounded 1.04 lb/US pint convention.

Judge a grain difference alongside actual flow, collected water and material progress. A grain threshold alone cannot establish adequate drying or justify an equipment day: the same depression produces different removal rates at different airflows. A small difference also makes probe uncertainty a larger fraction of the result; establish whether the difference is resolved before diagnosing the machine.

How do CFM and grains become water-removal capacity?

Divide actual volumetric airflow by specific volume to obtain dry-air mass flow, then multiply by the water lost per pound of dry air. Integrate that water-removal rate over operating time. Pounds per hour is the primary mass result; convert it to pints or liters after the mass balance.

Method box: one set of equations with units

Using ASHRAE Fundamentals 2021 and NIST SP 811 conversions, the worksheet uses the following equations. Q is actual airflow in ft³/min; v is specific volume in ft³/lb dry air at the airflow measurement plane. Both mass-flow rates are in lb/h; GD is in grains/lb dry air.

NIST defines the unit conversions; the 1.04 lb per US liquid pint of water is the deliberately rounded density convention used in DOE Appendix X1. A pint is a volume, a pound is a mass, and an Imperial pint is a different volume. Retain the US basis in exported records.

Actual flow, standard flow and altitude

Anvilfield estimates that 260 actual inlet CFM at 80°F/60% RH and 101.325 kPa represents 1,122.86 lb dry air/h. Substituting the 6000Li's 320-CFM published maximum would overstate that mass flow and the resulting removal estimate by 23.08%.

Measure the whole stream using a suitable flow hood or a velocity traverse across a documented duct area, following the instrument instructions. One centerline velocity multiplied by gross grille area misses the velocity profile and grille obstruction. Record adapters and their restriction, ducts, filter and fan mode; if only nominal flow is available, label the air-side result a nominal-flow estimate and establish field removal by collection.

Pair outlet-measured actual CFM with outlet specific volume. In Anvilfield's worked pair, conserved dry-air mass converts 260 inlet CFM to 270.47 outlet CFM as the air warms to 105°F/20% RH. Standard CFM instead carries an instrument-defined reference density; retain that basis before converting to dry-air mass.

Calculate both humidity ratios and specific volume at local station pressure, not weather-service sea-level-corrected pressure. Phoenix limits DryMAX XL use to elevations no higher than 2,000 m (6,562 ft.) in TS-1141, June 2023 Rev. E, and TS-2026, November 2023 Rev. E; a pressure correction does not extend that operating limit. Phoenix safety instructions. Pressure changes the moisture difference per pound and the pounds processed per CFM, while refrigeration performance needs its own actual-condition data. For installed building-duct losses, the duct leakage guide addresses the surrounding distribution system; document portable-unit connections separately.

How do you measure condensate without pump-cycle errors?

Capture the complete discharge from one identified refrigerant unit in a tared container and weigh it over a recorded interval. Prevent overflow, identify the drain source and exclude extractor water, HVAC condensate and other machines. Photograph the collection setup. Phoenix TS-1141, June 2023 Rev. E, requires GFI protection in wet areas and prohibits operation with the top cover removed. Collect at the external hose; keep the operating enclosure closed. DryMAX XL manual, sections 3.2 and 5.

Anvilfield's field worksheet uses a two-hour collection after stabilization plus a 24-hour operating summary. Extend or shorten collection to resolve enough water on the scale and capture multiple pump cycles. DOE Appendix X1 defines a separate laboratory certification procedure.

Account for water held in the machine

A timed condensate balance counts collected water plus any increase in water stored in the machine and hose, so unequal reservoir states can distort a short field capacity test. Include liquid water and ice held on the coil, basin water and the discharge hose; capture purge water and record startup, defrost and shutdown transitions. With no spills or leaks, the balance is: M_net = M_collected + (M_stored,end − M_stored,start).

Anvilfield estimates that 8.20 lb collected over two hours with a 0.60 lb increase in stored water represents 8.80 lb net removal, equivalent to 101.54 pints/day of continuous operation. With equal storage, the same collection gives 94.62 pints/day. Apply a storage correction only when the change is established; matching reservoir levels alone leaves coil and hose storage unresolved.

