Oil, Gas Fired, And Electric Heating Systems Flashcards
Learn the basic operating procedures of all types of furnaces, to include boilers.
Since 1992, the United States Department of Energy has required that all furnaces sold and installed from that date on must have an AFUE of no less than:
78%
Many pre-1992 furnaces have efficiencies around _______.
60%
Today, furnaces with AFUE ratings greater than _____ are available.
90%
A thermocouple is used with:
Standing pilot ignition systems
The purpose of the gas pressure regulator is to:
Maintain a constant gas pressure at the burner
The instrument used to measure outlet gas pressure is the:
Monometer
The regulator on a natural gas furnace should be adjusted to supply _____ inches of pressure at the burners.
3.5
Burning 1 cubic foot of natural gas releases approximately _____ Btu
1,050
Under ideal conditions natural gas has an ignition temperature of _______ and a burning temperature of ________.
1,100°F, 3,500°F
(T/F) Propane and butane are both heavier than air.
True
In order to achieve complete combustion with natural gas, each cubic foot of gas must combine with no less than ______ cubic feet of air with an additional 5 cubic feet of extra air to ensure there is enough oxygen for complete combustion.
10
The three elements of combustion are fuel, oxygen, and ____.
ignition
(T/F) Water vapor is a natural result of combustion.
True
Primary air is air that is mixed with the fuel before the fuel ____ the burner.
reaches
Secondary air is air that is mixed with the fuel at the ___ after the fuel is ignited.
burner
The three major furnace configurations are:
Upflow, downflow, and horizontal
Residential gas furnaces use blowers powered by which types of motors?
Split-phase, induction start-induction run, and variable speed DC
The horsepower range of residential heating blower motors is:
1/4 to 1/2 hp
A heat anticipator is wired:
In series with the W terminal
Placing a jumper wire between the R terminal and the G terminal on a thermostat subbase will energize the:
Indoor fan motor
Placing a jumper wire between the R terminal and the W terminal on a thermostat subbase will energize the:
Gas valve
Carbon monoxide is a(n):
Product of incomplete combustion
Poisonous gas
Odorless gas
The chemical symbol for carbon monoxide is:
CO
Selecting a lower speed tap setting on a furnace indoor blower motor will cause the:
temperature rise through the furnace to increase
Carry over channels or cross overs are used to carry:
the flame from the first burner that lights to the remaining burners
Modern high-efficiency burners use combustion blowers. What are the two major types of combustion blowers?
Induced draft and forced draft
The purpose of the combustion blower is to:
Cause an adequate amount of oxygen-rich air to mix with the fuel for better combustion
Heat transfers from an object or area at a higher temperature to an object or area at a lower temperature. A heated heat exchanger transfers heat to the air by:
Forced convection
The voltage that creates a spark on a spark ignition system is approximately:
15,000 volts
The capacity of a natural gas furnace is de-rated by _______ for every 1,000 feet above sea level:
4%
A crack in a heat exchanger can:
Allow combustion gases to mix with the space air
Gas valves operate on what voltage?
24 volts
Mid-efficiency furnaces operate with flue gas temperatures between:
275°F and 360°F
High-efficiency furnaces operate with flue gas temperatures between:
100°F and 275°F
A “B” vent is a:
Double wall sheet metal vent pipe
Latent heat is:
Both heat that causes a change in state with no change in temperature and the large amount of heat involved when a gas condenses into a liquid
A mid-efficiency or high-efficiency furnace will not operate if:
It is not grounded or the polarity is reversed
Furnaces are placed into categories based upon:
Venting characteristics
Condensing furnaces:
Squeeze additional heat out of the flue gases by removing the latent heat of condensation from the gas and causing much of the gas to liquefy
Secondary heat exchangers are:
constructed so the return air passes over the secondary heat exchanger first and then passes over the main heat exchanger
A combination fan-stat and high limit:
Are separate switches operating off a single helical bimetal with one switch controlling the indoor fan and the other acting as a high temperature safety control
The three basic categories of ignition systems are:
Continuous ignition, intermittent ignition, and direct ignition
The intermittent ignition system:
Lights the pilot only on a call for heat
Direct ignition:
Uses a spark or hot surface igniter to light the burner directly
The flame sensor is a:
small-diameter conducting rod that senses when a flame is present because a current flow moves between the rod and the burner when the flame creates an electrical path between them
What is a typical sequence of operation for a high-efficiency condensing furnace?
Upon a call for heat the induced draft blower starts and runs for 20 seconds, the ignitor heats up for 15 seconds, the gas valve opens, the burner lights off, and the flame sensor detects and monitors
A yellow burner flame is usually caused by:
Lack of sufficient air
A lifting burner flame is usually caused by:
High gas pressure and/or too much primary air
What is the purpose of timing a gas meter?
To determine the actual input in Btuh of the furnace
Electrical troubleshooting of a furnace is best accomplished with:
Both a pictorial wiring diagram and a voltmeter
What is the density of untreated water?
8.33 pounds per gallon
Combustion is the rapid union of _____ with an element or compound that results in the release of heat.
oxygen
The three types of combustion are:
perfect, complete, and incomplete
What is 9 psig converted to psia?
