WEEK 4 CHAPTER TEST REVIEW 20/22

1amp of current is equal to

1 coulomb

In a paralled circuit with a voltage drop of 120 v what would be the voltage drop of the circuit

120 v

The pickup voltage require to operate a potential relay is generated when a motor reaches around ____ percentage of its operating speed?

75% or 3/4

The main purpose of a metering device's orifice is to produce

A Pressure Drop

Which of following statements regarding stepper motor EEV's is not true?

A stepper motor regulates flow as it responds to a PWM signal by opening and closing rapidly.

When two substance are mixed and become one substance what occurs

Absorbtion

Checkvalve that open insuffuciently will allow what.

Act as a throttling device create and unanticiapated pressure drop

When a thin layer of fluid adheres to a solid but the two substances are not mixed together ______ occurs

Adsorption

Some HVACR systems require special TXVs to accomodate

All of the Above

When high head pressure in a hermitc system causes a oil and refrigerant breakdown the pressence of moisture or dirt can result in what being formed

All of the Above (sluge, acids, carbon)

Capillary tube failure will most likely occur when it is

Bent or Crimped

What is valve that premit fluid flow in one direction

Check Valve

The four major components of a mechanical refrigeration system are

Compressor, Condenser, Evaporator and Refrigeration metering device

A move heat through a solid object

Conduction

A movent of heat by means of fluid.

Convecition

An EEV controls its orfice using an

Electric Operator

Solenoid valves are controlled by an

Electric Signal

When used TXV valve the term superheat refers to the difference in temperature between

Evaporator inlet and sensing bulb

If the pressure in a sensing bulb is ______ the combined pressure from the evaporator and the spring a TXV's valve is forced open

Greater Than

When capillary tube systems cycle off

High side and low side pressures equalize

How do you calculate current

I=V/R

When heat is added to substance without a rise in temperature the process is called?

Latent Heat of Vaporazation

In a capillary tube system if there is too much refrigerant in the system (overchage) what could happen

Liquid refrigerant could be drawn into the compressor damaging

The minimum ___ setting is the point that casuses the least sensing bulb temperature change while the system is running

Minimum Stable Signal

A TXV is operating properly when the evaporator is filled

Mostly with Liquid

What do ladder diagram show.

None of the Above

What changes inside the sensing element with temerpature.

Pressure

In a HVACR system can be design to use lower torque compressor motor if a TXV is equipped with

Pressure Limiter

During normal operation many EEV controllers are able to use as inputs to govern valve position and operations

Pressure Measurements and Temperature

Whats the primary purpose of the metering device.

Pressure drop

This type of metering device varies refrigerant flow by varying the speed by which a solenoid valves opens and closes

Pulse width Modulation Signal

A PWM solenoid EEV controls its valve operating by___

Rapidly opening and closing its solenoid valve

Capillary tubes are used extensively in _____ system

Refrigerator and window ac unit

During the offcycle as the sensing bulb pressure and lowside pressure cancels each other out the ____ pressure is enough to force the txv firmly into its seat

Spring pressure

The condition in which liquid refrigerant is present in only of the evaporator is called

Starving

For increased system efficiency a capillary tube is usually positioned so that a portion of it is in contact with the ______

Suction Line

After a compressor burnout what will you installed temporaily to protect the compressor for the duration of clean up

Suction Line Filter Drier

A controller modulates the EEV through the use of an algorithm to maintain the desired

Super Heat

For a TXV adjusted to its MSS point, increasing spring tension on a TXV's adjustment screw will result in an increase of

Super Heat

The main value that influences the operation of a TXV is

Super Heat

What is function of an EEV design to maintain

Super Heat

Increasing _____ this adjustment will starve the evaporator.

