UA HVAC Star Mastery

Question 1

For applications where quiet operation and light axial load characteristics are found, the type of bearing normally used is the ________.

Answer 1

Sleeve Bearing

Sleeve bearings are reliable bearings when used for small motors with light loads. Further, they offer quiet operation, which is important when used in applications close to the conditioned space.

Question 2

Sleeve bearings with an oil port lubrication system must be lubricated with the proper oil because________.

Answer 2

A. Oil that is too thin, will allow the shaft to run against the bearing surface.

B. Oil that is too thick will not run into the clearance between the shaft and the bearing surface.

C. The correct oil allows the motor shaft to float on a film of oil between the shaft and the bearing surface.

D. All of the above

Question 3

Too much grease in a grease lubricated ball bearing ______.

Answer 3

Causes Overheating

The most common cause of overheating in a ball bearing is excess grease.

Question 4

The maximum desirable operating temperature of a ball bearing is _______.

Answer 4

180°F

A bearing hotter than 180°F is an indication of possible trouble. Infrared thermometers can be used to quickly check for hot bearings.

Question 5

Shaft run out can be measured with ________.

Answer 5

A dial indicator and a runout gage

Question 6

The seal in a compressor is necessary to prevent ________.

Answer 6

Refrigerant and oil from leaking out at the rotating shaft

Question 7

The mating seal surfaces on a sleeve type rotary bellows seal are ________.

Answer 7

Polished steel surfaces, and a carbon ring

It is the mating surfaces of the steel and carbon ring that formed a seal in this type of seal.

Question 8

A fan with a 14 inch sheave is connected by belts to a motor. Calculate the fan speed if the motor is operating at 1725 RPM, and is fitted with a 5 inch sheave. Use the formula below.

Answer 8

616 RPM

Question 9

With belt driven equipment, alignment of the motor and driven equipment pulleys _________.

Answer 9

** is accomplished using a string or straight edge.**

A straight edge or string can be used to run from one pulley to the other. Alignment is complete when the string or straight edge touches both pulleys in two places at once.

Question 10

To correct for soft foot, _________.

Answer 10

Shim under the high foot with shim stock, equal to a reading on the indicator.

The indicator is set up to read any movement as a mounting bolt is loosened. If loosening the bolt allows a foot to rise up, there is a soft foot condition, and shims must be added below the foot before the bolt is retightened.

Question 11

The two planes of alignment that must be considered when aligning a flexible coupling are _________.

Answer 11

Parallel, and angular

Shafts must be aligned, so that the center lines meet each other exactly in the center (parallel to one another or axially) and they must be aligned so that they have no angular difference between them (also called radial alignment)

Question 12

Electrical pressure is measured in_________.

Answer 12

Volts

Question 13

Electricity results from the movement of tiny negatively charged particles called_________.

Answer 13

Electrons

Question 14

Use the diagram below to answer the next question.

Calculate the voltage in the circuit when the total amperage is 10 amps and the resistors have values as follows: R1 = 10 ohms, R2 = 15 ohms,
R3 =20 ohms.

Answer 14

450 volts

Use ohms law to calculate the value for voltage in this series circuit. Remember that resistance is add up in a series circuit.
Rt= R1+R2+R3

Question 15

Use the diagram below to answer the following question.

Calculate the value for R3 when the value for R1 = 150 ohms, R2 = 500 ohms, the voltage is 120 V, and the amperage is 0.12 amps.

Answer 15

350 ohms

Use ohms law to calculate the value for resistance in this series circuit. Remember that ohms law will give total resistance. In this case, the volume for only one resistor is needed.

Question 16

Use the diagram below to answer the next question.

Calculate the voltage in the circuit when the total amperage is 20.4 A and the resistors have values as follows: R1=10 ohms, R2=50 ohms,
R3= 20 ohms.

Answer 16

120 volts

Use ohms law to calculate the value for voltage in this parallel circuit. Remember that in parallel circuits, current is additive, resistance is not.

Question 17

What is the maximum safe amperage draw of the secondary winding of a
60VA transformer output of 12 volts?

Answer 17

5 amps

Divide VA by volts to obtain the correct answer.

Question 18

The best way to determine the voltage requirements for an electrical component is to_________.

Answer 18

Read the nameplate data

Question 19

Fuses can be checked using a _________.

Answer 19

An ohm meter or a voltmeter

Question 20

Which of the following devices may be wired into the starting circuit of a single phase motor to improve the starting torque?

Answer 20

A start capacitor AND another winding

Question 21

A single phase motor with an improved power factor reduced motor current increased efficiency and high starting torque is the _________.

Answer 21

Capacitor start-capacitor run (CSR) motor

Because of the run and start capacitor, this motor offers the advantages listed above. The downside is additional cost.

Question 22

In a CSR motor with a 10 µF run capacitor and a 110 µF start capacitor, the total capacitance will be _________.

Answer 22

120 microfarads

The capacitance of capacitors, when wired in parallel as in a CSR motor are added together, the same as resistors in a series circuit.

Question 23

The instrument used for finding humidity levels in the atmosphere is a _________.

