206-Components Flashcards
What five devices are used to measure changes in temperature
Bimetal, fluid expansion, thermocouple, thermistor, hydraulic
What four things do you have to know to buy a replacement control transformer
VA rating, size, primary voltage, secondary voltage
What are the electrical characteristics of most residential transformers
Electrical devices that produce electrical current in a secondary circuit through electromagnetic induction
What are the three types of mounts for transformers
Foot, hub, plate
What does a fan control center consist of
Transformer, indoor fan relay, low-voltage terminals
When would you need to phase 2 transformers
When you have a transformer in the furnace and a separate transformer in the AC system
What is the purpose of the heat anticipator
To prevent or reduce overshooting the temperature setting
When is the heat anticipator in the circuit
While the system is an operation, and it energizes anytime the thermostat Contacts close
What current is used to set the heat anticipator
Set the anticipator to the amp draw of the heat controller
What three things can be used to find the heat anticipator setting
Ammeter with jumper wire, Digital milliamp meter, manufacturers literature
On new digital thermostat is what takes the place of the heat anticipator
Cycle rate settings
What is the purpose of a cooling anticipator
To turn the system on ahead of time, so it doesn’t get hot in the conditioned space before the unit turns on
When is the cooling anticipator in the circuit
When the system is in the off cycle
What are the differences between line voltage and low-voltage thermostats
Line voltage operates with 120 V and above, low-voltage operates with 24 V
What are some applications of line voltage thermostat’s
Refrigeration systems, gas-fired unit heater, electric baseboard heaters, PT AC’s, ventilation fans
What are two types of motor protectors
Fuses, circuit breaker’s
How will a compressor ohm out from common to run when the internal overload opens
OL
How will a compressor ohm out from common to start when the internal overload opens
OL
How will a compressor ohm out from Run to start when the internal overload opens
Will read resistance
What should you do if the internal overload opens
Wait until the compressor cools down, or seal up electrical components and run water over the compressor to cool it down
Gift for uses of a pressure switch that brakes on a fall
Condenser fan cycle control, low pressure cut out control, low charge protection, cycle compressor on a pump down control system
List five reasons a high-pressure switch with open
Dirty condenser coil, fan out, fanblades wrong direction, overcharge, high heat load
What are the two connections of an oil pressure switch
Oil pump outlet, crankcase
What are the three uses of air pressure switches
Ice build up on the outdoor coil of a heat pump, ensure that the blower is passing air through the duct, prove combustion blower motor is operating
What is the purpose of a programmable thermostat
Set up days of the week, times for running, schedule the operation of the systems unit
What maintenance should be done on thermostats
Change batteries if needed, check heat and cooling anticipator
Why are staging thermostats used
Stage on compressor or heat strips depending on the heat or cooling load (save money because of changes in building a load)
Why are two stage heating thermostats used with heat pumps
Heat pumps aren’t efficient below a certain temperature so you need a two stage heating thermostat to bring on either strips or furnace to make up for the heat pump
What are the two differences between a relay and a contactor
Relay handle small loads and is a throwaway, contactor handles larger loads and can be rebuilt
A relay or contactor consists of what three parts
Coil, contacts, terminals
What do the terms normally open and normally closed mean in reference to switches
When do you energized it will either be normally open or normally closed
What four things do you have to know to buy a replacement contactor
Voltage rating, amp rating, coil voltage, mounting arrangement
What is the difference between a contactor and a starter
Contactor has no overload protection, starter has overload protection built in
How are contacts cleaned
They may be buffed or cleaned with a file or sandpaper, this is a temporary solution
How can dirty contacts be detected with a voltmeter
You can use a voltmeter to check resistance across a set of contacts on your full load. When laser place on each side of a set of contacts in a measurable voltage exists there is resistance in the contacts. When the contacts are new and have no resistance no voltage should be read
What is another good way to check contacts
Visual inspection looking for pitted contacts
What are three types of motor protection
Internal external magnetic
What is another name for a magnetic overload
Heinemann overload, Circuit overloads protection
