Unit 13 & 14 Test Flashcards
(20 cards)
The automatic control of a system is intended to ____.
maintain stable or constant conditions without excessive human interference
Modulating controls are used to ____.
vary the speed of a motor
When a control is required to control space or product temperature, it is called a ____.
thermostat
A thermal system overload may occur if a specific electrical or mechanical component is not cooled properly, resulting in ____.
overheating
The compressor in the refrigerator has a protective device that keeps it from overloading and damaging itself. This device is called a(n) ____.
overload
The metals most often used in a bimetal temperature control are ____.
brass and steel
An example of a bimetal device is a ____.
snap-disc
A thermocouple is a device that ____.
converts heat to electrical energy
Brass and steel have a different rate of expansion and contraction when heated or cooled.
true
Fluid expansion is a way to sense temperature change.
true
The purpose of a heat anticipator is to ____.
reduce the temperature swing of a conditioned space
The difference between system overshoot and system lag is called ____.
temperature swing
The heat anticipator in the thermostat control circuit in the heating mode is active when the ____.
heating contact is closed
The heater in the thermostat control circuit in the cooling mode is active when the ____.
cooling contact is open
Line voltage thermostats have heavier contacts and use which type of sensing element?
All of the above.
A low pressure control has a “high event” and a “differential” setting. The technician wants the system to turn on at 28 psig and shut down at 2 psig. What would be the proper settings?
High event: 28 psig, differential: 26 psig.
Oil pressure safety controls measure the difference in pressure to establish ____.
that positive oil pressure is present
To control ice build-up on a heat pump outdoor coil in the heating cycle, a ____ is attached to a large diaphragm.
micro-switch
The heat anticipator in a thermostat prevents the temperature in the conditioned space from rising above the thermostat setting.
True
The advantage of using a thermistor-type thermometer over a mercury-filled thermometer for measuring refrigerant line temperature is that the thermistor-type does not have to be insulated.
False