Answer 23

Sling psychrometer

This instrument provides both wet bulb and dry bulb readings that can be used with the psychrometric chart to determine the properties of the air just sampled.

Question 24

For reading the lowest vacuum levels, the best instrument to use is _________.

Answer 24

Electronic vacuum gauge

Electronic vacuum gauges are sufficiently accurate to measure pressures below 2000 µm.

Question 25

A hermetic motor should never be energized or tested with a megger when in a deep vacuum because _________.

Answer 25

The dielectric strength of the motors insulation would be greatly reduced.

Deep vacuums have the effect of greatly reducing the dielectric strength of a hermetic compressor motors insulation. Therefore, a hermetic compressor motor should never be energized, no matter how briefly, while it is in a deep vacuum. This would include performing a Megger test of the motors insulation while it is in a deep vacuum.

Question 26

What reduced voltage starter uses a switching arrangement to connect the windings of three phase motors in different configurations during start up and normal operation?

Answer 26

Star-delta starters

Star-delta starters connect the motor in a star (or wye) arrangement during startup, which reduces starting voltage to approximately 58% of line voltage. This limits starting current to about 1/3 that of what it would be if the windings were connected in Delta at start up. Once the motor has accelerated, the wiring configuration is switched to Delta and the motor continues to run under full voltage.

Question 27

According to NEC (National Electrical Code) a general use switch may be used as the controller for a stationary motor rated at 2 hp or less, and at 300 volts or less if it is rated at not less than_________.

Answer 27

Twice the full-load motor current

Question 28

Two types of thermal overload relays in common used today are _________.

Answer 28

** The bimetal relay, and the melting alloy relay**

Question 29

A rather common indication of a defective starting relay in a single phase motor is _________.

Answer 29

** The motor will hum but not start**

Question 30

The level of voltage caused by back electromotive force that opens the contacts on a potential relay in order to take the start capacitor out of the circuit is called _________.

Answer 30

Pick-up voltage

Question 31

A type of current relay that uses a bimetal strip to open contacts in both the starting and running contacts is called a _________.

Answer 31

hot-wire relay

Question 32

A pneumatic timing relay operates by _________.

Answer 32

** Filling a bellows with air**

When energized, a bellows fills with air, which takes time. The time can be adjusted by a needle valve, which regulates the rate at which the bellows fills. When fully expanded, the bellows operates a snap action switch.

Question 33

The combination safety limit and fan control on a residential furnace turns the fan on and off by sensing the furnace air temperature. If the furnace temperature rises too high, the safety limit de-energizes is the_________.

Answer 33

gas valve

The gas valve is shut off while the fan is allowed to continue running in order to cool the furnace.

Question 34

Some codes require a manual reset device on a safety limit __________.

Answer 34

** so that the cause of the safety shut down can be investigated prior to restart**

Question 35

In order to protect a load safety limit devices are most often wired _________.

Answer 35

in series

Series wiring de-energize the load when any one of several safeties trips.

Question 36

A flow switch safety control is used to_________.

Answer 36

** Prove that flow is occurring**

These switches prove that flow is occurring such as in water piping to hot water boilers to verify that the pumps are operating and water is flowing before the main gas valve is opened or to ensure that water is flowing through chiller barrels before energizing the compressor.

Question 37

What is a disadvantage of the mercury bulb switch?

Answer 37

They must be level

In order to operate correctly, the thermostat must be mounted absolutely level.

Question 38

A thermostat is properly calibrated when_________.

Answer 38

set point in control point are equal

Oh, setpoint refers to the manual setting of the thermostat while control point refers to the actual temperature of the space. The difference between the two is known as offset. When setpoint in control point are equal offset is zero, and the thermostat is said to be “satisfied”. If the temperature agrees with an accurate thermometer, it’s calibrated.

Question 39

With a change in temperature, a thermistor will change_________.

Answer 39

resistance

Question 40

One type of pressure sensing device uses a flattened metal tube which is bent into a part circle with one end fixed in place and connected to a system to be measured. The other end of the tube is closed and free to move. An increase in pressure tends to straighten the tube. The movement of the free end of the tube is connected to a dial that reads pressure. This type of gauge is called a_________.

Answer 40

Bourbon tube

Question 41

A pressure sensing device that relies on a fluid such as oil to provide a frictionless seal is the_________.

Answer 41

inverted bell

This device is suitable on only very low pressure, such as static pressure in an air duct, where pressures usually do not exceed several inches of water.

Question 42

An advantage of a diaphragm is that it can produce a large force when acted upon by only a small pressure. Calculate the total force exerted by an 8” diaphragm with a pressure of 1.8 psig applied to the diaphragm.

Answer 42

90.5 pounds

Force = Area x pressure
Area = π r²
F = π r² x psig
3.14 x 4² x 1.8 = 90.447 = 90.5 pounds

Question 43

The photocell in an infrared sensor is made of _________.

Answer 43

lead sulfide

Lead sulfide is a semiconductor having the property of decreasing in electrical resistance when exposed to radiation of certain wave lengths.

Question 44

Aiming of infrared sensors is critical. Why must they be aimed directly at the flame?

