Heat Pump Prep Test
COP is the abbreviation for;
Coefficient of performance
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
When a heat pump is operating in the heat mode, the suction line at the compressor will feel;
Cold and sweaty
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;
Compressor inefficiency
One of the most important devices to insure the longevity of a heat pump's reciprocating compressor is the;
Crankcase heater
When installing the heat pump outdoor units, care should be taken to provide for drainage during _______ cycle.
Defrost
What is the difference between "demand defrost" and "timed defrost?"
Demand defrost happens only when needed and timed defrost is based on time/temperature
SEER is calculated by
Dividing the BTUs removed by the watts consumed during the cooling season
which of the following are innovations that may be found on new high efficiency units?
ECM fan motors
At temperatures above 45 degrees F, the heat pump refrigeration cycle permits the;
Evaporator to release 3 to 4 times more heat than it takes in electrical energy to drive the compressor
On a time initiation/temperature termination defrost, the defrost time clock hase one N.O. and one N.C.: switch. When do the positions of these switches change?
Every 30 to 90 minutes, depending on the cam installed in the timer
on a water source heat pump, the heat mode water regulating valve must be
Reverse acting
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
Reversing Valve
Which component is responsible for changing the direction of the flow of refrigerant?
Reversing valve
High efficient heat pump systems, charged with R-104A refrigerant normally use a;
TXV metering device for the heating and a fixed orifice metering device cooling cycle
in order to determine a heat pump's balance point, you must first calculate
The building's heat load
What would be the result of closing registers in room that are uninhabited while operating in the heating mode?
The discharge pressure and temperature will rise decreasing the life span of the unit
What is the difference on most air-to-air heat pumps;
The indoor and outdoor coils are different physical size and capacity
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
What three things happen on most air-to-air heat pump during defrost?
The reversing valve must switch to cooling mode, the outdoor fan shuts off and auxiliary heat is energized
which type of heat pump does not require a defrost cycle?
Water source
Heat pump systems which use a thermostatic expansion valve at each coil will also have;
a by-pass lines with check valve
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 215F. You then measure the line leaving the reversing valve that connects to the indoor coil and find 185F. These readings are an indication of;
a faulty reversing valve
what is the industry standard for maximum duration for defrost?
a maximum of 10 minutes
off-cycle crankcase heat is provided by
a small amount of current is passed through the start capacitor to heat the start winding
A heat pump operates satisfactorily in the cooling mode, but not in the heat mode. This could be caused by;
a stuck check valve or clogged txv screen
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
When in cooling mode, the low pressure refrigerant vapor leaves the reversing valve and travels to the;
accumulator and then the compressor
When in the cooling mode, the low pressure refrigerant vapor leaves the reversing valve and travels to the;
accumulator and then to the compressor.
On Dual fuel system, the indoor coil must be located;
after the heat exchanger
You are checking for proper airflow in CFM on a three ton heat pump system. The system has one return grill measuring 24" x 24", whcih 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
a high efficiency heat pump system designed to function from high to low ambient conditions below 10F, may have? \
an auxiliary heat exchanger injected with an ethylene glycol solution
the temperature difference between the 1st and 2nd bulbs for heating on a heat pump thermostats is
approximately 2 F
The indoor fan on a heat pump system operates;
at the same speed for heating or cooling
The indoor coil is usually mounted in the airstream _______ the auxiliary heat strips.
before
Movement of the piston in the reversing valve is accomplished by;
bleeding pressure from one side of the piston to the suction side of the compressor
Mechanically troubleshooting a reversing valve can be done by;
by checking the temperature differential between the connection serving the low side
the most preferred method of charging any system in the field is
by weight
in addition to heat from the outdoor coil, a heat pump in the heating mode will get heat from;
compression
During the defrost cycle, the system switches to the _______ mode
cooling
the preferred method to perform adjustments to the refrigerant charge in the heat pump system is in the _______ mode.
