Equipment & installation
Acronyms, system components, tubing, fittings and mounting terms.
How to use this reference
Browse by category or search the Resources library for a term or part number. The web glossary brings the source entries into readable tables; the original PDF remains available below.
Definitions help identify concepts and components. Use the linked equipment and service guides for model-specific ratings and procedures. Standards named here are references, not a claim of equipment certification.
Acronyms & abbreviations
| Abbreviation | Meaning |
|---|---|
| ACH | Air changes / exchanges per hour |
| ANSI | American National Standards Institute |
| ANSI/HI | ANSI / Hydraulic Institute |
| APS | Automated pump station |
| ASHRAE | American Society of Heating, Refrigerating and Air-Conditioning Engineers |
| ASME | American Society of Mechanical Engineers |
| BAS/EMS | Building automation / energy management system |
| CFM | Cubic feet per minute |
| EDV | Electric drain valve |
| EMC | Equilibrium moisture content |
| ER | Evaporation ratio: CFM per lb/hr of water output |
| ESD | Electrostatic discharge |
| ExA | Exhaust airflow |
| FNPT | Female National Pipe Thread |
| FSC | Final system capacity |
| GD | Grains difference, grains/ft³ |
| GHT | Garden hose thread |
| GPM | Gallons per minute |
| HP | Horsepower |
| HPS | High-pressure safety switch |
| HRO20 | Neptronic humidistat model |
| HVAC | Heating, ventilation and air conditioning |
| ID | Inside diameter |
| ISO | International Organization for Standardization |
| LOTO | Lockout/tagout |
| MAU | Makeup-air unit |
| MNPT | Male National Pipe Thread |
| MSD | Moisture-sensitive device |
| MuA | Makeup airflow |
| NEC | National Electrical Code |
| NFPA | National Fire Protection Association |
| NPT | National Pipe Thread |
| OD | Outside diameter |
| OSHA | Occupational Safety and Health Administration |
| PLC | Programmable logic controller |
| PPE | Personal protective equipment |
| PSI | Pounds per square inch |
| RH | Relative humidity |
| RO | Reverse osmosis |
| ROI | Return on investment |
| RTO | Regenerative thermal oxidizer |
| RTU | Rooftop unit |
| SS | Stainless steel |
| TAB | Test and balance |
| TDS | Total dissolved solids |
| TMC | Target moisture content |
| UL | UL / Underwriters Laboratories |
| UNC | Unified National Coarse thread |
| VAC | Volts alternating current |
| VOC | Volatile organic compound |
System & equipment components
| Term | Meaning |
|---|---|
| Pump Station | The enclosed equipment package housing the pump, PLC controller, and associated safety/control devices that generates and regulates 1000-psi water for the system. |
| PLC Controller | The programmable logic controller (Omron) inside the pump station that manages pump/fan sequencing, timers, and safety shutdowns. |
| Electric Drain Valve (EDV) | A Danfoss 2/2-way, normally-open solenoid valve on the pump discharge manifold that releases line pressure on shutdown to mechanically close the nozzles. |
| High-Pressure Safety Switch (HPS) | Pressure-proof switch used by the PLC to shut the pump down when pressure is not established or is lost. The black switch reference lists a nominal 580 psi activation; the sequence describes proving approximately 550 psi within the configured interval. |
| Unloader Valve | Regulates approximately 1,000 psi discharge pressure and returns pump bypass capacity to the inlet. Excessive bypass can heat the returned water; use the current unloader guide to evaluate sizing and thermal relief. |
| Thermal Relief Valve | Opens automatically if water temperature inside the pump exceeds 145°F. |
| Low-Pressure Inlet Solenoid Valve | Maintains proper water volume and pressure into the pump from the incoming supply; functions as an automated, normally-closed "smart faucet" for the pump's low-pressure inlet side. |
| 24 VAC Transformer | Supplies low-voltage power for the humidistat and fan control circuits. |
| Fan Manual Override Toggle Switch | Allows independent testing of fan rotation from the pump station without a humidistat call. |
| Humidistat | Wall-mounted RH sensor/controller (Neptronic HRO20) that sends the start/stop signal driving the PLC's pump and fan cycling. |
| Mist-Ring | A stainless-steel ring carrying the nozzle ports, mounted to the face of each fan to distribute atomized water evenly into the airstream. |