Answer 44

** Since they say heat, their sensitivity can be reduced by hot refractory**

The steady glow of a hot refractory will cause some decrease in resistance of the photocell material which reduces the sensitivity of the system. For this reason, the photocell should be installed so that it does not directly “see” the refractory.

Question 45

A type of two position control that provides for “intermediate” positions as well as the “all on” and “all off” positions is the _________.

Answer 45

floating control

Question 46

While proportional control action has the disadvantage of control point shift but has no time lag factor, floating action has the disadvantage of time lag influence but has no control point shift. What control action combined the advantages of both?

Answer 46

** Proportional integral**

PI control has no time lag factor and maintains a single control point.

Question 47

A flame sensing strategy that takes advantage of the fact that hot gases in a flame become ionized and conduct, electricity is called a _________.

Answer 47

flame rod

Flame rods are designed so that current conducted in the flame is much stronger in one direction (half cycle) than in the other, which produces a rectified signal.

Question 48

Checking amperage on a system during general maintenance _________.

Answer 48

can indicate a problem in the system

Amperage readings that are too high or too low can be an indication of electrical, mechanical or refrigerant charge problems with the system.

Question 49

When changing or adding oil to a compressor __________.

Answer 49

** it is best to buy the smallest possible containers and use the entire contents at once avoid pouring the oil from a container into the compressor and use an oil charging pump**

All of the above

Question 50

As the evaporating temperature of any vapor compression system is lowered,_________.

Answer 50

** Compressor capacity is lowered**

Question 51

As a “rule of thumb”, for every 12,000 BTUH of cooling capacity in an open compressor air conditioning system, the heat rejection is roughly _________.

Answer 51

15,000 BTUH, or 1.25 times the net refrigeration effect

Like any rule of thumb, this number can vary. However, as a basis for estimation, it has long been considered that the heat rejection from an air conditioning system is about 15,000 BTUH for every 12,000 BTUH of cooling capacity. This assumes open-type compressors, where the refrigerant suction vapor does not receive any heat from the compressor motor as it does in hermetic motor-compressors.

Question 52

The difference in temperature between condensing temperature and entering water or air temperature is known as _________.

Answer 52

temperature split

The condensing temperature should be at least 15° or 20° higher than the temperature of the entering water or air to avoid the need for an unreasonably large and costly condenser.

Question 53

A decrease in condensing temperature will _________.

Answer 53

Decrease condensing pressure, decrease suction, temperature, and increase system capacity

A decrease in condensing temperature affects the entire system, and will cause a drop in evaporator pressure. The drops in both condensing and evaporator pressures (and temperatures) result in a higher system capacity.

Question 54

Subcooling in the condenser will_________.

Answer 54

Increase system capacity

An increase in subcooling will increase the net refrigeration effect by reducing the flash gas loss.

Question 55

Compressor capacity controlled by the cylinder unloading method_________.

Answer 55

** may result in compressor overheating**

As fewer cylinders are used less refrigerant is pumped resulting in less refrigerant vapor available for cooling the compressor.

Question 56

10 in.Hg. Vacuum is approximately equivalent to __________.

Answer 56

10 psia

Absolute pressure is zero at a perfect vacuum of approximately 30 in. Hg. Meanwhile, atmospheric pressure is approximately 15 psia while vacuum is 0 in. Hg. The table below shows the relationship. Basically, every unit of five on the psia scale is equal to a unit of 10 on the vacuum scale. As vacuum increases by 10, pressure reduces by 5.

Question 57

After repairing a leak, it is permissible to pressure test a system using nitrogen with a small amount of _________ added as a trace gas.

Answer 57

HCFC 22

HCFC may be used as a trace gas when mixed with nitrogen for pressure testing, then vented into the atmosphere as it is not being used as a refrigerant.

Question 58

When charging a system, the refrigerant cylinder pressure may drop to low for further charging. Which of the following methods should not be used to increase the pressure?

Answer 58

** Heat the cylinder with a torch**

You should never heat a cylinder with a torch and should never raise the temperature above 125°F.

Question 59

A term used to rate vacuum pumps is used to describe the pumps ability to draw a vacuum. Essentially, the pump must create a vacuum within itself that is lower than in the system, so that gases will flow from the system to the pump. The point at which a pump can no longer create a pressure difference is called __________.

Answer 59

blank-off pressure

Question 60

Vacuum pump oil is a special oil because _________.

Answer 60

** it has a low vapor pressure to ensure that it won’t vaporize at low pressures.**

Question 61

Which of the following methods will not decrease the time needed to evacuate a large refrigeration system?

A. Using large diameter fittings
B. Keeping hose lengths as short as possible.
C. Triple evacuation.
D. Using multiple vacuum pumps.

Answer 61

Triple evacuation

Triple evacuation is a method that is no longer recommended since it vented refrigerant into the atmosphere. Further, it did not reduce evacuation time at all, but was a method used to dilute any contaminants within the system as much as possible.

Question 62

A danger with leaving a vacuum pump running all night is ___________.

Answer 62

** Exceeding the pumps running time capabilities and pump oil could be lost during a power outage**

Question 63

Vacuum pump oil that is fresh _________.

