Home > Flashcards > Print Preview
The flashcards below were created by user
on FreezingBlue Flashcards. What would you like to do?
- author "me"
- tags "Hvac 101"
- description ""
- fileName "Hvac terms"
- freezingBlueDBID -1.0
- Is one of the smallest particles of matter.
Is everything that has mass and occupies space.
Is the smallest amount of a compound that can still exhibit the properties of that compound.
Is the smallest bit of an element that will retain the properties of that element.
When an orbital electron is removed from an atom.
Substances that permit the free motion of a large number of electrons.
- * Copper wire is a good conductor b/c it has many free electrons.
- * the size and type of materials used to make the wire in an electric circuit are chosen to keep the electrical resistance as low as possible.
- * the electrical resistance of the wire depends on:
- - the length of the wire
- - the diameter of the wire
- - the material of which the wire is made ( copper, aluminum, etc.)
- Substance that contain very few electrons are called poor conductors, nonconductors, or insulators.
- Every material offers some resistance, or oppositions, to the flow of electric current through it. Good conductors, such as copper, silver, and aluminum, offer very little resistance. Poor conductors, or insulators, such as glass, wood, and paper, offer a high resistance to current flow.
The existence of such an electric force, where current cannot flow, is reffered to as static electricity, or an electrostatic force. Static means not moving.
- The amount of attracting or repelling force that acts between two electrically charged bodies in free space depends on
- * the strength of their charges
- * the distanc between them
The space between and around charged bodies in which their influence is felt
Electomotive force (EMF)
- The force that cause free electrons to move along a conductor as an electric current is called an
- * electromotive force, voltage, difference in potential
Flow of electrons
Electrons flowing in an electric circuit or component
The opposition to the flow of electrons
Direct Current (DC)
- An electron flows only in one direction
- Ex) batteries - mostly used in electronics
Alternation Current (AC)
- Electron flow that flows in one direction and then reverses at regular intervals
- Ex) house power, office power
The number of currents alternating at different times in an alternating current circuit
- The number of complete cycles per second of alternating current;
- A unit of measure of electrical "FREQUENCY"
The difference in electric potential between two points.
- The unit of measure for electrical resistance.
- The amount of resistance that will allow one ampere to flow with the pressure of one volt.
- The unit of measure for electrical current flow.
- The amount of current required to flow through a resistance of one ohm with a pressure of one volt.
- The unit of measure for potential difference or electromotive force.
- The amount of electrical pressure required to force one ampere through a resistance of one ohm.
- Voltage / potential
- Currenct / flow
- Resistance / obstacle to flow
A switch always install on hot leg side not on nuetral leg side.
British Thermal Unit (BTU)
- Quantity of heat required to raise the temperature of one pound of water one degree fahrenheit
- Measurement of heat / 1ton unit equires 12,000 BTU
- The unit of measurement for power ( rate of doing work)
- Volts * amps ::: watts
- 1000 watts :::: 1 kilowatt / 1 kw
- 1 watt will. Generate 3.413 BTU'S
- power is measuring in watts
- Power:::::: energy consumed
- Form of energy that cannot be created nor destroyed, but can be transeferred from one substance to another
- Energy associated with the random motion of molecules
- Absolute zero ::::::: - 460F all molecules are stopped moving
A complet path for the flow of electrons in a circuit or a component
- A device that is used for the path of current flow (usually wires)
- Most electric conductors are copper or aluminum
Electric device that consumes electricity to do useful work, such as motors, relays, and light
Measurement of the intensity of heat
- A device that starts with a large amperage draw and reduces it as the load starts normal operation
- Amperage reduces due to inductive reactance when megnetic field build up
- Ex) anything has coil of wire inside
- A device that maintains a constant current draw as long as the voltage remains constant
- Ex) electric heating element, water heater element, etc.
The relationship between current, electromotive force and resistance in an electric circuit
- E : electromotive force (voltage)
- I : intensity (current in amps)
- R : resistance
- An electric circuit that has more than one path for current to flow
- Ex) control individualy
- Ex) one switch controls three lights
A electric circuit that only has one path for electron flow
A complete path for current to flow
Interrupted electrical circuit that stops flow of electricity
A device for making, breaking, or changing the connection of an electric circuit
SPST, SPDT, DPST, DPDT
- Electrical device that can be energized or de-energizd in one circuit throught which another circuit can be open or closed
- Current flows through a coil, the iron core is magnetized changing position of the contact points
Relays vs. Contactors
- Relays control light amps or loads.
- contactors control heavy amps or loads.
- A device used to increase or decrease the incoming voltage to the desired voltage.
- Transformer has primary coil side (240, 208, 120, volt)
- Secondary coil side (24 volt) output
- Step-up and step-down transformers
- Consist of a layer of insulation; dielectric; placed between two plates of highly conductive metal
- Rated by farads
A circuit that controls some loads in the entire control system, whether it is a relay, contactor, sequencer, etc.
