_____ is a standard protocol that allows control units from different manufacturers to pass data to each other.
Explore more HVAC questions
for other HVAC topics now!
The resistance value of RTDs increase with decrease in temperature:
Removal of latent heat will:
The downstream velocity of the sound wave in Ultrasonic flow sensors between the points is ______ than that of the same wave in a fluid at rest.
In which of the following control action high overshoot and undershoot occurs:
The temperature – resistance characteristics of RTDs is _____:
The purpose of this closed loop control system is to maintain the controlled variable to some desired value:
The evaporator H coil is normally used in horizontal applications
______ is the number of positions an actuator will assume when the control signal is slowly changed 0 – 100%
A floating control response produces _____ number of digital outputs based on a change in an analog variable input:
Which one of the following is less reliable and noisier:
For medium and high pressure ducts, ________ sheets are exclusively used for strength and rigidity to withstand the higher static pressure:
The condensing unit must be located at the lower level than expansion coil in an air conditioning system to avoid pressure drop in the refrigerant
A mixing valve can also be used in a bypass application to control the flow through the coil by placing the valve _____ of the coil:
Typical voltage input ranges for sensor is _______ :
With respect to the elevation, atmospheric pressure decreases approximately _____ for 1000 ft of the ascent
BALCO RTDs have which of the following element compositions:
Which of the following is sensors located in each main return air duct for controlling outdoor air/return mixing dampers or the outdoor air fans:
Air velocity in the ducts must be kept reasonably ________ to minimize the frictional losses:
Removal of _____ lowers the air temperature
_____ is the actual mass of water vapor in one cubic foot of air:
Type of signals from the controllers can be which of the following:
_____ temperature coefficient Thermistors are most commonly used for temperature measurement.
The error signal generated in closed loop system is fed to which of the following:
The best control stability is accomplished when there is a _____ relationship between the position of the valve stem and the heat output from the coil.
In which of the control system sensor measures the control variable:
Which of the following is temperature measuring sensors:
In a microprocessor-based system, the sensor input is converted to which of the form
The difference between the temperatures at which the controller turns ‘on’ or ‘off’ is called the:
When the velocity of the air in the duct reduces, the resulting velocity pressure difference gets converted to ______ pressure:
Valve characteristics for a typical cooling coil and a heating coil are same:
____ temperature is the sensible–heat level of air and is taken with an ordinary thermometer
In a Proportional controller when the measured value is greater than the set point, then the correction signal will be _____ :
Which one of the following control system is also known as “Feed Forward Control System”
While calculating the cooling load estimate for a house, each person is given an allowance of _____:
The effect of varying speed with a centrifugal pump is to vary which of the following quantity:
Gas piping systems that are to be supplied with a gas of a specific gravity of ______ or less can be sized directly from the tables provided in the international fuel gas code.
The purpose of reheat coils in the air conditioning system is to _____ the relative humidity in the room when the sensible load comes down:
What part of the code allows the inspector to make rules concerning the reuse of equipment?
Oxygen depletion safety systems shall shut off the gas supply to the main and pilot burners when the oxygen in the surrounding atmosphere is depleted to the percent concentration specified by the manufactuer, but not lower than ______ percent.