SuperHeat

If an AXV is undercapacity for its application, what will happen

The evaporator will be starved

On system with small-diameter horizontal suction lines the sensing bulb should be mounted on the_____of the suction line

Top

A normally open contact is between L and S True or False

True

A relay coil is between the L and M terminal

True

True or False Terminal M is connected to the motor running winding

True

When should a TXV reduce the flow rate through an evporator

as it Evporator Cools

A compressor must start while under load if an automatic expansion valve does not have

bleed or by pass

The sizing of a filter drier is primarily based on a system

capacity rating

What do pictorial diagram show.

color of wires

To maintain a constant pressure in the evaporator when the system is running an AXV______ when evaporator pressure begins to increase

decrease refrigerant flow

A hot-gas defrost valve directs refrigerant into the low side from the______

discharge line

When a TXV is feeding refrigerant into an evaporator with multiple circuits a(n) ________ should be installed

distributor

A current relay is wired by connecting an ungrounded wired connected to the m terminal

false

To help prevent contamintat from entering capilalry tube what is usually installed in its inlet

filter drier

The inefficient operation of a check valve may cause a(n) _____ noise

hammering

Piston-type metering orifice are most often used on___ system

heat pump

What is movement of heat by way of fluid flow called

hot to cool

How do scroll compressor move refrigerent

involute sprials

When a capillary tube has a large diameter what must be done to the length of the cap to have the same affect of the smaller diameter

it must be shorter

To maintain constant pressure in the evaporator when a system is running AXV does what to refirgerant flow when the evporator pressure drops

it will Increase

A system equipped with a pilot-controlled thermostatic expansion valve is likely to be a _____________

larger, (50 tons and over)

The orifice size of the metering device may need to be change for units for long ____ sets to account for extra refrigerant charge

line sets

When a capillary tube is replace it is good practice to also replace the

liquid line filter drier

This is condition in which to much refirgerant is in the evaporator and can be drawn into the the compressor

liquid slugging

The primary purpose of an AXV is to maintain constant_______

low side pressure

Metering devices that change there orfice size to account for changes in cooling loads are refered to as

modulating

A color changing element in a moisture indicator is design to change color based on?

moisture

Liquid line filter drier needs to be replace when?

moisture indicator indicates too much moisture and there is a pressure drop across the filter drier.

An advantage of capillary tubes over modulating metering devices is that capillary tubes have no

moving parts

A difference from set point and control point is

offset

Where will a TXV sensing bulb be mounted

on the outlet

The adjusting nut or screw on a thermostatic expansion valve is sensitive and should not be turned more than _____ while the unit is running.

one-quarter (1/4)

On a capilary tube system severe frosting on the suction line during compressor start up will be an indication of what

overcharge

An HVACR system can be designed to use a lower torque compressor motor if the TXV is equipped with a(n) _______

pressure limiter

Pressure reading in system using an EXV is supplied from a ____ connected to the suction line

pressure transduce

Heat that cause a change in temperature in a substance is called

sensible heat

Bubbles in a sight glass can indicate?

shortage of refrigerant/partially clog filter drier.

A small viewport installed in a refrigerant line describes a_____

sight glass

If the superheat setting is increased to correct for an oversized TXV orifice, the evaporator will be______ much of the time

starved

An AXV that is overcapacity may allow too much refrigerant into the evaporator and may cause condensation on the_______

suction line

A sensing bulb must not be affected by the air or liquid being cooled. It should be wrapped in insulation so that only ______ affects the bulb

suction line temperature

A controller modulated the EEV through the use of an algorithm to maintain the desired

superheat

If the orifice of a TXV is oversized, too much refrigerant will pass into the evaporator and cause the suction line to________ before the sensing bulb can close the valve

sweat or frost

When a capilary serves the function as both liquid line and metering device where is it connected between?

the evaporator and condenser

What is adsorbtion

the process by which a solid holds molecules of a gas or liquid or solute as a thin film

Before a sensing bulb is installed, use steel wool to clean

the sensing bulb and suction line

To prevent a TXV from opening intermittenly during the off cylce, a(n) _____ can most easily be used to automatically divert high side pressure to underside of the TXV's diaphragm during Off cycle

three way solenoid valve

The pilot valve on a four-way solenoid valve

uses high pressure vapor to operate the four way valve