Answer 63

has a clear appearance

New oil has a clean and clear appearance. If it looks otherwise, it should be changed.

Question 64

A refillable refrigerant cylinder must not be filled above ________ percent of its capacity buy weight.

Answer 64

** 80%**

Question 65

A refrigerant with the ANSI/ASHRAE standard 34–1992 safety classification of A1 has__________.

Answer 65

** Low toxicity, and no flame propagation**

Question 66

All appliances containing more than 50 pounds of refrigerant (except commercial and industrial process refrigeration) must be repaired when the annual leak rate exceeds_________.

Answer 66

15%

EPA requires that all appliances containing more than 50 pounds of refrigerant except commercial and industrial process refrigeration must be repaired when the annual leak rate exceeds 15% and commercial and industrial process refrigeration must be repaired when the annual leak rate exceeds 35%.

Question 67

When charging a chilled water system charging is usually done as a liquid. However, if the machine is in a deep vacuum, the initial charge should be as a vapor. Why?

Answer 67

** Charging as a vapor until the system temperature has risen above 32°F prevents freezing of water in the tubes**

The system must be charged as a vapor until the system pressure has reached a pressure corresponding to a temperature higher than 32°F.

Question 68

When charging a system, several methods are available for checking the refrigerant charge in order to charge by monitoring the sub cooling one must_________.

Answer 68

** Monitor discharge pressure and liquid line temperature close to the metering device and charge until the liquid line temperature falls below the discharge saturation temperature by the expected amount of subcooling**

Question 69

Insufficient refrigerant will cause_________.

Answer 69

** Low suction, pressure and insufficient cooling**

Question 70

Most compressors are positive displacement machines. Name a compressor that is not a positive displacement machine.

Answer 70

Centrifugal

Question 71

The ratio of the actual volume of refrigerant vapor pump to the theoretical displacement, volume is known as_________.

Answer 71

** volumetric efficiency**

Question 72

A compressor in which the compressor and motor are both sealed within the same pressurized housing is known as a_________.

Answer 72

** Hermetic compressor**

Question 73

The passage of liquid refrigerant through the compressor suction and discharge valve should be avoided and is known as_________.

Answer 73

** Slugging the compressor**

Question 74

Modern high-speed, reciprocating compressor is typically operate a_________.

Answer 74

1750 and 3450 rpm

Question 75

Compressor capacity decreases as_________.

Answer 75

Discharge pressure increases, suction pressure decreases, and compressor speed decreases.

Question 76

And advantage of the scroll compressor is_________.

Answer 76

** Smooth, quiet operation, low torque variation through overlapping compression cycles, and few moving parts**

Question 77

How can you identify reverse operation with a scroll compressor?

Answer 77

** the compressor will not compress, and the compressor will stop on motor overload**

Question 78

During scroll compression_________.

Answer 78

** Refrigerant vapor enters from the outside of the scroll and exits at the center**

Question 79

Capacity control on a helical-rotary (screw) compressor is obtained using_________.

Answer 79

** a sliding valve**

Question 80

The screw type impellers used in helical rotary compressors are also known as_________.

Answer 80

** rotors**

Question 81

The component in a centrifugal compressor that actually does decompressing is known as_________.

Answer 81

** an impeller**

Question 82

A centrifugal compressor controls capacity through the use of_________.

Answer 82

** Variable speed, and vortex dampers**

Question 83

Bearings in a centrifugal compressor can be checked by_________.

Answer 83

Checking the temperature of the oil returning from the bearing

A high temperature in the oil indicates a bearing with a large amount of friction, indicating that a problem exists.

Question 84

A small access valve, which is similar to the air valve used on tires is known as a_________.

Answer 84

** Schrader valve**

Question 85

A valve used to prevent flow of liquid, refrigerant to the evaporator and to avoid flood back to the compressor during off cycles is_________.

Answer 85

** solenoid valve**

Solenoid valves have many applications in refrigeration systems, the principal one being to prevent flow of liquid, refrigerant to the evaporator, and to avoid flood back to the compressor during off cycles.

Question 86

Hey special valve used to prevent evaporator temperature from falling below a predetermined minimum temperature regardless of suction pressure is the _________.

Answer 86

** evaporator pressure regulator**

An example of an application for this valve is on systems with multiple evaporator’s operating at different temperatures.

Question 87

A metering device with the characteristic of feeding liquid into the evaporator at the same rate at which the liquid flows from the condenser is the_________.

Answer 87

** High side float valve**

This valve consists of a float and a needle valve, which creates the pressure drop separating the high side from the low side of the system. As the liquid level from the condenser raises, the float raises and opens the needle valve, forcing refrigerant into the evaporator. As the liquid level from the condenser drops, the float drops also and closes the needle valve restricting the flow to the evaporator.

Question 88

In a thermostatic expansion valve, three forces act on the diaphragm in the powerhead, which is connected to the valve. Evaporator pressure acts to_________ the valve, spring pressure acts to_________the valve, and bulb pressure from the bulb attached to the evaporator outlet asked to blank the valve.