Previously retained water can increase collected discharge, while coil water re-evaporating into the room reduces net removal. When storage cannot be quantified, extend collection through complete operating and defrost cycles with comparable start and end states. A longer interval reduces the relative effect of retained water; it does not measure the remaining storage difference. Phoenix's TS-1141, June 2023 Rev. E specifies a default three-minute shutdown followed by a 20-second final purge; capture that discharge when it falls within the test boundary.

What agreement is good enough?

Compare matching intervals using scale, probe and airflow uncertainty. Vaisala's measurement-performance article, published 2022 and updated 2026 explains why accuracy, repeatability, hysteresis and stability describe different aspects of measurement. Co-locating probes exposes relative bias; retain calibration information to address absolute accuracy.

Anvilfield's sensitivity calculation applies an assumed ±5-grain difference error and ±10% airflow error to the worked 95.31-pint/day air-side result. Multiplying the low and high bounds gives 69.12 to 125.20 pints/day. Those are selected sensitivity bounds, rather than instrument specifications, an acceptance tolerance or a statistical confidence interval.

An assumed ±2 RH percentage-point error at each worked air state permits grain depression from 15.87 to 35.61 grains/lb with temperature and airflow held exact. At the hotter outlet, the same RH error has a different GPP effect. Recalculate using instrument specifications at each operating state, including temperature error. After moving a probe, wait for both temperature and RH readings to settle before pairing the values.

Worked example: reconcile air-side capacity with collected water

Using ASHRAE's 2021 psychrometric equations, Anvilfield estimates that 260 actual inlet CFM at 80°F and 60% RH, leaving at 105°F and 20% RH at 101.325 kPa, removes 4.13 pounds of water per hour, equivalent to 95.31 pints per day of continuous operation. The matching collection worksheet uses 8.20 lb over two hours with equal stored-water states, giving 4.10 lb/h.

Method: Anvilfield estimates combine the selected inputs in Table E with the 6000Li specification checked November 5, 2026, and ASHRAE Fundamentals 2021 equations (5), (21) and (28). Carry unrounded air properties through the mass balance, apply Appendix X1's 1.04 lb per US pint convention, then round results to two decimals. Subtracting already rounded table states can change the final hundredth.

The 0.73% arithmetic difference is smaller than the worked sensitivity bounds; retain raw inputs and instrument uncertainty. When methods disagree, first reconcile collection boundaries and stored water, then probe placement and airflow; compare the same operating interval before assigning a refrigeration fault.

At that collection-based rate, 20 hours of active removal produces 78.85 pints in an elapsed day when the remaining four hours contribute zero net removal. A compressor-hour counter alone does not establish those conditions. For cycling and defrost, sum interval water masses including re-evaporation, or collect throughout the full elapsed day; average the interval mass-removal products rather than separately averaged flow and grain depression.

How should capacity be trended as the job dries?

Trend corrected water-removal rate alongside inlet GPP, operating states and marked material readings. Falling collection with falling material moisture can reflect a declining available load. Falling output while the same assembly remains wet calls for a check of delivery, access, infiltration and equipment operation.

Published condition change versus a site trend

Anvilfield estimates a 10.81% removal reduction between the Santa Fe Rx Rev. 10/16/17 sheet's two test states. Apply that percentage to this named-model comparison only.

Table G contains Anvilfield estimates at 101.325 kPa using selected interval inputs and the water-removal balance. The first row uses air-side removal; Table E also shows the collection-based result. The three calculated intervals total 145.06 pints, about 68.64 L.

Measured capacity trend: the reusable job record

Fill the site record with timestamps, raw readings and actual collection masses. Plot each interval's corrected lb/h against its midpoint time, with inlet GPP and material readings on separately labeled panels. Retain scale records, probe IDs and storage corrections with the trend.

