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WorksheetsHeat Pump Prep Test
Total questions: 100
Worksheet time: 51mins
An air-to-air heat pump has many of the same components as an air conditioning system. The major difference is that a heat pump also has a
evaporator
condenser
reversing valve
thermostatic valve
What is the difference between "demand defrost" and "timed defrost?"
Demand defrost depends on a manual action, and timed defrost depends on how cold it is outside
Demand defrost senses temperature difference across the coil, and timed defrost is signaled by the time clock
Demand defrost depends on a low-pressure control and timed defrost has and electric defrost heater
Demand defrost happens only when needed and timed defrost is based on time/temperature.
The thermostat that controls the auxiliary electric heat according to the outdoor temperature is called
auxiliary temperature control
outdoor auxiliary thermostat
outdoor ambient thermostat
hold in thermostat
The outdoor temperature at which the heat pump provides the same amount of heat as the heat loss of the conditioned space without auxiliary heat is known as
initial balance point
second balance point
initial capacity point
initial efficiency point
At what temperature is an outdoor ambient thermostat normally set
At 32 degrees Fahrenheit
Slightly above the initial balance point
The same as the indoor thermostat
15 degrees above the initial balance point
the outdoor coil is frozen solid on a "no heat" service call. The most likely reason is
the indoor fan is inoperative
the unit is overcharged
the unit is functioning on Auxiliary heat
the outdoor fan is inoperative
in order to determine a heat pump's balance point, you must first calculate
The building's heat load
the consumption of kilowatts at 32 degrees
the EER of the unit during a particular season
the brand name of the compressor
when a heat pump is used for heating and cooling, the system is sized by the
heating load
cooling load
heating and cooling load combined
difference between the heating and cooling load
a high efficiency heat pump system designed to function from high to low ambient conditions below 10F, may have?
two outdoor coils with each one incorporating a dual stage compressor
two indoor coils with parallel metering devices
an auxiliary heat exchanger injected with an ethylene glycol solution
two compressors which operate in series
Room thermostats for heat pump should be installed
as far away from the main return air grill as possible
as near to the main return air grill as possible
on an outside (cold) wall
near an exit door or near a window
when the heat pump compressor has malfunctioned, the customer has the option to switch the system into
auxiliary heat mode
emergency heat mode
1st stage heat mode
2nd stage heat mode
Start-up with a night set back digital thermostat requires the technician to always
set the secondary heat anticipator
set the primary heat anticipator
de-energize the thermostat to protect the circuit, until the customer is proficient in its use
teach the customer how to program the thermostats
the heat pump defrost board can be manipulated by the technician to
troubleshoot system pressures
program the thermostat
simulate the defrost cycle
reverse fan rotation
the air-to-air heat pump outdoor unit is most efficient if located
In a cold climate
toward the prevailing wind
in a confined area
in a moderate climate zone
which of the following are innovations that may be found on new high efficiency units?
Electric defrost systems
Higher compression ratio
Automatic pump-down
ECM fan motors
How may a lockout (impedance) relay be reset?
just push the reset button. They are all manual reset
the technician has to fix the unit before reset
simply disconnect power to the unit momentarily
the lockout relay automatically resets after 15 minutes
the temperature difference between the 1st and 2nd bulbs for heating on a heat pump thermostats is
dependent on ambient temperature
26° F, if the ambient temperature is not known
approximately 2° F
there is no temperature difference
SEER is calculated by
The Seasonal Energy Efficiency Ratio
Dividing the BTUs removed by the watts consumed during the cooling season
How highly efficient the unit is verses cost of the unit
Heat produced divided by voltage rating on the compressor
If the indoor fan is operated at an excessive speed in the cooling mode;
the system will not properly remove the humidity from the conditioned space
the system not get the conditioned space cool enough
the second stages of the thermostat can override the first stage
the outdoor coil may become frosted
the most preferred method of charging any system in the field is
vapor into the suction line (unless it's a blend)
liquid into the suction line if it is a blend
by weight
superheat and subcooling
what is the industry standard for deep vacuum?