Answer 88

Close; Close; Open

Both the evaporator pressure and the spring pressure act to close the valve while the suction pressure from the bulb asked to open the valve.

Question 89

The metering device that actually measures temperature rather than pressure or liquid levels_________.

Answer 89

** thermal electric valve**

Question 90

Suction line filter driers should be installed whenever_________.

Answer 90

** a hermetic compressor motor burn out has occurred**

Suction line filter driers should be installed whenever a hermetic compressor motor burn out has occurred to filter out debris and carbon char and to neutralize system acid, which is usually generated.

Question 91

Filter, dryers and dryers are filled with the material that is able to catch and retain moisture and acid. This material is called___________.

Answer 91

Desiccant

Question 92

Suction line filter dryers are usually equipped with Gage connections, so that pressure drops can be determined. Why?

Answer 92

So that you can determine when to change the filter drier

Manufacturers publish tables that specify permissible core pressure drops. When the drop exceeds recommendations, the core should be replaced.

Question 93

In general, the greater number of rows in an evaporator_________.

Answer 93

** The more closely the leaving air temperature will be to that of the refrigerant, the more dehumidification can take place, and the colder the leaving air will be.**

Question 94

Increasing airflow over in evaporator__________.

Answer 94

** increases evaporator capacity**

The more air that flows past in evaporator, the more energy is absorbed by the refrigerant. Using the formula for sensible heat transfer, it can be seen that if the temperature difference between the air and the refrigerant remains the same, an increase in airflow (CFM) will result in an increase of energy transfer (BTUH).
Btuh = cfm x 1.08 x ΔT

Question 95

Capacity control of a lithium bromide water absorption machine is accomplished__________.

Answer 95

By controlling the heat input to the generator

More heat results in an increased amount of refrigerant boiled out of the solution in the generator, creating more refrigeration effect. Less heat results in less refrigeration effect.

Question 96

Crystallization may occur in a lithium, bromide water absorption__________.

Answer 96

** if power fails while the machine is under a heavy load, if condenser water is allowed to get too cold, and if the machine over cools during a shut down**

Question 97

The heat source for absorption liquid chillers could be_________.

Answer 97

** solar panels, steam, or hot water**

Question 98

The purge units on absorption liquid chillers are designed to_________.

Answer 98

** expel noncondensible gases**

Question 99

A possible cause for high head pressure is_________.

Answer 99

** dirty condenser tubes, insufficient water flow through the condenser, and air or noncondensibles in the condenser**

Question 100

Approach temperature is the difference_________.

Answer 100

** Condensing temperature and leaving water temperature**

Calculate approach, temperature by subtracting the living water temperature from the condensing temperature.

Example: 105°F condensing temp - 95°F leaving water temp = 10°F approach temperature.

Question 101

Calculate the amount of water needed per ton of refrigeration in a water cooled condenser assuming a heat rejection rate of 15,000 BTUH per ton and a 20°F water temperature rise through the condenser.

Answer 101

1.5 gpm

GPM = Btuh ÷ (Δt x 500)

Question 102

What are the three ingredients necessary to start in sustain combustion?

Answer 102

fuel, oxygen, and heat

Question 103

What are the products of perfect combustion using oxygen and a hydrocarbon fuel?

Answer 103

Carbon dioxide, heat, and water

Perfect combustion produces only heat carbon dioxide and water (in the form of vapor)

Question 104

Describe the appearance of a properly adjusted natural gas flame in an atmospheric burner.

Answer 104

Steady blue flame with a smaller lighter blue inner cone resting on the burner port

Question 105

Radiant tubing/piping should be pressure tested to at least ______ times the expected operating pressure.

Answer 105

2

Question 106

When filling a radiant heating system, it is recommended to fill__________.

Answer 106

** Slowly from the low point, so that the tendency for air pockets to form is reduced**

The idea is to add the water slowly so that air is “chased” to the top of the system so that air pockets do not form.

Question 107

Infrared heaters use burning gas to heat a specific radiating surface instead of using the infrared energy from the open flame because_______.

Answer 107

** heated surfaces are better heat radiators an open flame**

Question 108

High efficiency (condensing) furnaces achieve an efficiency of up to 95% by_________.

Answer 108

** Cooling the exhaust gases to below dewpoint and recovering some of the latent heat of condensation**

High-efficiency condensing furnaces cool exhaust gases to below 130°F. This temperature is below the dewpoint and gains of an additional 1000 BTU for every pound of water condensed is realized. The exhaust gases are cooled to the point where they will not rise up the vent on their own, so an induced forced draft fan must be added. Further, a drain must be installed to take away the condensed water from the exhaust gases.

Question 109

Calculate the efficiency of a furnace with a 95,000 BTUH input burner that produces 76,000 of usable heat.

Answer 109

80%

Efficiency = output ÷ input

Question 110

Safety controls on a high-efficiency condensing furnace include________.

Answer 110

** high limit, flame proving, door switch, and induced draft pressure switch**

In order for a high-efficiency condensing furnace to operate, these for safety devices must be “made”

Question 111

The purpose of a boiler low limit control is to__________.

