Field-Effective Dehumidifier Capacity at Chamber Grain Depression
Derates a nameplate AHAM pint rating to its field output as the chamber dries and the inlet grains fall.
Example
You enter
- Nameplate AHAM rating (pints/day) 130
- Derate factor (0-1, off the unit's curve) 0.5
- Required removal (pints/day) 300
You get
- Field-effective output per unit 65 pints/day
- Units by field output (honest) 5 unit(s)
- Shortfall the nameplate hides 2
Checked against published worked examples from: Restoration & Remediation Magazine (BNP Media), Jim Holland.
Details, formula, and sources
ScopeDerates a nameplate AHAM pint rating to its field output as the chamber dries and the inlet grains fall, and turns the derate into the honest unit count - which goes UP, not down, as the chamber dries (the classic drying plateau). The operator reads the derate factor off the unit's own performance curve at the measured chamber GPP; the curve and psychrometric reality govern.
Formula or tableeffective_pints = aham_pints_per_day x derate_factor; units_by_nameplate = ceil(demand / aham); units_by_field = ceil(demand / effective_pints); shortfall = units_by_field - units_by_nameplate.
Source and editionANSI/IICRC S500 caution that the AHAM rating overstates field output at low grain depression, by name; the linear derate is a working-band screen.
Free accessThe AHAM rating is taken at a high-grain-depression test condition and overstates what a unit removes as the chamber dries. The multiplication is arithmetic.
What governsEstimate. AHJ and licensed professional govern.
API field namesaham_pints_per_day, derate_factor, required_pints_per_day, effective_pints, units_by_field, shortfall_units
- Derate source the operator reads the derate factor off the unit's performance curve at the current chamber grain depressionmanufacturer performance curve
- AHAM overstates field the AHAM nameplate (high-grain-depression test) overstates field output as the chamber driesANSI/IICRC S500
- Linear screen a linear derate is the working-band approximation manufacturers' curves support; not a curve fitmanufacturer performance curve