pump it down for 3 hours
triple evacuate with nitrogen
maintain 500 microns for 15 minutes
maintain 200 microns for 10 minutes
Good service practice for installation of a reversing valve includes;
use a hacksaw to remove the old valve
use lock pliers to hold the new valve body while brazing
to prevent oxidation wile brazing, purge the system with refrigerant
use heat paste and wet rags while brazing in the new valve
off-cycle crankcase heat is provided by;
one leg of supply voltage is directed through the start winding
a dual run capacitor, which allows a small amount of current to pass through the windings
a small amount of current is passed through the start capacitor to heat the start winding
the crankcase heater is wired to an intermittent timer
You are checking for in CFM on a three ton heat pump system. The system has one return grill measuring 24"x 24", which has a net free area of 3.4 square feet. You measure air velocity and calculate an average of 400 FPM. From this information you can conclude that;
airflow in CFM is above normal range
airflow in CFM is within normal range
airflow in CFM is below normal range
this is not enough information to calculate airflow
what control operates the 1st stage of secondary heat?
the 1st outdoor thermostat
the peak hours of power consumption in your area
the second heating stage of the indoor thermostat
high fire on the gas valve
what is the industry standard for maximum duration for defrost?
as long as it takes to get the ice off the coil
15 minutes if it's hard ice
a maximum of 10 minutes
a maximum of 30 minutes
what is the recommended CFM across the evaporator coil of a heat pump?
600 to 700 CFM
400 to 450 CFM
200 to 300 CFM
150 to 225 CFM
if manufacturers specifications are not available, a good way to calculate cubic feet per minute through a coil is to:
use temperature rise on emergency heat mode
assume 400 CFM per minute for all heat pumps
multiply the horsepower of the moto times the sq. circumference of the blower wheel
use temperature rise in emergency cooling mode
What type of defrost is employed on this heat pump?
pressure-time initiation, temperature termination
time and temperature initiation, time or temperature termination
time or temperature initiation, time and temperature termination
pressure initiation, temperature termination
which component is responsible for energizing auxiliary heat during the defrost cycle?
the defrost time clock
the reversing valve relay
heater relay-1
The defrost relay.
When this unit switches to the heat mode, describe the sequence of events that take place.
the RVR coil is energized through TH-1. The CR coil is energized through the RVR contacts.
the reversing valve relay is de-energized by N.C contacts of the DFR, and HR-2 is energized through ODT-2
the CR N.O, contacts close energizing the C coil, which in turn sends the hot gas into the indoor coil and meters liquid to the outdoor
the CR N.C, contacts close energizing the C coil, which in turn sends the hot gas into the indoor coil and meters liquid to the outdoor
The DTC motor and cam will close the DTC N.O. Contacts momentarily (approx. 5 seconds). How is the DFR kept energized when the DTC N.O contacts open?
the RVR contacts will be closed in the heating mode, which keep it energized
the DFR N.C. contacts close during defrost and the DFR N.C. contacts open
the DFR N.O. contacts close , which forms a holding circuit .
it is specially designed impedance coil in the circuit that keeps the coil energized
How is defrost terminated in this system
the air pressure sensor contacts open, indicating the coil is defrosted
the defrost thermostat is warm enough to open, normally 35° F or below
the defrost time clock has clock has closed the circuit after 20 minutes of defrost
either the time or temperature termination requirements has been satisfied
Where is the LLP physically tapped into the system on this heat pump?
on the suction line before the reversing valve
on whichever line is the suction in the cooling mode
on the liquid line before the reversing valve
on the bi-flow liquid line located between the two coils
You are starting-up a split system heat pump for the first time. The outdoor ambient temperature is 60 ° F . You check the temperature split across the indoor coil in the heat mode and find it is 38°F. You switch to cooling mode and determine a temperature split of 29°F. The most likely corrective action (relative to airflow) is;
lower the indoor fan speed
decrease the outdoor fan speed
increase the outdoor fan speed
increase the indoor fan speed
Heat pump heating mode efficiency is rated in;
BTUs
HSPF
AFUE
SEER
on a water source heat pump, the heat mode water regulating valve must be
2 way
3 way
direct acting
reverse acting
An R410A heat pump operating in the heating mode has a suction pressure 50 psig and had pressure of 285 psig has a compression ratio of;
4.6:1
3.2:1
5.7:1
7.7:1
which type of heat pump does not require a defrost cycle?
air to air
PTAC
window unit
water source
An R-22 heat pump operating in the cooling mode has a suction pressure of 68 psig. Adding 2 psig for pressure drop in the coil, the true The temperature of the suction line at the outlet of the evaporator is 53° F outlet pressure is 70 psig. What is the superheat?