Anvilfield's monitoring schedule takes a stabilized baseline, repeats after equipment moves or duct/settings changes, and compares results at least once per 24 hours during active drying. Log operating states more frequently where controls permit. The Phoenix quick-start guide TS-2026, November 2023 Rev. E distinguishes standby, startup and dehumidifying indications; preserve those states instead of treating every powered hour as an hour at full removal.

How much heat and electricity does the unit add?

At the current Dri-Eaz 6000Li's published 748-watt input, Anvilfield estimates 17.95 kWh for 24 continuous operating hours. Meter actual kWh for the job; multiplying volts by amps establishes apparent power rather than real watts for an AC motor load.

Table H multiplies constant published watts by elapsed hours and divides by 1,000. For electricity cost, multiply metered kWh by the job tariff and include applicable demand charges. Track air movers and supplemental heat separately; equipment rental and monitoring labor follow the contract.

Separate outlet heating from whole-chamber energy

Anvilfield estimates that condensing the worked 4.13 lb/h converts about 4,378 Btu/h of latent energy to sensible heat, using approximately 1,060 Btu/lb near a 60°F condensation temperature. Adding the 748 W electrical reference, about 2,552 Btu/h, gives roughly 6,900 Btu/h of sensible heating across the unit. Actual condensation temperature, liquid discharge and casing heat transfer alter that estimate.

The latent heat released during condensation came from the moisture and evaporation process. For the whole closed chamber, electrical input is added energy; condensation redistributes energy already inside that boundary. Use enthalpy for total moist-air energy and keep water discharge or reactivation exhaust crossing the boundary in the accounting.

The worked collection rate and continuous 748 W input calculate to 2.49 L per operating kWh. DOE Appendix X1's integrated energy factor uses its prescribed operating and low-power-mode accounting. Label the worksheet result water per operating kWh, and use logged cycling and energy for an actual daily comparison.

When do temperature and technology change the answer?

Use the actual unit's inlet operating range and condition-performance data together. Permitted operation does not guarantee AHAM output. The worked 105°F outlet is a leaving-air condition; compare the manufacturer's inlet limit with entering air.

Phoenix's January 30, 2020 desiccant application article recommends desiccants below 65°F, while its DryMAX XL TS-1141 Rev. E manual permits refrigerant-unit operation down to 33°F. Treat the first as an application recommendation. Compare actual output, defrost behavior, power and the needed drying environment within the matching unit's operating envelope.

Legend Brands' June 23, 2025 LGR performance article identifies 80°F/20% RH and 70°F/30% RH as low-grain test states. Anvilfield estimates 30.27 and 32.53 GPP at standard atmospheric pressure. Use material goals and effective removal for the equipment decision.

A desiccant needs an exhaust balance

The Phoenix D385 specification, part 4026700 lists 385 CFM process air, 75 CFM reactivation air and 130 pints/day equivalent removal at 80°F/60% RH. Measure process dry-air mass and humidity-ratio reduction, then trace the wet reactivation exhaust.

Reactivation drawn from the chamber creates replacement-air demand. A four-hole arrangement can take reactivation intake and discharge outside while recirculating process air; choose routing consistent with contamination control and the intended pressure arrangement. The desiccant systems guide develops those system choices.

Apply a single conserved-dry-air process balance only across a boundary where that conservation holds. Wheel-seal leakage, purge and cross-stream mixing require separate entering and leaving mass-flow accounting. Record reactivation inlet state, available heater power and exhaust restrictions because process inlet temperature/RH alone cannot define desiccant output.

Is falling output a machine fault or a drying-system problem?

Read the material map before adding equipment. A dehumidifier can remove water normally while inaccessible moisture stays beneath flooring, or while outdoor replacement air supplies much of the collected water. Use Table I to separate causes.

Quantify the replacement-air load before blaming the machine

Anvilfield estimates that 100 actual CFM of incoming air at 90°F/60% RH, replacing equal dry-air mass exhausted from an 80°F/60% RH chamber at 101.325 kPa, adds 49.63 pints/day of water vapor. Incoming air is 127.89 GPP with specific volume 14.26 ft³/lb dry air. The calculation divides incoming flow by its own specific volume and applies the unrounded 35.79-grain excess.