A device that breaks a circuit when the amperage rating is exceeded; constructed of two ends or conductors with a piece of wire that will melt and break the cicuit
A device used as disconnect switch and overload protection for the circuit it is supplying power
Circuit breaker panel
An electric panel that houses circuit breakers used to distribute line voltage power to circuits in a structure
- The voltage being supplied to the equipment as the power supply.
- Ex) 120 volt or 240 volts for residential
A troubleshooting technique for electric circuit that is accomplished by jumping from one component to another
- R - 24 volt hot
- C - 24 volt common
- W - hating ( relay, gas valve, sequencer)
- Y - cooling ( contactor)
- G - indoor blower ( fan relay)
An elctrical diagram that shows the order of electrical devices in an electrical circuit
Three general types of hazards associated with electricity
- Electric shock
- Related accidents
The current that makes a person unable to relase a circuit is extremely small. It can take as little 5 mA to cause the inability to let go.
*** do not bypass fuses
The condition marked by the rapid, uncoordinated twitching of the heart muscle, resulting in a lack of circulation and pluse.
GFCI ( ground-fault circuit interrupter )
A circuit breaker that disconnects the load from the power source when activated by a line-to-ground current other than that carried by the neutral wire.
Lockout / tagout procedure
- 1. Notify to people
- 2. Turn off the power and attach the lockout device
- 3. Put your own padlock
- 4. Tag the equipment with appropriate warning signs
Fires are classified as three types:
CLASS A = an "ordinary" fire that involves the burning of wood, paper, or textile products. A wetting/cooling type of extinguishing agent (water) should be used.
CLASS B = a fire that contains oil, grease, paint, varnish, or other chemicals. A smothering agent (foam) is required for extinguishing this type of fire.
CLASS C = an electrical fire. A nonconducting agent, such as carbon dioxide ( CO2 ), is required to extinguish this type of fire.
Note: since CO2 is monconductive it is the safest to use in terms of electrical safety. Also offers the likelihood of damaging equipment. However, it is dangerous to human life. When it replaces oxygen in the air to the extent that combustion cannot be sustained, respiration also cannot be sustained. Exposure of a person to an atmosphere of high concentration of CO2 will cause suffocation.
Set of contacts or other electrical device that are closed when the device is de-energized.
Set of contacts or other electrical device that is open when the device is de-energized.
Circuit that allows current to flow.
Circuit in which current flow has been interrupted.
- Open: infinie resistance
- Shorted: lower resistance than normal
- Grounded: resistance to ground
- Voltage check
- Amperage checks. (Amperage should not over draws than it designed. Refer to the tag.)
- Never read across a switch.
- Always check supply voltage first or Load.
- Hop through electrical circuit switches.
- Normall switches are in L1 power supply.
- Switches can be in L2.
- All wires must tie in the box/device.
- Lights never install in series but onlt in parellar.
- Nuetral wire never ties and to the switchdirect. It will short the circuit breaker.
- Lights never put in series, only in parellar.
- Netral does not go to the switchdirectly.
- If so, it will short the curcuit breaker.
Most of the switches should not be drawed more than 1 ohm resistance. If so, it will effect to the current voltage.
- Electromagnets are composed of a coil of insulated wire wound around a soft iron core.
- When current flows through the coil, the core becomes magnetized. When the current ceases to flow, the core loses most of its magnetism.
- Ex) motors, relays, contactors, thermostat, solenoid valve, etc.
- - most are 24 VAC control.
- - 24 VAC thermostats are safer and less expensive to install.
- - electric baseboard heat often uses line voltage thermosat.
- Ex) old thermostats ( mercury type )
- Bimetal= close on rising for cooling
- Close on drop for heating
3 - phase AC
- It is 3 * 120 V wires ( hot leg )
- 3 pole breaker
- Ex) domestic = single phase with 120/240 V
- Commercial/industrial = three phase with 120/240 V
- Commercial/industrial = three phase with 120/240 V or 277/480 V
Raise up the voltage to send long distance, that reduce the current.
Add small amount of heat to the thermostat.
- Ammeter - measures current flow (amps)
- Voltmeter - measures voltage (volt)
- Ohmmter - measures resistance (ohms)
- With power on, read voltmeter or ammeter
- With power off, read ohmmeter. also the component itself needs to be isolated from the unit; disconnect.
Components of a complete electric cicuit
- Power source,
- Connecting wires,
- Switch or control
12 FLA @ 120 V
12 flow load amps at 120 V
Difference between relay and contactor
Current carrying capacity
Note) relay has more than one set of contacts
Do not install receptical in series but only in parellar. B/c voltage will drop if it is in series connection.