43 degrees
24 degrees
19 degrees
12 degrees
On a time initiation/temperature termination defrost, the defrost time clock has one N.O. and one N.C.: switch. When do the positions of these switches change?
every time the defrost timer energized
every 30 to 90 minutes, depending on the cam installed in the timer
when the pressure switch senses a blocked coil
ever hour, depending on the time of day
What would be the result of closing registers in room that are uninhabited while operating in the heating mode?
the total airflow will increase, making some occupied areas warm
the suction pressure will drop and the temperature will rise decreasing life spam of the unit
you will save on energy costs due to the decreased load on the compressor
The discharge pressure and temperature will rise decreasing the life span of the unit
What is the most common complaint from a customer changing from gas heat to heat pump?
cold air at high velocities coming out of the registers
the lights on the thermostat are distracting
low side wall registers
really cold condenser air
When a heat pump is operating in the heat mode, the suction line at the compressor will feel;
luke warm
hot
near ambient temperature
cold and sweaty
The use of a scroll type compressor on a heat pump can eliminate the need for a;
reversing valve
charge compensator
defrost cycle
suction line accumulator
A heat pump operates satisfactorily in the cooling mode, but not in the heat mode. This could be caused by;
a fan not operating properly
low outdoor temperature
high outdoor temperature
a stuck check valve or clogged TXV screen
It is not always a good idea to immediately connect a standard gauge manifold set and hoses to a heat pump when a problem is suspected because;
most technicians cannot read a gauge properly
gauges are never accurate
the charge is critical, sometimes plus/minus 1/2 oz. refrigerant
a gauge manifold set is very expensive and should be used sparingly
Which component is responsible for changing the direction of the flow of refrigerant?
thermostatic expansion valve
capillary tube
reversing valve
check valve
Some heat pump system use a ___________ as a metering device
AEV / capillary tube
low side float
inverted flow control
fixed orifice
The slide valve and piston in the reversing valve is actuated by pressure directed through the;
solenoid and pilot valve
defrost thermostat
defrost timer
outdoor thermostat
During the heating cycle, the outdoor coil is used as;
the condenser
the evaporator
a receiver
an accumulator
During the cooling cycle, the indoor coil becomes;
the condenser
the evaporator
a receiver
an accumulator
During the defrost cycle, the outdoor fan is usually;
set to high speed
set to slow speed
turned off
run in reverse
Heat pump systems which use a thermostatic expansion valve at each coil will also have;
a by-pass lines with check valve
a capillary tube parallel to the liquid line
the TXV sensor bulb connected to the liquid line
pressure switch for each TXV
Refrigerant flow though the compressor;
is normal in the heat mode and reversed in the cool mode
is normal in the cool mode and reversed in the heat mode
is always the same regardless of operating mode
can be either direction depending on operating mode
Because of the possibility of liquid flood-back, a heat pump that uses a reciprocating compressor should be equipped with a;
suction receiver
crankcase pressure valve
liquid receiver
suction accumulator
A scroll type compressor;
is more susceptible to damage from liquid flood-back
is less susceptible to damage from liquid flood-back
can be operated in either direction, which makes it well suited for heat pumps
is not suited to heat pump applications
On a split system heat pump, a "no heat/no cooling" service call, you turn the thermostat to the fan on/cont position and the indoor fan operates. This action verifies that;
the compressor is operable
the system has proper air flow
there is high voltage supply to the outdoor unit
the transformer is functioning
on most air-to-air heat pumps;
The indoor and outdoor coils are same physical size and capacity
The indoor and outdoor coils are different physical size and capacity
airflow must be reduced over the indoor coil during the cooling mode
airflow must be reduced over the indoor coil during the heating
a heat pump system, operating at 45° F ambient, may be ______ efficient than electric resistance heat
just as
3 to 4 times more
8 to 10 times more
2 to 3 times less
Since electric resistance heat provides 1 watt of usable heat for each watt of energy purchased, electric resistance heat has a COP of;
1:1
2:1
3:1
1:2
As outside ambient air temperature decreases, a heat pump's COP will;
increases
decreases
remains the same
fluctuates up and down
During the defrost cycle, the system switches to the _______ mode
heating
pump down
emergency heating
cooling
During the heating mode, the refrigerant in the indoor coil is under;
low pressure
high pressure
atmospheric pressure
vacuum
What three things happen on most air-to-air heat pump during defrost?