Against the selected 94.62-pint/day machine rate, that replacement load leaves about 45 pints/day for material evaporation and other internal sources at unchanged chamber vapor storage. A full collection container can therefore coexist with slow structural drying. Include an exhaust fan or chamber-fed reactivation stream in the same makeup-air balance.

Compare incoming and exhausted dry-air mass and GPP when assessing ventilation. The chamber balance includes material evaporation, replacement air and internal vapor sources against dehumidifiers, HVAC condensate and net vapor exhaust.

For recurring basement entry, inspect drainage and sump-pump protection as part of the source check.

What proves equipment use, drying progress and invoice scope?

Keep serial numbers, paired air states, airflow basis, collection boundaries, power, operating states and marked material readings together. Separate days installed, powered hours and compressor hours. Record why equipment was added, moved, reduced or removed, with the timestamp and material evidence supporting the decision.

IICRC identifies psychrometry, equipment and project documentation within ANSI/IICRC S500, fifth edition (2021). Model limits come from matching manuals. Connect equipment actions with material goals; slab moisture testing for flooring addresses a separate assembly-acceptance task that air readings cannot replace.

Estimate the scope without promising a fixed drying duration

Separate extraction, access or removal, air movement, dehumidifier days, monitoring labor, power, final material verification and rebuild in the estimate. Rated pints/day cannot turn building volume into a completion date: remaining material water, access and evaporation rate control the load reaching the machine. Public-facility estimators use PorchRocket Bid Control to find restoration and cleaning solicitations and review past awards when planning equipment and monitoring scope.

How many dehumidifiers does the site load require?

Divide documented daily vapor-removal load by expected daily site removal per unit, including availability, and round upward. Anvilfield estimates that a selected 180-pint/day load requires three units at the worked 78.85-pint/day site yield: two supply 157.69 pints/day and three supply 236.54. Dividing only by the 100-pint rating would select two under these inputs.

Establish load from chamber conditions, ventilation and source loads, and material response; use the applicable project method for initial selection. At stable chamber humidity, total measured removal approximates the continuing vapor load. If chamber humidity rises, removal is falling behind; falling humidity means removal also draws down stored airborne moisture. Re-measure after changing the setup because additional units compete for declining moisture, add heat and use available circuits.

Capacity records explain equipment quantity and days. Contract scope, authorization and payment terms govern billing; a positive grain difference or a rating percentage alone cannot establish reimbursement. Retain the parent structural drying log with final material verification so the invoice and completion decision refer to the same job history.

Field checklist: a repeatable capacity check

Use this Anvilfield workflow at baseline and after setup changes; retain the resulting record.

• ☐ Identify model, serial number, voltage market, refrigerant and matching manual; retain capacity and rating conditions.
• ☐ Confirm source control, electrical access and contamination scope support the measurement and drying arrangement.
• ☐ Check entering temperature against the matching manual; record humidistat, fan and defrost state.
• ☐ Inspect filter, coil airflow path, clearances and ducts; correct restrictions before the baseline.
• ☐ Record station pressure or elevation and instrument IDs; co-locate probes to identify relative bias.
• ☐ Measure stabilized inlet/outlet temperature and RH together; calculate humidity ratios and grain depression.
• ☐ Measure installed actual airflow at a documented plane; use specific volume at that plane.
• ☐ Tare the container, identify the single discharge, record stored-water state and start time.
• ☐ Capture pump cycles and purge water safely; record end time, water mass, end storage and downtime.
• ☐ Calculate air-side and collection lb/h, continuous equivalent and actual interval removal; investigate differences beyond measurement uncertainty.
• ☐ Record chamber, outdoor and unaffected states plus marked material readings; identify infiltration and inaccessible moisture.
• ☐ Record the resulting equipment or scope change, reason and next reading time; verify material goals before equipment removal.

Have the field lead tie each equipment decision to the marked material readings and project drying goals. Record the measurement scale and depth so the next visit compares the same material condition.

