HVAC NATE Heat Pump/ 171 Q&A/ Already Graded A+ Terms like:
What is the absolute pressure at sea level if a gauge pressure is 35 psig? - Answer: 49.7psia
100,000 BTUH output furnace.
Return air temp is 65F.
Supply air is 135F.
What is the CFM? - Answer: 1323CFM
What is the best method ...
HVAC NATE Heat Pump/ 171 Q&A/ Already
Graded A+
What is the absolute pressure at sea level if a gauge pressure is 35 psig? - Answer: 49.7psia
100,000 BTUH output furnace.
Return air temp is 65F.
Supply air is 135F.
What is the CFM? - Answer: 1323CFM
What is the best method of repair when a residential supply diffuser is noisy because of a loose
vane? - Answer: Replace the diffuser.
When performing preventive maintenance on a heat pump what should the technician check
and why? - Answer: 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? - Answer: Would cause
the current to increase and the motor may trip on overload.
Page 1 of 21
,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? - Answer: Restriction in the liquid line.
What is a reason for cool air complaints when a heat pump is operating in the heating cycle? -
Answer: 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? - Answer: 29,177 BTU/H
Inadequate heating can be caused by what? - Answer: 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? - Answer: 700 to 900 fpm
conditions while checking a packaged heat pump in cooling.
Page 2 of 21
, • 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? - Answer: Undercharged.
What will you get when a capillary tube is overcharged? - Answer: low superheat and high sub
cooling
What is the effect of a low charge on the switchover operations of a reversing valve? - Answer:
Reversing valves are less likely to transfer if charge is low.
A technician is working on a heat pump with a capacitor start-capacitor run compressor. On
initial startup, the compressor hums momentarily and the shuts down on internal overload.
What is the problem? - Answer: Too great a pressure difference on the compressor.
A step down transformer has a rating of 40 VA. Its primary voltage is 120V with a secondary
voltage of 24V. What is the maximum current draw of a load connected to this transformer? -
Answer: 1.7amps
What does a bright red or orange glow from the resistance element in a duct heater indicate? -
Answer: Flow of air is insufficient.
What does the outdoor fan do during defrost on a heat pump and why? - Answer: The fan stops
to minimize defrost time.
Page 3 of 21
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