Answer 111

** Start the boiler, when boiler water temperature drops below a certain value**

The low limit maintains boiler water temperature even when the thermostat is not calling for heat. This feature is necessary when using the boiler to heat domestic hot water.

Question 112

In order for fuel oil, to be burned, it must be itemized. This is done by forcing it through a nozzle under a pressure of__________.

Answer 112

100 psi

Question 113

A method of sensing flame in older style fuel oil furnaces and boilers was the stack switch which sensed heat in the stack. This required the fuel to ignite, then heat the stack. A trial for ignition took up to 90 seconds. A newer and quicker safety control that “sees” the bright yellow flame has all but replaced the stack switch in fuel oil burners. What is this photocell safety control?

Answer 113

** a cad cell using cadmium sulfide as the sensor**

Cadmium sulfide is used as a photocell in a visible light detector. It has the property of offering low resistance when exposed to light and high resistance when there is no light. Cad cells work well with a fuel oil flame because it is bright yellow. Natural gas and propane burn with a blue colored flame and do not produce much light so cad cells do not work well with those fuels.

Question 114

The practice of adjusting boiler water temperature so that water temperature is hottest on the coldest days and coolest on warmer days is known as _________.

Answer 114

Outdoor reset

Question 115

A compression tank is provided in a hydronic system_________.

Answer 115

** so that higher pressures can be built up, thereby raising the boiling point, so that room is provided for heating water to expand, and to provide a cushion against sudden pressure changes and waterhammer shock.**

Question 116

Expansion joints are needed in hydronic system__________.

Answer 116

** to allow for expansion and contraction of the piping**

Copper tubing expands 1.66” per hundred feet with a 150°F temperature rise. Steel expands 1.17”under the same conditions. Allowances must be made for this movement or leaks will develop and pipes/fittings may crack.

Question 117

In order to reduce water turbulence at the suction end of a pump, a suction diffuser should be used or a length of straight pipe equal to_______ times the diameter of the pipe.

Answer 117

** 5 **

Question 118

Premature bearing we’re on the floor mounted palms could be caused by__________.

Answer 118

** suction, or discharge lines that were forced into position when the pump was installed**

The torque of the pipes on the bearings causes excessive stress and could easily lead to early bearing failure.

Question 119

Hey, stuffing box type of shaft, seal on a centrifugal pump need periodic maintenance. If the seal is found to be leaking excessively, the technician should ________.

Answer 119

** Tighten the packing gland and/or replace the packing**

In most cases, simply tightening the packing gland will minimize the leakage. Remember that this type of seal is designed to leak slightly as the water acts as a lubricant. If tightening the packing gland does not minimize the leak, the packing itself may be worn and need replacing.

Question 120

Cavitation can destroy a centrifugal pump, is noisy and is caused by________.

Answer 120

** Inlet pressure that is too low**

Inlet pressure that falls below the manufacturer’s recommended net positive suction head (NPSH) will cause water to boil due to the low pressure, causing bubbles and cavitation.

Question 121

The vacuum pump used in vacuum steam heating systems that creates a vacuum using high velocity water is the__________.

Answer 121

** jet type pump**

The jet pump forces water through an injector that increases its velocity, creating a correspondingly low pressure around it, creating a suction that causes water to flow.

Question 122

Vacuum pumps used in vacuum steam heating systems can be destroyed if they are made to pump_________.

Answer 122

** air and steam**

Both air and steam can destroy a vacuum pump. However, through the design of vacuum steam heating vacuum pumps, air typically does not enter the pump. The intake of these pumps draw from a tank that is vented to the atmosphere. The vent is to allow air to escape. The pump intake is near the bottom of the tank, so only water is drawn into the pump. Further, pump cavitation is caused by low suction pressure. Since the intake of the pump is connected to a tank under atmospheric pressure, the pump does not see low suction pressures. Steam can reach the pump, However, if the steam traps allow live steam to blow by and enter the condensate lines.

Question 123

If a vacuum pump in a vacuum steam, heating system burns out a very common cause is________.

Answer 123

** a failed steam trap**

A failed steam trap will allow live steam to blow by. If the steam makes it to the vacuum pump, it can destroy the pump. In buildings with many steam traps and poor maintenance procedures, failed steam traps are a common cause of vacuum pump failure.

Question 124

The type of pump found in a fuel oil burner is the__________.

Answer 124

** gear pump**

Question 125

A gear pump is a type of__________.

Answer 125

** rotary pump**

Question 126

Effective recovery of condensate reduces the following cost of making steam:

Answer 126

** fuel and energy cost associated with producing steam, boiler water make up and sewage treatment, boiler water chemical treatment.**

Question 127

A symptom of a failed steam trap________.

Answer 127

** a track that is warmer than condensate temperature**

A trap that is warmer than condensate temperature indicates that steam is flowing freely through it, meaning that the trap is not trapping the steam as it is designed to do.

Question 128

After the first heating season, cleaning a dirt pocket by removing the cap on the bottom of a dirt pocket__________.

Answer 128

** is usually not required**

The dirt pocket should be clean several times during the first heating season to remove heavy foreign materials such as scale and pipe cuttings. Thereafter, such attention is usually not required.

