VA |
VOLT AMPERE |
VAC |
VOLTS ALTERNATING CURRENT |
VACUUM |
A PRESSURE THAT IS LESS THAN ATMOSPHERIC PRESSURE |
VARIABLE AIR VOLUME |
ALSO REFERRED TO AS "VAV", WHICH IS A SYSTEM THAT CONTROLS SPACE TEMPERATURE BY VARYING THE QUANTITY OF SUPPLY AIR RATHER THAN BY VARYING THE TEMPERATURE OF THE SUPPLY AIR |
VARIABLE FREQUENCY DRIVE |
A DEVICE OFTEN REFERRED TO AS A SPEED DRIVE WHICH VARIES THE VOLTAGE TO AN ELECTRIC MOTOR TO VARY THE SPEED OF THE MOTOR |
VAV |
SEE "VARIABLE AIR VOLUME" |
VDC |
VOLTS DIRECT CURRENT |
VELOCITY POSITION PROPORTIONING |
A CONTROL METHOD WHERE VALVE POSITION IS DETERMINED BY CALCULATING THE AMOUNT OF TIME IT TAKES TO OPEN OR CLOSE A VALVE BY MOVING THE VALVE FOR A PORTION OF THAT TIME |
VELOCITY PRESSURE |
PRESSURE THAT IS CAUSED BY AIR BEING IN MOTION, AND HAS A DIRECT RELATION TO THE VELOCITY OF THE AIR |
VENTURI |
CREATES NEGATIVE PRESSURE AND INCREASED GAS FLOW VELOCITY DUE TO THE WAY IT NARROWS AND THEN FLARES-OUT; A SECTION OF THE BURNER |
VFD |
STANDS FOR VARIABLE FREQUENCY DRIVE |
VITON |
EXTREMELY CHEMICALLY RESISTANT FLUOROPOLYMER USING PLASTICIZING AGENTS TO INCREASE FLEXIBILITY. |
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WATT DENSITY |
MEASURED IN UNITS OF WATTS PER SQUARE INCH, SUCH AS THE WATTAGE WHICH COMES FROM A SQ. INCH OF THE SURFACE OF AN ELECTRIC HEATER OR HEATER ELEMENT. |
WET-BULB TEMPERATURE |
AIR TEMPERATURE THAT IS MEASURED BY A WET-BULB THERMOMETER AND THAT IS LOWER THAN DRY-BULB TEMPERATURE IN INVERSE PROPORTION TO THE HUMIDITY. HOWEVER, THIS DOES NOT APPLY WHEN/IF THE AIR IS SATURATED |
WILD STREAM |
IN MIXING APPLICATIONS THAT REQUIRE MATERIALS TO BE MIXED TO A DESIRED RATIO, THIS IS THE ONE PART OF THE MATERIAL THAT IS UNCONTROLLED |
WINDUP |
SATURATION OF THE INTEGRAL MODE OF A TEMPERATURE CONTROLLER DEVELOPING DURING TIMES WHEN CONTROL CANNOT BE ACHIEVED, WHICH CAUSES THE CONTROLLED VARIABLE TO OVERSHOOT ITS SETPOINT WHEN THE OBSTACLE TO CONTROL IS REMOVED |
|
ZONE |
A SPACE OR MULTIPLE SPACES (USUALLY ROOMS) WITHIN A BUILDING WITH HEATING AND/OR COOLING REQUIREMENTS THAT ARE VERY SIMILAR SO THAT THE COMFORT CONDITIONS CAN BE MAINTAINED THROUGHOUT BY ONE SINGLE CONTROLLING DEVICE |
ZONE CONTROL |
WHEN A BUILDING IS DIVIDED INTO SEVERAL ZONES, AND EACH ZONE CAN BE CONTROLLED INDEPENDENTLY |
ZONED REHEAT |
PROVIDES ZONE CONTROL FOR AREAS OF UNEQUAL LOADING & SIMULTANEOUS HEATING OR COOLING OF PERIMETER AREAS WITH DIFFERENT EXPOSURES. HEAT IS ADDED TO (AS A SECONDARY PROCESS) TO PRECONDITIONED PRIMARY AIR OR RECIRCULATED ROOM AIR |