| Nozzle | A stainless-steel, ruby-orifice atomizing tip threaded into a Mist-Ring port; mechanically opens and closes at a set cracking pressure. |
| Ball Valve Assembly | The fitting assembly connecting a fan's drop-down tube to its Mist-Ring, allowing that fan to be isolated for flushing or service. |
| Fan Contactor Relay Box | A remote junction box containing a contactor that switches plant power to a fan on the low-voltage signal from the pump station. |
| Bladder (Expansion) Tank | A pressurized reclaim tank that can capture the EDV's drain release back into the pump's low-pressure water supply instead of sending it to waste. |
| Diaphragm (Solenoid Valve) | The internal rubber component inside a water inlet solenoid valve that controls flow; if torn, out of position, or scaled, the valve will allow flow when off or restrict flow when on. Replacing the whole valve body is recommended over repairing the diaphragm alone. |
Tubing, fittings & hardware
| Term | Meaning |
|---|---|
| High-Pressure Tube | Black nylon (Polyamide 12) tubing rated for 1000- psi operation, used in 1/2" and 3/8" sizes throughout the system. |
| Slip-Lok Fitting | A push-to-connect fitting system for high-pressure nylon tubing; tool-free to install and service. |
| Slip-Lok Coupling | A fitting that joins two lengths of same-diameter tubing to extend a run. |
| Slip-Lok 90° Elbow | A fitting that changes tubing direction 90°; used sparingly in favor of bending the tube itself. |
| Slip-Lok Three-Way Tee | A fitting that splits or combines flow, such as branching off to a drop-down line. |
| Transition Fitting | A Slip-Lok x NPT adapter that steps a run down from 1/2" to 3/8" tubing as it branches toward the fans. |
| Primary O-ring | The oversized internal O-ring inside a Slip-Lok fitting that compresses against the tube to form the leak-proof seal. |
| Backup Urethane O-ring | An optional secondary O-ring that buffers the ferrule teeth from the primary O-ring, extending fitting life. |
| Ferrule | The internal locking element inside a Slip-Lok collar that grips the tube once it is inserted and tugged back. |
| Drop-Down Tube | The 3/8" tube run connecting the ceiling-routed high-pressure line down to each fan's ball valve assembly. |
| Wall Clamp | A vinyl-coated steel clamp used to secure tubing to walls or structural supports. |
| Plumber's Tape | Thread-sealing tape applied to every threaded (NPT) connection in the system. |
| Compression Fitting | A stainless steel or brass fitting that connects rigid tube (typically stainless steel pipe) without welding or soldering; a nut and ferrule compress around the tube to create a leak-resistant seal. |
| Bulkhead Fitting | A fitting designed to pass through a panel or wall connection point (e.g. drain bypass on older pump stations), rather than joining two lengths of tube in-line. |
Installation & mounting terms
| Term | Meaning |
|---|---|
| Moisture Plume | The region of atomized mist projected into the air by a fan. The reference layout allows approximately 4 feet in diameter by 22 feet of unobstructed travel; actual evaporation depends on airflow, nozzle output and room conditions. |
| Fan Bracket | The mounting hardware that attaches a fan to structural steel, angle iron, or a wall. |
| Angle Iron | Structural steel used as a ceiling-truss mounting point for fan brackets. |
| Ceiling-Hung Mounting | Method of suspending a fan from ceiling truss angle iron rather than a wall or column. |
| Drip Loop | A deliberate downward loop in fan supply wiring that directs accumulated condensation away from the motor housing. |
| Local Disconnect Switch | A dedicated on/off switch installed at each fan for independent maintenance control. |
| Coil Memory | The tendency of coiled nylon tubing to retain its rolled shape; relaxed by uncoiling and warming before routing. |
| Deburr | Lightly filing or sanding a freshly cut tube end smooth before inserting it into a fitting. |
| 180° Sweep | A flexible bend formed in the drop-down tube that allows a straight connection into the ball valve assembly. |
| Daisy-Chain Order | The fan-by-fan installation or flushing sequence, proceeding outward from the pump station. |
Controls, operation & care
Electrical terminology, operating parameters, water quality and maintenance.