Question 129

The average house line pressure for natural gas is_________.

Answer 129

7” W.C.

Question 130

The pressure is measured on a residential gas regulator using a_________.

Answer 130

** Water manometer**

A water manometer provides a cheap and accurate way to measure the low pressures encountered in residential gas systems. Gas valves report pressure settings in inches of water column, which is read with the water manometer.

Question 131

The purpose of the gas regulator vent is to__________.

Answer 131

** allow air to enter above the diaphragm, allow air to escape above the diaphragm, and allow gas to escape if the diaphragm ruptures.**

Question 132

An advantage of the inverted bucket trap is that_________.

Answer 132

** it also vent air and carbon dioxide continuously at steam pressure**

During operation, steam, air and CO2 rise to the top of the inverted bucket. The steam condenses, but the air and CO2 remain a gas. When the valve at the top of the trap opens, the air and CO2 are the first to leave the trap.

Question 133

Flash theme is caused by_________.

Answer 133

** pipe friction, reduced pressure, And a vertical rise in a condensate line**

Question 134

The purpose of a drip leg in a steam line is to_________.

Answer 134

** let condensate escape by gravity from the fast-moving steam, and store condensate until it can be discharged through the steam trap.**

Question 135

In adequate trapping of steam means often leads to_________.

Answer 135

** water hammer and damaging slugs of condensate**

Steam and condensate flowing in the same pipe can cause water hammer and in severe cases, actually destroy piping components leading to the discharge of live steam into the atmosphere.

Question 136

Pressure in a vertical condensate pipe will drop 1 psi for every _______ feet in elevation. This is an important factor since boiling temperature drops as pressure drops. When elevating condensate this drop in pressure can cause flash steam.

Answer 136

2.31

2.31 feet of head is equal to 1 psi. This is the same factor used in pumping calculations.

Question 137

When using a listening device to test a steam trap, what will the technician listen for that could indicate a problem?

Answer 137

** high velocity sound**

Escaping steam will have a higher velocity sound than normal operation of the trap, be it continuous or intermittent. An electronic listening device can be used for this, although a simple screwdriver, with one end held against the trap and the other against your ear, works just as well. In either case, experience is required to distinguish between sounds of the trap and other sounds in the system.

Question 138

If an inverted bucket steam trap is blowing live steam. What might the trouble be?

Answer 138

** the valve may have failed to seat because of wear or a piece of dirt or scale, the trap may have lost its prime, or the bucket is stuck or has a hole in it**

Question 139

The__________ drains the condensate from the steam header and returns it to the boiler below the water line while preventing the boiler water from flowing out of the boiler into the return main.

Answer 139

** equalizing line**

The water level in the equalizing line is the same as in the boiler, because the steam pressure on the top of both lines is the same. This prevents the boiler water from flowing out of the boiler into the return main.

Question 140

The__________ is designed to protect boilers against the loss of water do to leaks in the wet return line.

Answer 140

** Hartford loop**

The Hartford loop prevents water from dropping more than 2” to 4” below the normal operating water line (NOWL) through the condensate wet return line by breaking the siphoning effect once the water reaches that level.

Question 141

The control valve in a
sub-atmospheric steam heating system is limited to approximately ______% change per minute.

Answer 141

3

The control valve is designed with a small percentage of change so there are no radical changes in the pressure and steam temperature in the system piping.

Question 142

A vacuum breaker is installed between equipment and a steam trap to_________.

Answer 142

** Allow condensate to drain after the steam has been shut off**

Once the steam supply has been shut off, steam will condense and will be unable to drain because of the vacuum. The vacuum breaker provides a vent and allows the condensate to drain.

Question 143

The most commonly used inspection used on fans and air handling equipment is___________.

Answer 143

** visual**

There is nothing like a good old walk around. An experienced technician can spot trouble without needing expensive equipment, although specialized equipment can confirm that a problem exists.

Question 144

Which air distribution system includes both warm air duct and cool air duct and utilizes mixing boxes near the zone to mix the cool air and warm airstreams to achieve the desired temperature while delivering the air at a near constant volume?

Answer 144

** dual duct**

Question 145

Which duct system delivers constant temperature air at variable volumes?

Answer 145

VAV

Question 146

When soldering, solder is drawn into the joint by_________.

Answer 146

** capillary action**

Capillary action is the flow of a liquid when it is drawn into a small space between wetted surfaces. This is the same action that draws colored water into flowers during biology experiments and allows trees to get water from the roots to the crown.

Question 147

Which of the following best describes the difference between brazing and welding?

A. Welding is an adhesive process while brazing is cohesive.

B. Welding is a cohesive process while brazing is adhesive.

C. Brazing is done on non-ferrous metals. Welding is done on ferrous metals.

D. Both B and C.

Answer 147

** B. Welding is a cohesive process while brazing is adhesive.**

Question 148

The practice of installing flanges on pipe and fittings, so that the top bolt hole in the right hand and left hand section of the flange are level with each other is known as_________.

Answer 148

Two-holing

This practice makes leveling of fittings and piping easy. The bolt holes in the flanges on flange fittings and valves are drilled according to this rule.

