Electrical Flashcards
During a power outage a thermopile/powerpile equipped burner in a convection type appliance (space or wall heater) will…
Continue to operate normally
*An open circuit test for a thermocouple should read
A maximum of 30 mvdc and a minimum of 20 mvdc
Minimum operating voltage of a thermocouple before replacing it is…
8 mvdc
A reading of 10-15mvdc across a closed switch on a powerpile system may indicate…
Switch contact is in poor condition
A millivolt system, using 16 gauge wire can have a maximum length of…
50 feet
Drop out reading of 10 millivolts or more indicates…
Defective pilot stat in gas valve
Thermocouple tip should be inserted into the pilot flame…
3/8 - 1/2 inch
Noisy or lifting pilot flame indicates
High gas pressure
Millivolt wiring can’t run near line voltage wiring since…
Line voltage wiring will induce a voltage into millivolt wiring
A thermostat for millivolt systems is rated in
0-1.5 VDC
3 voltage outputs for a thermopile/powerpile
250, 500, 750 MV
Transformers power output(s)
VA and Watts
What does a transformer consist of?
Core of iron plates, primary and secondary winding
Best type of connection for millivolt systems
Soldered connections
Motor starting switch rated in…
Horsepower
Temperature difference needed between hot and cold junction
400 Farenheit
Pilot stat test operation depends on two tests
5 to 2 mvdc, 90 seconds
Another thing to do
Go over reading diagrams
Electrical service is rated in
Amps
Minimum electrical service to a new residential building
100 Amps
Electrical distribution system consists of:
Electric meter, main disconnect, distribution panel
What protection does a 240 volt circuit need in the distribution panel?
Double pole breaker
Overload protection for a 120 volt circuit in the distribution panel
Single pole breaker
GFI is required in…
Wet locations
When is gas piping bonded?
To prevent arcing or sparks
Ultimate purpose of a fuse or circuit breaker in the distribution system
To protect higher amperage from damaging electrical conductors
Circuits powering a motor that is protected by a plug fuse, shall use a
Type P
Electrical conductors are made in
Solid, stranded wire
*Allowable amperage in a circuit using No.14/3 AWG Wire at 60 Degrees Celsius
20 Amps
NMD stands for…
Non-metallic dry
NMW stands for…
Non-metallic wet
Maximum allowable amperage using #10 AWG wire
30 Amps
White wire indicates
Neutral conductor
Wire exposed to mechanical damage must be
AC (BX)
The lower the gauge wire
The more current the conductor can safely carry
Types of wiring diagrams in the gas industry
Pictoral, schematic, connection
Where does the circuit breaker in a 120v circuit supply power from?
Load side of the main breaker
Maximum amperage of a fuse in a distribution panel is limited by
Gauge of the wire
Armoured cable is
BX
Motor circuit protection fuse is a
Time delay fuse
Where does the 240v supply for an electric range come from last
Load side of a double branch breaker
Schematic diagrams show components
Normally de-energized
Direct current travels
In one direction forward
Line and load sides for the disconnect/service switch use what colour for residential furnaces
Both black wires
Electrical conductors when subjected to higher temperatures
Results in lower resistance
Unit of measure for EMF
Volts
Fuses and breakers protect
Wires
Max amps for 12 AWG
20 Amps
Diameter of wire goes up
Resistance goes down
Voltage measured in residential distribution system
240v
3 operating controls
Thermostat, operating aquastat, operating pressure controls
3 safety controls
High-limit switch, pressure switch, flow switch
3 types of pilots in a residential furnace
Standing, intermittent, hot surface igniter
3 main types of automatic ignition control systems in a residential furnace
Intermittent pilot, direct spark ignition, hot surface ignition
3 main components in a combination gas valve
Gas control valve, pressure regulator, pilot
Another name for an air flow switch
Sale switch
Minimum ratio of ground surface area to flame rod surface area for proper flame rectification
4-1
Advantage of a redundant gas valve
Higher safety (second shut-off valve is incorporated) Eliminates the
Safety device used on all storage type water heaters
Temperature and pressure relief valve
3 types of gas pressure regulators
Line pressure regulator, appliance regulator, service regulator
Sequence of operation for CAT 1 Fan Assist Furnace with D.C
Call for Heat, inducer Motor Start, Pressure Switch Check, Ignition Sequence, Flame Sensing, Main Burner Operation, Blower Motor Activation, Thermostat Satisfaction
Basic operation of ignition system
Perform safety check, ignite the flame, powering gas valve, proving flame, monitor flame
SRC, TRIAC, and DIAC are
Thyristors
Primary difference between a relay and contactor
Relay for lower power application, contactor for higher power applications
Relay operates by
Electromagnetic coil
Thermocouple MV range
0-30
Millivolt - Volt
1/1000
Thermopile MV range
Up to 750 mv
Open circuit thermocouple test
Should read 30 mv, below 20 mv must be replaced
Closed circuit thermocouple test
Should read 15 mv, below 8 mv must be replaced
Pilotstat coil MV reading
Under normal operation 10-15 mv, must hold the valve open until 5-2 mv
750 mv thermopile must power…
Control circuit and combustion safety circuit in parallel
30 ft = AWG
18 Min.
50 ft = AWG
16 min.
80 ft = AWG
14 min.
Thermopile = How many thermocouples
10-30
Thermocouples = Which pilot?
Standing
Type of current for thermocouples
DC
Thermostat:
R= 24v power
W= Heating
Y= Cooling
G= Fan
C = 24v Common
YEaaaaaa
Where would you find an operating pressuretrol?
Hot water boiler
Operating pressuretrol responds to changes in
Steam pressure
Heat anticipator is wired
In series w the gas valve
HIgh gas pressure switch opens when pressure is exceeded by
25%
When heated, ignites burners in a furnace
Hot surface igniter
Unitrol is used on
Water heater
Flame rod is made of
Kanthol
Valve for throttling fluid
Globe valve
Redundant gas valve contains
2 automatic gas shut off valves in series
Rod and tube is made of
Invar
