HVAC NATE Heat Pump – Questions & Solutions
On an R-22 system, line diameters and lengths are typically specified for a
vapor pressure drop that does not exceed what? ✔️Ans - 6-7PSI or 6F
What is the primary purpose of using flux when soldering copper or brass
parts? ✔️Ans - Prevent Oxidation
The water that results from a defrost cycle of an air to air heat pump(runoff)
must? ✔️Ans - Drain off and away from the outdoor coil.
Why must the runoff be drained off and away from the outdoor coil? ✔️Ans -
Excessive ice can build up on the bottom of the coil and can reduce capacity.
What is the component that reduces sound transmission and prevents water
leaks of a package heat pump installed on a roof? ✔️Ans - Curb Gasket
Why do you need to add a control for a heat pump indoor coil that is installed
on a fossil fuel furnace? ✔️Ans - So the heat pump and furnace do not
operate at the same time in normal heating.
What happens when you energize a hermetic refrigeration compressor and
the system is in a deep vacuum? ✔️Ans - Motor windings could become
damaged.
What needs to happen in order to consider an evacuation to be complete?
✔️Ans - System should be evacuated to a vacuum of 500 Microns or below.
A system is supplied from the factory with charge for a 15 foot line set. The
data plate shows the required system charge to be 5 pounds 10 ounces. The
line set uses a 3/8 inch liquid line and is 25 feet long. The manufacturer's
instruction sheet specifies 0.6 ounces of refrigerant to be added for each
added foot of refrigerant line length. How much refrigerant is needed to
completely charge the system? ✔️Ans - 6lbs
Where are drive slips typically installed? ✔️Ans - On the shorter sides of
rectangular duct.
,What is a necessary check to properly set a heat anticipator? ✔️Ans -
Heating control circuit amperage
draw.
A heat pump operating in normal ice free conditions maintains a certain
temperature difference between the outdoor coil temperature and the
surrounding outdoor ambient. What is this temperature referred to as?
✔️Ans - Coil TD.
What is the smallest refrigerant leak that an electronic leak detector should be
capable of sensing? ✔️Ans - .o5oz per year.
When checking the pressures in an operating system with a manifold gauge
set, will refrigerant oil in a hose will have an effect on the gauge? ✔️Ans - No
What is the absolute pressure at sea level if a gauge pressure is 35 psig?
✔️Ans - 49.7psia
100,000 BTUH output furnace.
Return air temp is 65F.
Supply air is 135F.
What is the CFM? ✔️Ans - 1323CFM
What is the best method of repair when a residential supply diffuser is noisy
because of a loose vane? ✔️Ans - Replace the diffuser.
When performing preventive maintenance on a heat pump what should the
technician check and why? ✔️Ans - Outdoor fan. To be certain it runs freely
with no binding.
What is the effect of 170 volts supplied to a 208/230 volt compressor? ✔️Ans
- Would cause the current to increase and the motor may trip on overload.
On a service call for a cooling problem with a heat pump, your inspections find
a liquid line that has condensation on it. What is most likely to cause this?
✔️Ans - Restriction in the liquid line.
What is a reason for cool air complaints when a heat pump is operating in the
heating cycle? ✔️Ans - Excessive supply air velocities.
, The following measurements are recorded on an operating heat pump system.
The heat pump is operating with the compressor only with no auxiliary heat:
• Heat pump only supply air temperature 92°F
• Heat pump only return air temperature 70°F
• Outdoor temperature 54°F
• Supply air temp. /auxiliary heat ON 115°F
• Return air temp. /auxiliary heat ON 70°F
• CFM 1228
What is the heating capacity in BTUH? ✔️Ans - 29,177 BTU/H
Inadequate heating can be caused by what? ✔️Ans - Dirty or clogged air
filter.
To minimize noise problems in residential duct systems, what is the range
(recommended to maximum) of design air velocity in the rectangular main
supply trunk? ✔️Ans - 700 to 900 fpm
conditions while checking a packaged heat pump in cooling.
• The unit has a piston type metering device on both the indoor and outdoor
coils.
• Outdoor temperature 75°F
• Superheat 55°F
What is wrong with the system? ✔️Ans - Undercharged.