Question 149

Of the valves listed below, which provides the best throttling action

A. Ball valve
B. Globe valve
C. Gate valve
D. Plug valve

Answer 149

** Globe valve**

The flow through a globe valve changes course through two 90° turns causing increased resistance to flow and sometimes a considerable pressure drop.

Question 150

A rating of 125 lb S – 200 lb W.O.G. stamped on a valve means that the valve__________.

Answer 150

** Has a steam rating of 125 psi and a cold water/oil/gas rating of 200 psi**

This rating means the valve can be used with steam up to 125 psi, provided that the temperature does not exceed the value established by the manufacturer. It can also be used with cold water, oil or gas up to 200 psi at ambient temperatures.

Question 151

A device designed to protect pipe insulation against damage because of pipe movement is called a__________.

Answer 151

** pipe saddle**

Question 152

Safe Working Load(SWF)

The safe, working load of a fiber or wire rope can be calculated using the formula:

Breaking Strength(BS)
÷
Safety Factor(SF)

where the safety factor for hoisting material is required by OSHA to be______.

Answer 152

5

This means that a rope with a breaking strength of 10,000 pounds can safely lift 2000 pounds.

Question 153

Calculate the amount of weight that could be lifted if a force of 100 pounds is exerted in the direction of the arrow.

Answer 153

300 pounds

There are three ropes supporting the load in the drawing. Multiplying the force exerted by the number of supporting ropes results in the amount of weight that can be lifted.

Question 154

The weakest portion of a chain hoist is the_________.

Answer 154

** lower hook**

The lower hook is designed to spread when overloaded. The inner contour of the load hook is an arc of a circle and any deviation from this circle is evidence of overloading.

Question 155

An overload of most cable hoist (come-alongs) is prevented__________.

Answer 155

** by a handle that bends**

The manufacturer designs the lever handle to bend before an unsafe load can be lifted. This handle should not be replaced with a stronger bar, nor should cheater devices be used, as both practices will bypass the safety feature.

Question 156

When using a jack to lift a load__________.

Answer 156

** chocks should be used, use wooden softeners, and do not place the jack directly on the ground.**

Question 157

Unless equipped with OSHA or Canadian standards association (CSA) approved ground fault circuit interrupters, portable electric lighting used in wet and/or other conductive locations as for example, drums, tanks and vessels, shall be operated at_____volts or less.

Answer 157

12

Question 158

A ladder must extend above the edge of a roof by at least___________.

Answer 158

Three feet

Question 159

The proper angle for a ladder is achieved when the distance of the ladder from the building at the base is about_______ the working length (height) of the ladder.

Answer 159

One fourth

Question 160

A lock and tag may only be removed by the employee that applied it unless the employee is absent from the workplace, then the lock or tag may be removed by a qualified person designated by the employer to perform this task provided that the employer ensures that__________.

Answer 160

** The employee who applied the lock or tag is not available at the workplace and the employee who applied the lock or tag is aware that it has been removed before he, or she resumes work at that workplace**

Question 161

Section 608 of the Clean Air Act prohibits you from knowingly venting ozone depleting compounds used as refrigerants into the atmosphere while maintaining, servicing, repairing, or disposing of air conditioning or refrigeration equipment (appliances). The date when this prohibition took affect is __________.

Answer 161

July 1st, 1992

Question 162

When working on a HCFC-22 appliance or isolated component of such appliance, normally containing 200 pounds or more of refrigerant and using recovery or recycling equipment manufactured or imported on or after November 15, 1993, you are required to evacuate to a level of_________.

Answer 162

10 in. Hg

Question 163

If a compressor burnout has occurred, the refrigerant must be__________.

Answer 163

** Recovered and reclaimed**

Question 164

Plot a system curve on the fan curve chart below. Use an operating point of 8000 CFM at a static pressure of 4 in. water column as a basis for your calculations. What will the static pressure be at 7000 CFM?

Answer 164

** 3 in. water column**

Using the formula in the first figure below yields a static pressure of 3.06 in. water column. Plotting the system curve on the figure above shows an operating point at the intersection of the fan and system curves.

Question 165

Calculate the volume in gallons of a cylindrical tank, having a base diameter of 46” and a height of 70”. use the formula in the picture below.

Answer 165

504 gallons

23² x 70 x 3.14 = 116,333.175 gallons

116,333.175 ÷ 231cu.in. = 503.6

rounded up = 504 gallons

Question 166

Calculate the velocity of air measured in feet per minute (FPM) in a 36” x 32” duct with 48,000 CFM of airflow. Use the formula below but remember that all units must be in feet.

Answer 166

6000 FPM

Area = 36” x 32” ÷ 144 (converting
sq. In. to sq. ft.)

36 x 32 ÷ 144 = 8

48,000 ÷ 8 = 6000 FPM

Question 167

The symbol in the figure below would be used to indicate a ________ switch that ________ on a rising signal.

Answer 167

Pressure, Closes

Question 168

The symbol in the figure below represents a__________.

Answer 168

Thermopile

Question 169

The circuit in the figure below represents a___________.

Answer 169

Current Relay