Electrical & controls terminology
| Term | Meaning |
|---|---|
| Fan/Pump Delay | PLC-controlled sequencing: fans start 10 seconds before the pump; on shutdown, fans continue running 10 seconds after the pump stops. |
| Pressure-Build Timer | The PLC's timed window — 25 seconds in normal operation, 60 seconds on initial startup — for the pump to reach 550 psi before faulting off. |
| Strain Relief | A fitting at a pump-enclosure cable entry point that protects wiring from mechanical stress. |
| Normally Open (NO) | A valve or relay-contact state when not energized. For the EDV, normally open means water can discharge when coil power is off; energizing the coil closes the drain. |
| Terminal Block (TB1) | The humidistat's internal wiring strip; only 3 of its 16 positions (Common, 24VAC, Humidify Output) are actually used. |
| Setpoint | The target RH% programmed into the humidistat that determines when the system cycles on and off. |
| Dead Band | The gap between the RH that starts the system and the RH that stops it; a wider setting reduces cycling frequency. |
| Proportional Band | The RH range over which the humidistat modulates its control response. |
Operating parameters & specifications
| Term | Meaning |
|---|---|
| System Operating Pressure | The normal FanMist high-pressure operating setting, approximately 1,000 psi. Manufacturer maximum component ratings are not alternate station operating settings. |
| Cracking Pressure | The 300-psi threshold at which a nozzle's internal spring mechanically opens to atomize water. |
| Burst Rating | A component failure-pressure rating, distinct from its allowable operating pressure. The source lists 2,500–2,800 psi for its tubing; the system operates at approximately 1,000 psi. |
| Evaporation Rate (ER) | The FanMist sizing ratio of fan airflow in CFM to water output in lb/hr. The installation handbook cites 80 or higher; the nozzle and load references cite greater than 75. Use actual fan and nozzle ratings for the calculation. |
| Operating Cycle | A recurring humidity call followed by a satisfied period. The reference uses ten minutes on and ten minutes off as a typical illustration; actual cycling depends on demand and controls. |
| Average Seasonal Runtime | Typical annual operating hours — 1,500–2,000 — during the humidification season (Oct 15–Apr 15). |
Water treatment & quality terms
| Term | Meaning |
|---|---|
| Pre-Filter | A 5-micron cartridge filter on the incoming water line that protects the pump and nozzles from particulate. |
| Scaling | Mineral deposits on wetted surfaces. Treatment depends on the water analysis; softening and scale-control systems address scale differently and do not necessarily remove dissolved minerals. |
| Air Dusting | Airborne residue left when water containing dissolved minerals evaporates. RO reduces dissolved minerals; hardness control alone does not eliminate all dissolved solids. |
| Water Softener | Equipment that reduces water hardness to prevent scaling. |
| Reverse Osmosis (RO) | A water treatment method that removes dissolved minerals to prevent air dusting. |
Procedures & maintenance terms
| Term | Meaning |
|---|---|
| Lockout/Tagout (LOTO) | OSHA 1910.147 procedure for isolating hazardous energy sources before servicing equipment. |
| Flushing Procedure | Mandatory pre-startup step that runs water through the system, nozzles removed, to clear installation debris before nozzles are installed. |
| System Startup | The sequenced procedure for bringing the system online and confirming correct pump, fan, and pressure operation. |
| Pre-Start Fan Testing | Verifying correct fan rotation using the manual override switch, both before and after final wiring. |
| Warranty Claim | The formal process for requesting repair or replacement of a defective component under the manufacturer's warranty terms. |
Physics & load calculation
Scientific principles and the terms used in sizing worksheets.