Reusable evidence: psychrometric states, water-removal balance, worked capacity, capacity trend and measured-capacity record.

Reviewed 2026-11-05. Update log: rechecked all listed sources; aligned calculations with the cited ASHRAE equations; clarified altitude limits, defrost storage and interval comparisons.

How to cite this page: Anvilfield, Rated vs measured dehumidifier capacity on a restoration job, 2026, https://anvilfield.com/field-guides/plumbing/restoration-dehumidifier-capacity-field-performance/.

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Sources checked

• S1. Legend Brands, current LGR 6000Li product specification, R32 configuration. Current R32 configuration, option 103614; rating states, power, airflow and inlet limits. Web specification checked 2026-11-05.
• S2. Phoenix DryMAX XL owner's manual, TS-1141, 06/23 Rev. E. TS-1141, 06/23 Rev. E. Model capacity, Quiet Mode, inlet limits, pump/purge operation and diagnostics. Checked 2026-11-05.
• S3. ASHRAE Handbook Fundamentals 2021, chapter 1, Psychrometrics, public SI chapter. 2021 Fundamentals, chapter 1, equations (5), (21) and (28): IAPWS-IF97 saturation pressure, humidity ratio and specific volume. Equations and calculated states rechecked 2026-11-05.
• S4. DOE, 10 CFR part 430, subpart B, Appendix X1, current text as checked, hosted by Cornell LII. Current primary legal text via Cornell LII: DH-1-2022 incorporation, consumer test states and water-density convention. Checked 2026-11-05.
• S5. US EPA ENERGY STAR, Dehumidifier Testing and Capacity, undated current public guidance. Consumer rating-condition change and capacity-label guidance. Checked 2026-11-05.
• S6. Phoenix DryMAX XL spec sheet, parts 4037000 and 4037060, no printed revision. Parts 4037000/4037060; no printed revision. Preserve the 110°F sheet versus 104°F Rev. E manual discrepancy. Checked 2026-11-05.
• S7. Phoenix 250 MAX US spec sheet, part 4030010, no printed revision. US part 4030010; no printed revision. Equal-condition removal, unducted airflow and operating envelope. Checked 2026-11-05.
• S8. Phoenix D385 spec sheet, part 4026700, no printed revision. Part 4026700; no printed revision. Process/reactivation airflow, equivalent removal and two-circuit supply. Checked 2026-11-05.
• S9. NIST SP 811, 2008 edition, Appendix B.8, current online presentation. 2008 edition, Appendix B.8. Mass, volume and energy unit conversions. Checked 2026-11-05.
• S10. Legend Brands, The Secrets Behind the Best LGR Dehumidifiers, June 23, 2025. June 23, 2025. Manufacturer explanation of rating terminology and low-grain testing. Checked 2026-11-05.
• S11. IICRC, S500 official publisher page, fifth edition (2021). Official publisher scope and fifth-edition (2021) identity; revision work underway. Checked 2026-11-05.
• S12. Phoenix, How to Dry Using Desiccant Technology, January 30, 2020. January 30, 2020. Desiccant application guidance, reactivation routing and replacement-air effects. Checked 2026-11-05.
• S13. Vaisala, Understanding Measurement Performance and Specifications, published January 4, 2022; page metadata modified January 16, 2026. Published January 4, 2022; modified January 16, 2026. Accuracy, repeatability, hysteresis and stability. Checked 2026-11-05.
• S14. Santa Fe Rx spec sheet, part 4030440, Rev. 10/16/17. Part 4030440, Rev. 10/16/17. Historical published minimum performance at two entering conditions. Checked 2026-11-05.
• S15. US DOE, Consumer Dehumidifiers, current public program page. Consumer-dehumidifier program scope and test-procedure references. Checked 2026-11-05.
• S16. Phoenix DryMAX XL, DryMAX BLE and DryMAX XL Pro quick-start guide, TS-2026, 11/23 Rev. E. TS-2026, 11/23 Rev. E. Startup and operating indications; altitude limit and operating safety instructions. Checked 2026-11-05.