Week 5 Unit 73 HW Review Questions

List the four main categories into which heat pump problems can be grouped.

• Electrical problems, Airflow problems, Refrigeration problems, and Defrost problems.

• Same as AC, just no defrost.

What are some symptoms of restricted airflow in a heat pump system?

• Cooling:

  Larger than normal air temperature drop across the indoor coil.

  Low pressures

  Low superheat

  Heating:

              Higher than normal temperature rise across the indoor coil.

              High Pressures

              High subcooling.

• all that

How does outdoor temperature affect the indoor air temperature rise of a heat pump?

• As the outdoor temperature drops, the air temperature rise across the indoor coil decreases.

• The other one

How often should throwaway filters be checked?

• Every 30 days. 

• yep

Why should automotive oil never be used to lubricate blower motors?

• They are for cars

• There are detergents in the oil which prevent the oil from lubricating the sintered sleeve bearings

Where should motors be oiled?

• Only lubricate blower motors at the oiler holes.

• The windings

What is the preferred position for a reversing valve main valve body and pilot valve?

• to the side

• The preferred position is with the main piston is in a horizontal position and the pilot valve is higher than the main valve.

How can you protect the reversing valve body from overheating when installing a new reversing valve?

• By wrapping the body with some type of heat-absorbing material or with a water-saturated cloth.

• blowing cold air on it

What is the maximum temperature the reversing valve body will tolerate?

• 85°F

• 250°F

List the methods of checking refrigerant charge in the heating cycle.

• System pressure charts that correspond to indoor and outdoor temperatures

  Indoor air temperature rise that corresponds to outdoor temperature

  Discharge line superheat (usually 50°F to 60°F)

  Discharge line approach (usually 100°F to 110°F above ambient)

• none are very accurate