HW 69
Why is a heat pump called a heat pump?
It moves heat from a low temperature heat source to a higher temperature heat sink
What type of heat pump is the most common and why?
Air to air heat pumps are the most common heat pumps in use today because they are generally less expensive and easier to install than other types of heat pumps.
What is the main difference between a heat pump and a fossil fuel furnace?
Heat pumps move heat instead of creating it.
What does the O thermostat terminal energize on most heat pumps?
The reversing valve
Why are bi-flow filter driers used on heat pumps instead of standard filter driers?
The refrigerant in the liquid line reverses directions between the heating and cooling cycle. Debris caught by a regular drier would be flushed out when the cycle reversed.
Where in the airstream are electric strip heaters installed?
The electric strip heaters are normally installed after the blower.
The indoor coil is the condenser in in the heating or the cooling cycle?
The heating cycle.
What is the most common form of auxiliary heat used in heat pumps?
Electric resistance strip heat
How is the refrigeration cycle reversed in a heat pump?
A reversing valve which reverses the direction of refrigerant flow
What are some advantages of the mini-split heat pump?
Mini-split units have no duct losses. The indoor section is sleek and attractive and will not block incoming light such as a standard window mounted air conditioner. Each space has its own thermostat, which allows for reducing the cooling or heating supply when no one is there, which will save on energy costs
The outdoor coil is the condenser in the cooling cycle or the heating cycle?
The cooling cycle.
As the outside air temperature drops, the heating efficiency of air-to-air heat pumps does what?
Decreases.
What is the difference between an EER and a SEER?
EER is a steady state measurement that does not take into consideration starting, stopping, and different operating conditions. SEER is a seasonal measurement that takes all these factors into account.
What is a dual fuel heat pump?
A heat pump system that uses a gas or oil furnace as the auxiliary heat is known as a dual fuel, or hybrid heat pump system.
Why are both lines of a mini-split system insulated?
Because there is only one metering device
Which terminal controls second-stage heat on most heat pumps?
W terminal
Why are accumulators and/or charge compensator tanks necessary in air source heat pumps?
Air source heat pumps circulate less refrigerant at low ambient temperatures and the refrigerant not being used must be stored somewhere
Describe what happens during the defrost cycle?
The defrost cycle is similar to the cooling cycle, except that the outdoor fan is de-energized and the strip heaters are energized.
How can an air-source heat pump heat when the outdoor temperature is cold?
All molecules contain some heat until they reach absolute zero (-460°F)
The heat exchanger, also called a coil, in an air-to-air heat pump, which is expelling heat from the refrigerant:
Is performing the work of a condenser.