Evaporators, Compressors & Condensers
More than one evaporator coil circuit is used when?
There would be excessive refrigerant pressure drop in the coil circuit
What refrigerant lines must be field-installed on a package unit?
No lines need to be field-installed.
Average core body temperature?
98.6 F
If structure has no attic?
Roof must have sufficient insulation.
Wet-bulb depression is?
Difference between dry- and wet-bulb temps.
In reciprocating compressors, the motor is mainly cooled by?
Both air over the shell and suction gas return.
Popular evaporator material combo?
Copper tube–aluminum fin.
Most occupants set temperature to?
75F
Supply ducts need insulation when?
When run through unconditioned spaces.
Wet-bulb thermometer measures?
Moisture content of air.
In rotary compressors, the motor is cooled by?
Suction gas returning to the compressor.
What are three common evaporator designs?
A-coil, H-coil, slant coil.
Comfort described as?
Balance of temperature, humidity, air movement, and cleanliness.
Return ducts never need insulation?
False
Humidity if wet/dry bulb are 80°F?
100%
Most of the heat in suction vapor entering the compressor is?
Superheated from the evaporator.
Three types of expansion devices are?
TXV, capillary tube, and orifice.
Air contains approx. 78% what?
Nitrogen
After screw holes strip in condenser?
Do NOT reuse same size screws.
Dew-point temperature is?
Temp where moisture begins to condense.
High-efficiency condensers have what advantage?
They have more surface area than standard condensers.
The condenser in a system does what?
Desuperheats, condenses, and subcools refrigerant.
When is the human body comfortable?
When heat produced = heat lost to surroundings.
Best window placement in desert?
North and east sides of house.
What does sling psychrometer do?
Measures wet and dry bulb temps with spinning.