the outdoor fan must run, the indoor fan must stop, and the time guard circuit must be energized
the compressor shuts off, superheat air comes out of the registers, and a strange smell fills the conditioned space
the reversing valve must switch to cooling mode, the outdoor fan shuts off and auxiliary heat is energized
the reversing valve must switch to heating mode, the outdoor fan shuts off and auxiliary heat is energized
High suction pressure and low discharge pressure on a heat pump system operating in either the heating or cooling mode can be an indication of;
overheated compressor moto whining
a stuck closed check valve
compressor inefficiency
a restricted metering device
the preferred method to perform adjustments to the refrigerant charge in the heat pump system is in the _______ mode.
heat
cooling
defrost
emergency heat
You answer a service call for insufficient heat. You find the suction pressure is higher and discharge pressure is lower than normal. Using a digital thermometer, you measure the line entering the reversing valve from the compressor discharge and find 215° F You then measure the line leaving the reversing valve that connects to the indoor coil and find 185° F. These readings are an indication of;
a damaged compressor
a faulty reversing valve
a stuck defrost relay
a low refrigerant charge
The customer complaint is not enough heat. You install service gauges and find the low side pressure is higher than normal and the high side pressure is lower than normal. You switch the system to the cooling mode and find the pressures are normal. The most likely cause of the problem is;
a stuck open check valve at the outdoor coil
a stuck open check valve at the indoor coil
defective compressor valves
a stuck closed check valve at the outdoor coil
A customer complains that their heat pump system blows cool air periodically during the heat mode. This could be caused by;
A faulty defrost relay (does not energize the aux. heat during the defrost mode)
an undersized indoor coil
a oversized outdoor coil
thermostat set to emergency heat
When a heat pump is in the heating mode, what can cause frost accumulation on the outdoor coil when the ambient temperature is 45F?
The outdoor coil is colder than the ambient air
45°F air contains a high percentage moisture that will freeze
more cold air is being removed from the conditioned space
the filter drier is clogged
The indoor fan on a heat pump system operates;
through a temperature controlled fan switch
at the same speed for heating or cooling
in the same manner as a gas or oil heating system
at a low speed for heating and high speed for cooling
the defrost cycle can be initiated by;
pressure drop across the indoor coil
pressure rise across the outdoor coil
time and temperature
the outdoor thermostat
the defrost cycle can be terminated by;
pressure drop across the indoor coil
pressure rise across the outdoor coil
time/temperature
the outdoor thermostat
Movement of the piston in the reversing valve is accomplished by;
add compressor discharge pressure to both sides of the piston
remove compressor discharge pressure from both sides of the piston
bleeding pressure from one side of the piston to the suction side of the compressor
solenoid coil
Some close coupled (package unit) heat pumps use an electronic expansion valve to meter refrigerant. One advantage to using an electronic expansion valve is;
electronic expansion valves operate at reduced head pressure
electronic expansion valves can meter refrigerant in either direction
electronic expansion valves do not require a filter-drier
no auxiliary heat needed to supplement heat pump
Liquid line filter/driers that are used on a heat pump system;
are designed with four connector for connection to 4 way valve
must be installed in conjunction with bi-flow check valves
must be installed in series with check valves
must be a bi-flow design if used without a check valve
When installing the heat pump outdoor units, care should be taken to provide for drainage during _______ cycle.
heating
cooling
defrost
emergency heat
The indoor coil is usually mounted in the airstream _______ the auxiliary heat strips.
