Glossary

AHU      
Air-handling unit
 
Air changes per hour
How many times the air in a building is changed on an hourly basis
 
Airflow proving switches
Airflow sensing device to prevent humidification during insufficient airflow
 
Alternate water seal
Nonstandard P-trap configuration installed before the drain valve on a steam generator
 
Amps / Current (I)
Measure of the flow of electricity; current is measured in Amps
 
BACnet
Controller language
 
BSP
British standard pipe thread
 
Building volume               
Interior building volume (i.e., ft3 or m3)
 
Condensate pump
Pump used to push condensate to a more desirable location
 
Control cabinet with time delay
Control cabinet includes the component that can delay the opening and closing of a valve or relay based on demand
 
Desired conditions
The desired final relative humidity and dry bulb temperature of a space
 
Dew point temperature
The saturation temperature corresponding to the humidity ratio and pressure of a given moist-air state
 
Dew point transmitter
Sensing device based on dew-point used to control demand for a humidifier
 
Direct steam
Live or pressurized steam as from a boiler
 
Dispersion product
Steam distributor
 
Dispersion tube insulation
Insulation applied to dispersion tubes to limit air heat gain and associated condensate losses
 
DN
(Diameter Nominal) Nominal piping measurement in millimeters
 
Drip-tee kit
Includes an inline tee connector, two hose cuffs, and four hose clamps
 
Dry bulb temperature
The temperature of the air indicated by any type of thermometer or thermocouple that has not been affected by evaporation or radiation
 
Duct
A channel or tube for conveying air
 
End-of-season drain
Opening a drain valve automatically after a period of non-use
 
F&T trap
Float and Thermostatic trap
 
Face height
Height of a dispersion assembly area where humidification steam is dispersed
 
Face width
Width of a dispersion assembly area where humidification steam is dispersed
 
Flange
A bolt-together fitting
 
Flange, screw-on
Flange that is screwed to a threaded nipple
 
Generation product
Atmospheric steam generator
 
Grains of moisture
Mass of water in grains per mass of dry air (i.e., grains/lb dry air or grains/kg dry air)
 
Hand direction
Right handed or left handed orientation of steam dispersion tube.  Facing into the airstream, where separator is located is the hand direction (left or right).
 
Hard pipe kit
Includes two hose cuffs and four hose clamps
 
Header, dispersion assembly
Central steam distribution pipe of a dispersion assembly
 
Headers inside
Central steam distribution pipe of a dispersion assembly is installed inside a duct or air handling unit
 
Headers outside
Central distribution pipe of a dispersion assembly is installed outside a duct or air handling unit
 
Heat gain from assembly
Heat transferred to the air from a dispersion assembly, which can be reduced with insulation
 
Heat gain from steam
Irreducible heat gain when steam is dispersed into air
 
High-limit humidistats
Humidity sensing device used to reduce or stop steam generation if airstream is close to saturation
 
Infiltration volume
Air volume entering a ventilation system through exterior openings (i.e., windows, doors, or leakage)
 
Input signal
Control signal
 
Insulation, dispersion tube (nonpressurized steam)
PVDF insulation applied to a dispersion tube
 
Insulation, dispersion tube jacketed (pressurized steam)
Sheet steel wrapper with insulation between the dispersion tube and wrapper
 
Insulation, tank
Insulation placed on a humidifier to prevent hot surfaces
 
Interconnecting piping
The pipe between a steam generator and dispersion assembly
 
Interoperability
Operability between humidifier and building management system, using a language such as LonTalk, BACnet, or Modbus
 
IP 66 cabinet
Control cabinet with dust and drip-proof rating
 
I-P units
Inch/pound measurement
 
Jackplate
Communication jack
 
kg/h
Kilograms per hour
 
kW
Kilowatt
 
lbs/hr
Pounds per hour
 
Load
Quantity of moisture required to meet relative humidity (RH) requirements (i.e., lbs/hr or kg/h)
 
Load plus loss
Total moisture required to meet the relative humidity plus offset steam lost as condensate formed in steam piping, measured in lbs/hr or kg/h
 