What will you get when a capillary tube is overcharged? ✔️Ans - low
superheat and high sub cooling
On an R-22 system, line diameters and lengths are typically specified for a
vapor pressure drop that does not exceed what? ✔️Ans - 6-7PSI or 6F
What is the primary purpose of using flux when soldering copper or brass
parts? ✔️Ans - Prevent Oxidation
The water that results from a defrost cycle of an air to air heat pump(runoff)
must? ✔️Ans - Drain off and away from the outdoor coil.
Why must the runoff be drained off and away from the outdoor coil? ✔️Ans -
Excessive ice can build up on the bottom of the coil and can reduce capacity.
What is the component that reduces sound transmission and prevents water
leaks of a package heat pump installed on a roof? ✔️Ans - Curb Gasket
Why do you need to add a control for a heat pump indoor coil that is installed
on a fossil fuel furnace? ✔️Ans - So the heat pump and furnace do not
operate at the same time in normal heating.
What happens when you energize a hermetic refrigeration compressor and
the system is in a deep vacuum? ✔️Ans - Motor windings could become
damaged.
What needs to happen in order to consider an evacuation to be complete?
✔️Ans - System should be evacuated to a vacuum of 500 Microns or below.
A system is supplied from the factory with charge for a 15 foot line set. The
data plate shows the required system charge to be 5 pounds 10 ounces. The
line set uses a 3/8 inch liquid line and is 25 feet long. The manufacturer's
instruction sheet specifies 0.6 ounces of refrigerant to be added for each
added foot of refrigerant line length. How much refrigerant is needed to
completely charge the system? ✔️Ans - 6lbs
Where are drive slips typically installed? ✔️Ans - On the shorter sides of
rectangular duct.
,What is a necessary check to properly set a heat anticipator? ✔️Ans -
Heating control circuit amperage
draw.
A heat pump operating in normal ice free conditions maintains a certain
temperature difference between the outdoor coil temperature and the
surrounding outdoor ambient. What is this temperature referred to as?
✔️Ans - Coil TD.
What is the smallest refrigerant leak that an electronic leak detector should be
capable of sensing? ✔️Ans - .o5oz per year.
When checking the pressures in an operating system with a manifold gauge
set, will refrigerant oil in a hose will have an effect on the gauge? ✔️Ans - No
What is the absolute pressure at sea level if a gauge pressure is 35 psig?
✔️Ans - 49.7psia
100,000 BTUH output furnace.
Return air temp is 65F.
Supply air is 135F.
What is the CFM? ✔️Ans - 1323CFM
What is the best method of repair when a residential supply diffuser is noisy
because of a loose vane? ✔️Ans - Replace the diffuser.
When performing preventive maintenance on a heat pump what should the
technician check and why? ✔️Ans - Outdoor fan. To be certain it runs freely
with no binding.
What is the effect of 170 volts supplied to a 208/230 volt compressor? ✔️Ans
- Would cause the current to increase and the motor may trip on overload.
On a service call for a cooling problem with a heat pump, your inspections find
a liquid line that has condensation on it. What is most likely to cause this?
✔️Ans - Restriction in the liquid line.
What is a reason for cool air complaints when a heat pump is operating in the
heating cycle? ✔️Ans - Excessive supply air velocities.
, The following measurements are recorded on an operating heat pump system.
The heat pump is operating with the compressor only with no auxiliary heat:
• Heat pump only supply air temperature 92°F
• Heat pump only return air temperature 70°F
• Outdoor temperature 54°F
• Supply air temp. /auxiliary heat ON 115°F
• Return air temp. /auxiliary heat ON 70°F
• CFM 1228
What is the heating capacity in BTUH? ✔️Ans - 29,177 BTU/H
Inadequate heating can be caused by what? ✔️Ans - Dirty or clogged air
filter.
To minimize noise problems in residential duct systems, what is the range
(recommended to maximum) of design air velocity in the rectangular main
supply trunk? ✔️Ans - 700 to 900 fpm
conditions while checking a packaged heat pump in cooling.
• The unit has a piston type metering device on both the indoor and outdoor
coils.
• Outdoor temperature 75°F
• Superheat 55°F
What is wrong with the system? ✔️Ans - Undercharged.
What will you get when a capillary tube is overcharged? ✔️Ans - low
superheat and high sub cooling
