HVAC 101
It takes ___ Btu to melt one pound of ice at 32°F
144btu
What is the wet bulb if you have a 85 degree dry bulb at 34% relative humidity?
65 degree wetbulb
What state is the refrigerant when it leaves the evap?
Low pressure/low temp vapor
What is the difference in Rc and Rh?
Hot for cooling and hot for heating
Which color of the Thermostat energizes the outside contactor?
Yellow
The ____ relationship correlates the vapor pressure and the boiling point of water and is the basis for controlling the cooling system’s temperatures.
pressure and temperature
How many known metrics do you need in order to determine an unknown metric?
When the refrigerant leaves the compressor what state is it?
High pressure/temp vapor
What is W2 on a tstat
2nd stage heating
What causes a TXV to open more?
If the refrigerant leaving the evaporator is too warm and the pressure is low, the valve will open to allow more refrigerant in.
How many BTUs in a 5 ton ac system?
60,000 btus
Of the heat produced in the human body, which is by perspiration?
a.Conduction.
b.Convection.
c.Radiation.
d.Evaporation.
d.Evaporation.
What is the filter dyers job?
The catch non condensable like moisture.
Which terminal on the tstat controls the heat?
W terminal
What causes the TXV to close,
If the refrigerant leaving the evaporator is too cool and the pressure is high, the valve will close to allow less refrigerant in.
What is a manometer used for?
pressures lower that PSIG,
gas, static pressure.
Infiltration is the term used when referring to the air entering a structure ____.
a.through an air make-up unit
b.around doors and windows
c.through ventilation
d.because of street traffic
b.around doors and windows
Explain Super heat
The temp increase from inside the evap coil to when it leaves the evap.
what is the different in the o and b terminals of a thermostat?
The O terminal is energized during cooling cycles, while the B terminal is energized during heating cycles.
What pushes the plugger in a reversing valve causing the slider to move?
high pressure refrigerant from the compressor discharge line.
What is an anemometer used for?
To measure air flow.
An attic that is 95 degrees with a 100 grains of moisture will have a dew point of?
67 degrees
What is sub cooling
The decrease in temp from inside the condenser coil to when it leaves the condenser.
What does a blown fuse on a control board indicate?
A low voltage short
what is the temperature inside the coil referred to?
saturation temperature