LonTalk
Control language used to communicate
 
Low-water float switch
Low water cutoff
 
Makeup-air ventilation system
Ventilation system with only outside air

Mixed-air ventilation system
Ventilation system with both return air and outside air
 
Modbus
Control language used to communicate
 

Modulating humidistat
Humidistat that produces a modulating control signal
 
Multiple-tank control
Single-point control of multiple humidifiers

Natural ventilation system
Ventilation system without the use of a mechanical device
  
NEMA-1 safety switch
External disconnect for electric humidifier
 
NEMA-12 cabinet
Control cabinet with dust proof rating
 
NEMA-4 cabinet
Control cabinet with dust and drip proof rating
 
Nonpressurized steam dispersion
Dispersion systems designed to accept steam from DriSteem steam generators
 
NPT
National pipe thread
 
Open space
Area with no ductwork

Outside air intake rate
Rate at which outside air enters a ventilation system
 
Outside air volume
Air volume entering a ventilation system from outside
 
Outside conditions
The outside dry bulb temperature and relative humidity
 
Pilot positioner
Positioning a valve using a pilot air control signal
 
Potable water
Tap (or drinking) water
 
Pressurized steam dispersion
Direct or live steam dispersion product
 
Project, DriCalc
Job name or reference number
 
Redundant tank              
Backup system or tank
 
Relative humidity (RH)
The wetness or dryness of air at a given temperature and pressure
 
Remote temperature sensor
Prevents condensation on structural members
 
Rise
The minimum nonwetting height above the steam outlet
 
RO/DI water
Reverse-Osmosis filtered, or DeIonized water
 
Same-side piping
Steam supply and condensate connection are on same side of the steam dispersion assembly
 
Sealed combustion
Air for combustion is ducted directly to a humidifier
 
Seismic certified
Humidification equipment that has gone through third party shake testing to validate operation after a seismic event.  May have additional or different support methods or structural enhancements
 
Separator
Steam and condensate separating device
 
Separator orientation
Separator may be in the upright or horizontal position
 
SI units
System International metric unit system
 
Softened water
Water where calcium and magnesium ions have been replaced with sodium ions
 
Solenoid valve
Electromagnetic valve
 
Spread
The minimum nonwetting width from the steam outlet
 
SSR sequencing modulation
One heater stage is controlled by a Solid-State Relay while others are controlled contactors
 
SSR, 100%, modulation
All heater stages are controlled by a Solid-State Relay
 
Steam dispersion enclosure
Box that contains the header
 
Steam dispersion panel
Dispersion system with a frame or case
 
Steam hose
Hose that connects a steam generator to a dispersion assembly and designed to withstand high temperatures
 
Steam trap
Device that prevents steam flow but allows condensate to flow through
 
Steam valve Cv/Kv
Flow coefficient of a valve
 
Steam valve size
Inlet and outlet size of the steam valve body
 
Steam-to-steam
Generating nonpressurized steam via direct steam and a heat exchanger
 
Strainer               
Steam filter upstream of the steam valve to remove debris
 
System (DriCalc)
Humidification system for a space
 
Tag name
Individual humidifier identification
 
Temperature switch
Temperature activated switch prevents the operation of a control valve
 
Throw
The minimum nonwetting horizontal distance from the steam outlet
 
Total air volume
Total volume of air in a ventilation system
 
TP modulation
Time-proportioned modulation
 
Trapeze               
Hanging support system for a humidifier
 
Tube spacing on-center
Spacing between dispersion tubes, measured from the tube center line
 
Tubing
Thin walled pipe designed to withstand high temperatures
 
Tubing, insulated
Thin walled pipe with insulating cover
 
Vac
Volts alternating current
 
Valve control, electric
Electric control signal for steam valve(s)
 
Valve control, pneumatic
Pneumatic control signal for steam valve(s)
 
Venting, horizontal
Side wall venting
 
Weather cover
Enclosure that prevents rain from wetting humidifier components
 
Wet bulb temperature
An expression of the temperature of the air when a wick or sock, wetted with water, encases the sensing element of a dry bulb thermometer and air is passed over it at a velocity of 700 feet per minute or more
 
Y connector kit
Includes a Y connector, three hose cuffs, and six hose clamps