MD HVAC MASTERS EVALUATION LATEST
UPDATED QUESTIONS AND ANSWERS SURE A+
✔✔Evaporator - ✔✔Absorbs heat into the system, and turns the liquid refrigerant from
the metering device to a vapor. Must be a temperature that is cooler than the air to be
cooled, usually 10-20 degrees cooler in refrigeration and 35 degrees F cooler in air
conditioning,
✔✔Compressor - ✔✔Pumps heat through the system, and reduces the pressure on the
low pressure side of the system and increases the pressure on the high pressure side
✔✔Condenser - ✔✔Rejects heat, and take the high pressure gas from the compressor
and turns the refrigerant into a liquid which gives off heat to the outside air, should be
30 degrees warmer than the outside air
✔✔Metering Device (Expansion Device) - ✔✔Holds back the flow of refrigerant only
pure liquid must enter it but is restricted, it creates flash gas
✔✔Reciprocating Compressor - ✔✔Uses a piston in a cylinder to compress the
refrigerant and valves make sure the refrigerant is flowing in the right direction
, ✔✔Rotary Compressor - ✔✔Uses a rotating drum-like piston that squeezes the
refrigerant vapor out of the discharge line, Typically used for applications on smaller
equipment like window air conditioners.
✔✔Scroll Compressor - ✔✔The movable parts orbit inside the stationary scroll and
squeezes the vapor from the low pressure side to the high pressure side between the
movable stationary parts, and is then discharge in the center of the spiral stationary
scroll
✔✔Compressor Ratio - ✔✔Add fifteen to each side and divide high pressure from low
pressure usually 10:1 refrigeration and 3:1 in air conditiong
✔✔Charles Law - ✔✔By reducing the volume in a cylinder you increase the temperature
of the gas
✔✔Saturated Vapor - ✔✔Occurs when the liquid is all boiled away to a vapor and it is
saturated with heat, but if heat is taken away it will turn back to a liquid
✔✔Flooded Evaporator - ✔✔When a evaporator is operated full of liquid refrigerant and
are equipped with a device that prevents the liquid from entering the compressor.
✔✔Starved Coil - ✔✔When the metering device isn't feeding enough refrigerant to the
coil
✔✔BTU (British Thermal Unit) - ✔✔Is the amount of heat required to raise the
temperature of 1 lb of water 1 degree F. 1 watt = 3.412 btu's, 3,412 btu= 1 KW. There
are 12,000 BTU's in a ton of refrigeration
✔✔Dry-Type Evaporators - ✔✔Are dry because all the liquid is boiled away before
leaving the coil, normal evaporator superheat is 8 to 12 degrees Fahrenheit
✔✔Temperature Ranges - ✔✔High temp- 47- 60 degrees, Medium temp- 28 to 40
degrees, Low temp- -20 to 0 degrees
✔✔Wastewater Systems - ✔✔Isn't economical because water in these systems is used
once and then "wasted" down the drain, but they are more efficient than air-cooled
systems, is only acceptable if its a small amount of water being used.
✔✔Cooling Tower - ✔✔Is a extra device that passes outside air over liquid refigerant to
remove the systems heat, can usually cool the refrigerant to the condenser 7 degrees F
of the wet bulb temperature of the outside air.
UPDATED QUESTIONS AND ANSWERS SURE A+
✔✔Evaporator - ✔✔Absorbs heat into the system, and turns the liquid refrigerant from
the metering device to a vapor. Must be a temperature that is cooler than the air to be
cooled, usually 10-20 degrees cooler in refrigeration and 35 degrees F cooler in air
conditioning,
✔✔Compressor - ✔✔Pumps heat through the system, and reduces the pressure on the
low pressure side of the system and increases the pressure on the high pressure side
✔✔Condenser - ✔✔Rejects heat, and take the high pressure gas from the compressor
and turns the refrigerant into a liquid which gives off heat to the outside air, should be
30 degrees warmer than the outside air
✔✔Metering Device (Expansion Device) - ✔✔Holds back the flow of refrigerant only
pure liquid must enter it but is restricted, it creates flash gas
✔✔Reciprocating Compressor - ✔✔Uses a piston in a cylinder to compress the
refrigerant and valves make sure the refrigerant is flowing in the right direction
, ✔✔Rotary Compressor - ✔✔Uses a rotating drum-like piston that squeezes the
refrigerant vapor out of the discharge line, Typically used for applications on smaller
equipment like window air conditioners.
✔✔Scroll Compressor - ✔✔The movable parts orbit inside the stationary scroll and
squeezes the vapor from the low pressure side to the high pressure side between the
movable stationary parts, and is then discharge in the center of the spiral stationary
scroll
✔✔Compressor Ratio - ✔✔Add fifteen to each side and divide high pressure from low
pressure usually 10:1 refrigeration and 3:1 in air conditiong
✔✔Charles Law - ✔✔By reducing the volume in a cylinder you increase the temperature
of the gas
✔✔Saturated Vapor - ✔✔Occurs when the liquid is all boiled away to a vapor and it is
saturated with heat, but if heat is taken away it will turn back to a liquid
✔✔Flooded Evaporator - ✔✔When a evaporator is operated full of liquid refrigerant and
are equipped with a device that prevents the liquid from entering the compressor.
✔✔Starved Coil - ✔✔When the metering device isn't feeding enough refrigerant to the
coil
✔✔BTU (British Thermal Unit) - ✔✔Is the amount of heat required to raise the
temperature of 1 lb of water 1 degree F. 1 watt = 3.412 btu's, 3,412 btu= 1 KW. There
are 12,000 BTU's in a ton of refrigeration
✔✔Dry-Type Evaporators - ✔✔Are dry because all the liquid is boiled away before
leaving the coil, normal evaporator superheat is 8 to 12 degrees Fahrenheit
✔✔Temperature Ranges - ✔✔High temp- 47- 60 degrees, Medium temp- 28 to 40
degrees, Low temp- -20 to 0 degrees
✔✔Wastewater Systems - ✔✔Isn't economical because water in these systems is used
once and then "wasted" down the drain, but they are more efficient than air-cooled
systems, is only acceptable if its a small amount of water being used.
✔✔Cooling Tower - ✔✔Is a extra device that passes outside air over liquid refigerant to
remove the systems heat, can usually cool the refrigerant to the condenser 7 degrees F
of the wet bulb temperature of the outside air.