Physical & scientific principles
| Term | Meaning |
|---|---|
| Dalton’s Law & the Ideal Gas Law | Dalton’s law describes each gas’s contribution to total pressure, including water vapor. The ideal-gas approximation supports many air and vapor calculations. Air movement and mixing distribute moisture through a space. |
| Fick's Laws of Diffusion | Describe diffusion down a concentration gradient. They do not assign water vapor a universal travel speed; bulk fan airflow and turbulent mixing also affect distribution. |
| Clausius-Clapeyron Equation | Describes how saturation vapor pressure changes with temperature. Warmer conditions require more water vapor to reach the same RH; the rate of change depends on temperature. |
Load calculation & psychrometric terms
| Term | Meaning |
|---|---|
| Governing Airflow | The single most important input for a load calculation: the greater of total exhaust CFM or total makeup-air CFM (or an estimated ACH when CFM data isn't available). Whichever is larger drives the load calculation. |
| Air Balance | The relationship between a building's exhaust-air CFM and makeup-air CFM; determines how much of the building's air exchange is deliberate (ventilation) versus incidental (infiltration). |
| Ventilation | The deliberate, engineered exchange of air with the outdoors — process exhaust systems pulling air out, makeup-air units/economizers/supply fans bringing tempered air back in. Measured and usually preconditioned. |
| Infiltration | The uncontrolled counterpart to ventilation: outdoor air leaking in through door gaps, dock doors, wall penetrations, and envelope imperfections, filling whatever gap a building's air balance leaves. |
| Negative Pressure (Building) | Condition where exhaust CFM exceeds makeup-air CFM; the building pulls more air out than it replaces, drawing the shortfall in through infiltration. In this case exhaust CFM is the more representative governing figure. |
| Positive Pressure (Building) | Condition where makeup-air CFM exceeds exhaust CFM; more air is pushed in than removed, suppressing infiltration (sometimes at the cost of excess conditioning capacity). |
| Balanced Pressure (Building) | Condition where exhaust and makeup-air CFM are approximately equal; infiltration is minimal and measured makeup-air CFM is a trustworthy load input. |
| Grains/ft3 Difference | Target indoor water-vapor content minus the outdoor-air moisture allowance, expressed in grains per cubic foot. The guide’s 50% factor is a conservative outdoor-moisture assumption, not moisture lost simply by heating air. |
| Load | The total amount of moisture, in pounds of water vapor per hour, that the FanMist system must add to bring incoming air up to the target RH under design winter conditions. The central concept of the Load Calculator Guides. |
| Final System Capacity | Load plus a 15% safety margin (baseline; higher- throughput or tighter-tolerance facilities may reasonably size larger), accounting for colder-than- design temperatures and minor operating variation. |
| Psychrometric Saturation Table | Reference table (Table 2-A in each guide) showing grains of water vapor per cubic foot of air at 100% saturation for a given temperature; the basis for all load-calculation moisture lookups. Key conversion: 7,000 grains = 1 lb of water. |
| Target Moisture Content (TMC) | The grains/ft3 value at target indoor RH% and temperature (saturation grains/ft3 × desired RH%). |
| Grains Difference (GD) | The moisture deficit in grains per cubic foot used in the practical load formula. Calculate from the indoor target and the chosen outdoor-moisture allowance. |
| Formula #1 (CFM Basis) | The preferred practical sizing method: Load (lbs/hr) = Grains/ft3 Difference × (Governing CFM × 60) ÷ 7,000 grains/lb. Used when exhaust/makeup-air CFM data is known. |
| Formula #2 (ACH Basis) | Alternate practical sizing method used when CFM data isn't available: Load (lbs/hr) = Grains/ft3 Difference × (Total Volume ft3 × ACH) ÷ 7,000 grains/lb. |
| Practical Method | The reference’s initial sizing approach: replacement-air volume multiplied by moisture deficit, followed by an explicit capacity margin. Secondary product, process and occupancy effects require separate evaluation when material. |
| Comprehensive Method | Sizing method that builds on the Practical Method by adding secondary load factors (Product Regain, Process Vapors, People) for more precise calculations — used for high-throughput facilities or tight tolerance targets. |
| Product Regain | Secondary load factor (moisture sink, increases load): dry incoming stock (lumber, paper rolls, PCBs/components) absorbs moisture from shop air as it reaches equilibrium, requiring additional humidifier output. |
| Process Vapors | Secondary load factor (moisture gain, decreases load): water vapor released by certain operations (finishing/spray booths, glue curing, ink/coating drying, aqueous cleaning) partially offsets the humidification need. |
| Economizer | HVAC controls that vary outdoor-air intake. Use actual winter outdoor-air settings and design airflow when estimating makeup air; a damper percentage is not a universal ventilation requirement. |
| Freeze-Protection Lockout | A low-temperature control sequence that can change HVAC operation. Confirm the actual unit’s winter outdoor-air delivery from its design and controls before using it in a load calculation. |
Processes & references
Industry-specific concepts and standards named in the source.
