Skills study guide hvac
The temperature on the Celsius scale where all molecular activity stops
-273 degrees
How many chlorine atoms does it take to destroy 100,000 ozone molecules in the stratosphere
1
If a technician needed 5/8" ACR for an installation and was located near only a plumbing supply house, what size and type of pipe should he ask for?
1/2" ID copper
On a 95 degree day, R-22 pressure on the high side of the system should be at
243 psig
A ton of refrigeration is equal to ?
288,000 Btu/24 hr
standard atmospheric pressure at sea level is
29.92 in Hg or 14.7 Psig
how many btus must be removed from one pound of water @ 200'F to end up as ice @ 30'F?
313 BTU
The maximum temperature at which soft soldering is done is
800 degrees F
If large amounts of ice are forming on a low temperature evaporator, what could be the problem
A bad evaporator fan or a faulty hot gas bypass solenoid
Some compressor contractors only have one set of contacts instead of two so that
A small amount of power can be passed through the motor windings for off cycle crank case heat
High temperature refrigeration is produced by
An air conditioning
The fitting at the end of a round duct that connects the duct to the floor register is called a(n) ____.
Boot
Primary air adjusters on atmospheric type gas burners are usually ____.
Butterfly shutters, sliding sleeves, spoiler screws
The human body gives off what type of heat
Convection, radiation and conduction
The starting device on a single phase, fractional horsepower compressor motor is
Current relay
permanent split capacitor motor that is running and up to speed will have the start winding
Energized
The refrigerant in a refrigeration system changes state in the
Evaporator and condenser
A thermostatic expansion valve controls refrigerant flow to the evaporator based on
Evaporator suction line super heat
If there is too much primary air, the gas flame can
Get blown out or lift off the burner rack
The number engraved on the nozzle indicates
How many gallons of oil per hour the nozzle will deliver at a given input pressure
To make combustion efficiency tests, a hole must be made ____.
In the flue pipe before the draft control
The pressure relief valve
Is set to relieve the pressure in the boiler below the designed pressure of the boiler
If a thermostatic expansion valve's thermal bulb came loose from the suction line at the outlet of the evaporator, which of the following could result?
Liquid refrigerant floods back to the compressor, the supper heat would decrease, the bulb pressure would increase and the txv would open
On a package air conditioning unit, what lines must be field installed
None
a motors speed is determined by
Number of motor poles
The expansion tank does what
Provides a means of removing air from the system and provides space for the expansion and contraction of water with temperature
The compressor in the refrigeration system
Pumps the refrigerant throughout the system and raises the bailing point of the refrigerant
Which type of refrigerants is a CFC type refrigerant
R-12
Which of the following refrigerants has the lowest boiling temperatures at atmospheric pressure
R-502
When the oil supply is above the oil burner pump, the pump and supply would normally be a ____.
Single-stage pump, one pipe system
The orifice is a precisely sized hole in the
Spud
In a system using capillary tubes or orifice, when the air filters become restricted, the evaporator superheat will _____.
Surge back and forth or oscillate.
What prevents cold air from being circulated in a heated space during defrost in a heat pump system
The auxiliary heat is turned on to temper the air
If an air conditioning system develops a refrigerant leak and the system doesn't have a low pressure cut off what can happen
The compressor can overheat and air can be sucked into the system
If a technician connects gauges on the line set of the outdoor unit on a heat pump in heating mode, their pressures should read
The high side will read the high side pressure and the low side will be in the RETARD range
What happens when room temperature soda is poured into a glass of ice
The ice melts because it is absorbing the heat from the soda
One reason for using a reducing plenum system is to keep
The velocity of the air consistent and to keep duct pressure constant
The reason for using zone valves on a hydronic heating system is to
To allow different parts of the house to maintain different temperatures and to prevent ghost heat
The law requires technicians to recover refrigerant from all refrigeration systems so that they
Will not be released into the atmosphere, can be used again, may be reclaimed for future use
A technician needs to check a single phase compressor. A to B is 10 ohms. B to C reads infinity and so does C to A. Identify the terminals
You can't. The winding is open
An ampere is
a measure of the quantity of electrons flowing past a point in the electrical circuit in a given time
Temperature is an indication of the
amount of molecular activity in the material
High efficiency condensers
have more surface area than standard condensers
If a conductor carrying electrical current is formed into a coil, the magnetic field around the wire will
increase
When soldering or brazing, the solder is
melted by heat from the tubing and fitting
The start windings have
more turns than the run windings
What type of charge do electrons have?
negative charge
What type of charge does a proton have?
positive
A split-phase motor can use a _______ to energize and de-energize a start winding
potential relay, current relay, centrifugal switch
Refrigeration can be described as
the process of removing heat from a place where it is not wanted to a place where it makes little or no difference
To reprocess refrigerant to meet new product specifications is called ____.
to reclaim