before
after
parallel to
downstream of
On Dual fuel system, the indoor coil must be located;
before the heat exchanger
after the heat exchanger
in the heat exchanger
parallel to the heat exchanger
Air-to-air heat pumps are most practical to operate in areas where the lowest winter temperature does not go below ______ °F
+10
-10
-20
-30
Air-to-air heat pumps, operating without auxiliary heat, provides air to the registers that is approximately _____ °F or less
100
140
160
200
The most common method of defrosting the outdoor coil on an air source heat pump is;
auxiliary electric heaters
supply air
exhaust vent air
reverse cycle defrost
COP is the abbreviation for;
coefficient of performance
common operating procedure
cost of performance
coefficient of power
At temperatures above 45 degrees F, the heat pump refrigeration cycle permits the;
condenser to release 3 to 4 times more heat than it takes in electrical energy to drive the compressor
evaporator to release 3 to 4 times more heat than it takes in electrical energy to drive the compressor
compressor to pump 3 to 4 times more refrigerant in the heating mode than in the cooling mode
compressor to absorb 3 to 4 times more heat than it takes in electrical energy to drive the compressor
in addition to heat from the outdoor coil, a heat pump in the heating mode will get heat from;
solar
adhesion
reactance
compression
When operating in the heat mode, hot gas leaves the compressor and first flows to;
the outdoor coil
the indoor coil
the accumulator
the reversing valve
When operating in the cooling mode, hot gas leaves the compressor and first flows to;
the outdoor coil
the indoor coil
the accumulator
the reversing valve
to make the reversing valve slide move, the system must have a pressure difference of;
10 to 20 psig
25 to 40 psig
75 to 100 psig
160 to 200 psig
Before connecting a manifold gauge set to a heat pump system, you should first;
make sure that the customer understands that there may be a de-minimums loss of refrigerant
check the superheat
check the head pressure
verify the operating mode of the system
in the heat mode, the suction line entering the compressor contains;
high pressure / low temperature liquid
low pressure / high temperature liquid
low pressure / low temperature vapor
high pressure / high temperature vapor
the reversing valve is often referred to as a ;
three-way valve
two - way valve
four-way valve
nonincriminating valve
A heat pump has a thermostatic expansion valve (TEV) and a check valve at each coil. When the modes are reversed;
the check valves insure the system will work even if the reversing valve fails
the TEVs will direct the refrigerant to the check valves
refrigerant will bypass the TEV on the coil serving as the condenser
refrigerant will bypass the TEV on the coil serving as the evaporator
Mechanically troubleshooting a reversing valve can be done by;
the checking the pressure difference between low and high side of the system
by checking the temperature differential between the connection serving the low side
checking for correct voltage to the pilot solenoid
touching the valve body at the connection serving the high side with the system off
compressors designed for heat pumps differs from compressors designed for A/C in that;
it is built with smaller bearing surfaces
it must move a higher volume at lower pressures of refrigerant
it must accommodate refrigerants at higher specific gravities
it is designed to operate at high compression ratios
One of the most important devices to insure the longevity of a heat pump's reciprocating compressor is the;
high or low pressure switch
pressure relief valve
crankcase heater
reversing valve
A heat pump can be difficult to charge properly because;
heat pumps can only be charged in the cooling mode
heat pumps can only be charged in the heating mode
heat pumps require that the system is off and the refrigerant is weighted in
of low ambient conditions
High efficient heat pump systems, charged with R-104A refrigerant normally use a;
fixed orifice metering device for the heating and cooling cycle
fixed orifice metering device for the heating cycle and TXV for the cooling cycle
TXV metering device for the heating and a fixed orifice metering device cooling cycle
AXV metering device for the heating and a fixed orifice metering device cooling cycle
When heat pump is operating in the cooling mode, the;
refrigerant is by-passing the indoor metering device and the indoor check valve is opened
refrigerant is by-passing the indoor metering device and the indoor check valve is closed
indoor metering device is metering refrigerant and the outdoor check valve is open
outdoor metering device is metering refrigerant and the outdoor check valve is closed
When in the cooling mode, the low pressure refrigerant vapor leaves the reversing valve and travels to the;
indoor coil and then to the outdoor coil
accumulator and then to the compressor.
compressor and then to the accumulator
accumulator and then the indoor coil