Armored cable (BX) or (AC)
- - fabricated assembly of insulated conductors in a flexible interlocked metallic armor.
- - sizes #14 gauge thru. #1 gauge in copper.
- - typically used for gas or oil furnace installation (#12 gauge).
- - voltage rating: 600 V or less.
- - support with staples, straps, hangers ever 4 1/2 feet and within 12 inch of every outlet box, junction box or fittings.
- - boxes & fittings: anti short bushing or redeye's used to protect wire from cuts or abrasions used in conjunction with a fitting or connectors.
- - boxes shall be metallic.
- - it is permitted only in dry location.
- - internal bonding strip is not for grounding wire but used to help secure the redeye or bushing from falling out.
- - The metallic enclosure serves as the ground.
Service entrance cable (SE Cable)
- - single or multi-conductor assembly provided with an overall covering, primarily used for services.
- - sizes: #14 and larger in copper.
- - voltage rating: 600V
- - Support with straps every 12 inches of a connector or box, every 4 1/2 feet horizontal or vertical.
- - use permitted in dry or wet locations.
- - sunlight resistance and flame retardant covering above ground only.
- - typically used on outdoor unit or air handling units for heat pump.
UF = Under ground - feeder
- * Factory assembly of insulated conductors with an integral or an overall covering of nonmetallic material suitable for direct burial in the earth.
- * sizes in #14 to 4/0
- * voltage rating: 600 V
- * used permitted: dry or wet locations,also it can be used in underground (sunlight resistance)
- * support with staples or straps every 4 1/2 feet and within 12 inches of junction box of disconnect. Typically used on outdoor unit and indoor air handlers.
Romx (non metallic) wire
- * Non-metallic sheathed cable which is a factory assembly of two or more insulated conductors enclosed within an overall nonmetallic jacket.
- * The overall covering shall be moisture resistance and flame retardant (used in dry location only).
- * sizes in #14 thru. #10
- * voltage rating: 600V
- * support with staples or straps every 4 1/2 feet and within 12 inches of junction box or disconnect. Typically used in house wiring.
Bushing / chase nipple
- Device that prevents abrasion to the conductors as they pass into the apperatus.
- - used on switch boxes that are conncted to the side of the furnace.
Max. Allowable ampacities - copper conductor
- #14 awg - 15 amps
- #12 awg - 20 amps
- #10 awg - 30 amps
- #8 awg - 40 amps
- #6 awg - 55 amps
- #4 awg - 70 amps
- #2 awg - 95 amps
- #1/0 awg - 125 amps
- * Grounded conductor is neutral.
- * Grounding conductor is the ground wire.
Electrical box fill notes
- At least 6 inches of free conductor shall be left at each outlet, junction and switch.
- Unused opening in boxes and encloseures must be closed.
NEC NOTES FOR HVAC
- * Re-identifying the white wire if it used as hot conductor.
- * a 125 volt 15 or 20 amp receptacle outlet shall be installed within 25 feet and on the same level as the outdoor air conditioning equipment.
- (Any outdoor receptacle must be weatherproof or GFIC protected.)
- * Ground-fault circuit interrupters trip when the current to ground is 4mA to 6 mA.
- * In residential homes it is required in bathroom, garages, outdoors, crawl spases, unfinished basements, kitchens, or where the recepticle is within 6 feet of the outside edge of a sink.
- * Any line voltage connections must be installed in a completely enclosed box which could be a junction box, electrical control panel, disconnect, sub panel.
- * Any open knockout holes must be plugged.
- * An air handler does not require a separate disconnect if the breaker panel is within 50 feet of each other. Most air handler require "copper conductors only".
- * When connecting two conductors of dissimilar metals, an oxide inhibitor must be used.
- * If installing a sub panel for an air handler with electric heat, it must be maked on the outside of the sub panel "240 volts only". Also the ground bar must be bonded to the panel with the bonding screw that comes with the sub panel.
- * You cannot clip off some of the strands of wire to make it fit because the wire is too big to fit.
- * If an air handler is installed in attic, it is requird by code to have a light and a receptacle. It requires a light and a GFCI receptacle if it is in crawl space.
- * Can only be sized to handle 80% of max. Load.
- * Any distance over 100 feet, the wire must be resized to handle a voltage drop.
Cicuit breakers and fuses
- * Must be HVACR rated due to inductive loads.
- * Sized by 175% of max. Current draw of the load on inductive loads.
- * 125% on resistive load (electric heater)
- * They ignored the initial inductive starting current of motors and compressors.
- * Used to protect wire from drywall screw and nail.
- * 1/16 inch thick and 16 ga. Steel
- * Not necessary if the wire is run 1 1/4 inch thru. Stud front and back.
- The purpose of this conductor is to prevent electrical shock by prviding a dirct (low resistance) path to earth ground if a ground short occurs.
- Color code: green, bare, green with yellow stripe.