cooling
when a heat pump is used for heating and cooling, the system is sized by the
cooling load
As outside ambient air temperature decreases, a heat pump's Cop will;
decreases
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 can meter refrigerant in either direction
when the heat pump compressor has malfunctioned, the customer has the option to switch the system into
emergency heat mode
Some heat pump system use a ___________as a metering device
fixed orifice
the reversing valve is often referred to as a ;
four-way valve
A heat pump can be difficult to charge properly because;
heat pumps can only be charged in the cooling mode
During the heating mode, the refrigerant in the indoor coil is under;
high pressure
the air-to-air heat pump outdoor unit is most efficient if located
in a moderate climate zone
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 380F. You switch to cooling mode and determine a temperature split of 29F. The most likely corrective action (relative to airflow) is;
increase the indoor fan
When a heat pump is operating in the cooling mode, the;
indoor metering device is metering refrigerant and the outdoor check valve is open
When heat pump is operating in the cooling mode, the ;
indoor metering device is metering refrigerant and the outdoor check valve is open
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
Refrigerant flow though the compressor;
is always the same regardless of operating mode
A scroll type compressor;
is less susceptible to damage from liquid flood-back
compressors designed for heat pumps differs from compressors designed for A/C in that;
it is designed to operate at high compression ratios
in the heat mode, the suction line entering the compressor contains;
low pressure/low temperature vapor
what is the industry standard for deep vacuum?
maintain 500 microns for 15 minutes
Liquid line filter/driers that are used on a heat pump system;
must be a bi-flow design if used without a check valve
The thermostat that controls the auxiliary electric heat according to the outdoor temperature is called
outdoor ambient thermostat
A heat pump has a thermostatic expansion valve (TEV) and a check valve at each coil. When the modes are reversed;
refrigerant will bypass the TEV on the coil serving as the condenser
The most common method of defrosting the outdoor coil on an air source heat pump is;
reverse cycle defrost
How may a lockout (impedance) relay be reset?
simply disconnect power to the unit momentarily
the heat pump defrost board can be manipulated by the technician to
simulate the defrost cycle
At what temperature is an outdoor ambient thermostat normally set
slightly above the initial balance point
The slide valve and piston in the reversing valve is actuated by pressure directed through the;
solenoid and pilot valve
Because of the possibility of liquid flood-back, a heat pump that uses a reciprocating compressor should be equipped with a;
suction accumulator
The use of a scroll type compressor on a heat pump can eliminate the need for a ;
suction line accumulator
Start-up with a night set back digital thermostat requires the technician to always
teach the customer how to program the thermostats
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;
the charge is critical, sometimes plus/minus 1/2 oz. refrigerant
During the cooling cycle, the indoor coil becomes;
the evaporator
During the heating cycle, the outdoor coil is used as;
the evaporator
When operating in the heat mode, hot gas leaves the compressor and first flows to;
the indoor coil
When operating in the cooling mode, hot gas leaves the compressor and first flows to;
the outdoor coil
the outdoor coil is frozen solid on a "no heat" service call. The most likely reason is
the outdoor fan is inoperative
what control operates the 1st stage of secondary heat?
the second heating stage of the indoor thermostat
what will happen 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
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 transformer is functioning
the defrost cycle can be initiated by;
time and temperature
the defrost cycle can be terminated by;
time/temperature
During the defrost cycle, the outdoor fan is usually;
turned off
Good service practice for installation of a reversing valve includes
use heat paste and wet rags while brazing in the new valve
if manufacturers specifications are not available, a good way to calculate cubic feet per minute through a coil is
use temperature rise on emergency heat mode
Before connecting a manifold gauge set to a heat pump system, you should first;
verify the operating mode of the system
Air-to-air heat pumps are most practical to operate in areas where the lowest winter temperature does not go below ______ F
+10
Air-to-air heat pumps, operating without auxiliary heat, provides air to the registers that is approximately _____F or less
100
An R-410A heat pump operating in the cooling mode has a suction pressure of 120 pisg. Adding 2 psig for pressure drop in the coil, the true outlet pressure is 131 psig. The temperature of the suction line at the outlet of the evaporator is 57 F. What is the superheat?
12 degrees
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
a heat pump system, operating at 45F ambient, may be ______ efficient than electric resistance heat
3 to 4 times more
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
what is the recommended CFM across the evaporator coil of a heat pump?
400 to 450 CFM
to make the reversing valve slide move, the system must have a pressure difference of;
75 to 100 psig
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)
Room thermostats for heat pump should be installed
As near to the main return air grill as possible
Heat pump heating mode efficiency is rated in
AFUE
