CATEGORY 1: SOLAR LOAD & HEAT GAIN
Q: What direction should most windows face in a desert climate to reduce solar load?
A: North and South.
What is the most common coil construction in HVAC systems?
Copper tube with aluminum fin.
What cools the motor in most reciprocating compressors?
Air over the shell and suction gas.
What happens to system efficiency when the condenser coil is dirty?
Efficiency decreases.
Which system type is factory assembled and pre-charged with refrigerant?
Package unit.
What is the main source of solar load on a structure?
Radiation from the sun.
Why do some evaporator coils use multiple circuits?
To avoid excessive refrigerant pressure drop.
What cools the motor in most rotary compressors?
Discharge gas.
Why do high-efficiency condensers have more surface area?
To improve heat rejection.
How many refrigerant lines must be field-installed on a package unit?
None.
Why must moisture levels be considered when selecting air-conditioning equipment?
Humidity adds latent load that the evaporator must remove.
At normal conditions, what is a standard evaporator boiling temperature?
Around 40°F.
Why is suction gas useful for cooling a compressor motor?
Because it absorbs heat before being compressed.
Why should stainless steel screws be used in salt-air environments?
To prevent corrosion.
What is the biggest appearance drawback of ductless split systems?
They are visible on the interior wall.
What happens to heat gain in a home with no attic if the roof is not insulated?
The occupied space overheats due to increased heat gain.
What is a typical evaporator superheat under normal operating conditions?
About 10°F.
What happens to compressor temperature when airflow over the condenser is blocked or restricted?
Temperature rises, causing overheating and high head pressure.
Why can high-efficiency condensers be “too efficient” on cool days?
Head pressure can drop too low, reducing refrigerant flow.
Package units are generally more efficient than split systems because they are ________.
Factory assembled, sealed, and charged.
Why must humidity be treated as part of the total cooling load?
Because the evaporator absorbs both sensible and latent heat.
High-efficiency systems boil refrigerant at a slightly higher temperature. What is that temperature?
About 45°F.
Which compressor type is more sensitive to liquid floodback and why?
Rotary compressors — because liquid refrigerant washes oil out of the compression chamber.
How does condenser location affect performance?
Shaded, open-air locations improve heat rejection, while tight/hot areas reduce performance.
Which system type is best for buildings without indoor mechanical rooms?
Rooftop package units.