Industry-specific process terms
| Term | Meaning |
|---|---|
| Hygroscopic | A material that exchanges moisture with its surroundings as it approaches equilibrium. Wood and paper are common examples. |
| Web Break | A tear or break in a moving paper web; moisture variation, tension and static are among possible contributing factors. |
| Static Electricity (Paper/Print) | Charge produced during contact and separation at rollers and guides. Humidity can affect surface conductivity and charge dissipation, alongside other process controls. |
| Electrostatic Discharge (ESD) | A discharge that can damage sensitive electronics. Humidity control complements grounding, ionization and ESD-safe handling; it does not replace them. |
| Moisture-Sensitive Device (MSD) | An electronic package with specified moisture-exposure and storage requirements. Follow its manufacturer and the applicable handling procedures. |
| Floor Life | The permitted exposure time of a moisture-sensitive device under its specified conditions after removal from protective packaging. |
| Triboelectric Charge | Charge generated by materials contacting and separating, including handling, conveyors and packaging. Humidity can affect how quickly it dissipates. |
| ISO Cleanroom Classification | A classification of airborne particle cleanliness. Use the room’s actual mechanical and process design when evaluating humidity and outdoor-air load. |
| ANSI/ESD S20.20 | An ESD-control-program standard referenced by the electronics guide; a room humidity target alone does not establish program compliance. |
| Fully Exhausted Process Stream | Process air discharged outdoors rather than returned to the served space. Count the actual outdoor discharge in the air balance. |
| Recirculating Exhaust | A process extraction system that returns some appropriately treated air indoors. Count the portion actually lost outdoors and verify any assumed loss fraction. |
| Regenerative Thermal Oxidizer (RTO) | Equipment used to treat certain process exhaust streams. Confirm its actual operating airflow when estimating the plant’s outdoor exhaust. |
Standards & referenced codes
| Term | Meaning |
|---|---|
| NEC / NFPA 70 | Electrical installation code referenced by the source. The applicable edition and local requirements are determined for the installation. |
| OSHA 1910.147 | Hazardous-energy control / lockout-tagout reference named in the source. |
| OSHA 1910.132 | Personal protective equipment reference named in the source. |
| ASME B31.3 | Process-piping code referenced in the source; its mention does not establish certification or project-specific applicability. |
| ANSI/HI 1.6 | Hydraulic Institute pump standard referenced in the source. Confirm the correct applicable standard with the equipment manufacturer. |
| ASHRAE 188 | Legionellosis risk-management standard referenced in the source. Scale control and RO do not by themselves establish a complete water-management program. |
| ASHRAE 62.1 | Ventilation for acceptable indoor air quality standard referenced in the source. Confirm project-specific ventilation requirements with the mechanical design team. |
| ANSI Z535 | Safety-color, sign and labeling standards referenced in the source. |
| UL 508A | Industrial-control-panel standard referenced in the source. A glossary reference is not a statement that a particular panel is listed or certified. |
Parts & references
Continue with related guides, parts and the original PDF.
Original & related PDFs
This web guide is adapted from the IHC reference linked below. The original PDF retains its diagrams, document revision and printable layout.