- 7
* psig to psia add 14.7
* *psia to psig subtract 14.7
A low pressure steam boiler is a boiler operated at pressures not exceeding _____ psi.
15
A low pressure hot water boiler is a boiler which heats water to temperatures not exceeding _____ and a pressure not exceeding 160 psi.
250 degrees F
Fuel, heat, and _____ are required to start and sustain combustion.
oxygen
All steam boilers operate using a _____ system, fuel system, draft system, and steam system.
feed water
Heating coils located in the conditioned space and piped in series:
Have a ____ resistance of flow ____ to the sum of their individual resistances
Loses water ____ as the water passes through each coil
Are ____ ideal for for good comfort control
- total, equivalent
- temperature
- not
Steam at 14.7 psia at a temperature of 225 degrees F is:
superheated
Liquid water at 14.7 psia at a temperature of 190 degrees F is:
subcooled
What heat piping systems has the same length in linear feet from the boiler to each of the heating coils and back to the boiler?
Reverse return piping
Heating water in an enclosed vessel:
raises its saturation temperature
What is often used to support pipe?
Clevis support and hanger
The use of an expansion loop or piping offset in piping is to:
allow for expansion and contraction
The wall thickness of black steel pipe is referred to by its _____ number.
schedule
The wall thickness of copper tubing is listed by its:
lettering system
Steel pipe with a coating of tin on the surface is called _____ pipe.
galvanized
What valve type is best for stopping and starting flow?
Gate valve
Which valve type should not be used for regulating flow?
Gate valve
What three functions does a triple duty valve serve?
Check, balancing, and shut-off
Which pump is supported by its piping?
In-line pump
In a hydronic system installation, the point of no pressure change takes place at the:
expansion tank
The accumulation of high alkaline elements which cause boiler metal corrosion at stress zones is called _____.
caustic embrittlement
A mixture of salts or glycols with water to reduce the freezing point of the water results in a liquid mixture called:
brine
Spacing of pipe supports is a function of pipe size and _____.
material
Which of the following piping system types requires the least amount of balancing?
Reverse return
Series loop heating coils can be provided with _____ fittings to improve flow control and lessen water temperature drop.
monoflow
In-floor hydronic heating heats a room primarily by:
radiation
Steam and hot water boilers must be fitted with:
a low water cut-off control
Locating a heating valve at the outlet of a coil is often preferred so that it:
- operates cooler
- is subjected to lower pressure
- has more authority
A check valve placed in a vertical pipe should be:
a spring check
The main concept behind the condensing boiler is the capture and use of _____ heat to increase boiler efficiency.
latent
Typical stack dew point temperatures in a boiler range between:
120 and 140 degrees F
Galvanized steel flue pipe should never be used with:
condensing boilers
Hanging pipe supports are to be placed at what maximum distance for copper pipe 3/4 inch in diameter and smaller?
5 feet
What is the feature of a baseboard tee?
Has an FTP port for accessories
Which piping system uses the same coils and valves for both heating and cooling?
Seasonal two-pipe switchover system
To minimize the possibility of a boiler burner fuel explosion, the boiler goes through a(n):
pre-purge cycle
The amount of draft produced by a chimney depends on:
its height and temperature difference
Mechanical draft is used when burning:
coal,fuel oil, natural gas
When a thermocouple is heated:
a voltage is produced
The specific heat of water is _____ BTU.
1.0
The latent heat of vaporization value for water at 0 psig is _____ BTU per pound.
970
One pound of water is needed to produce _____ pounds of steam.
1.0
What device relieves excess pressure when a solder core melts and causes an audible alarm when exposed to its maximum permissible temperature
Fusible plug
Boiler water is treated to prevent:
oxygen pitting, scale, caustic embrittlement
Burning a fuel releases:
heat energy
The device which provides the power to move a valve is the:
actuator
What electro-mechanical control would you use on a cap tube or automatic expansion valve system to maintain the space temperature?
A thermostatic control
Open motors are designed to operate at a given temperature rise as indicated on the motor nameplate. What does this mean?
It indicates the temperature rise over the surrounding air of a motor when the motor is operating at full-load conditions.
A voltmeter is connected into a circuit in which of the following ways?
Parallel
A low pressure control is usually located on the:
Condensing unit
A high pressure control is usually located on the:
Condensing unit
The term “nominal voltage” refers to the:
listed voltage
Low voltage controls are usually designed to operate at no more than:
≤25 volts
A unit of power equal to 1 horsepower and delivered at the shaft of a motor is known as:
Brake horsepower
What is the purpose of the holding circuit in a magnetic motor starter?
Holds the main contacts closed until the control circuit through the interlock is broken
On a magnetic motor starter, the alloy piece that causes the motor starter to open and shut off the motor if too much motor current is drawn is called the:
Trip armature
A set of contacts in a pressure control that close when the pressure increases are:
Direct acting
Which of the following control settings is typically non-adjustable?
Set point, Differential,Cut-in, Range
Range
Ohm’s law states:
E = IR
The run capacitor on a motor is used to:
Increase torque
Doubling the voltage to a resistance will cause the power or watts to:
Quadruple
What is impedance?
Opposition to alternating current flow
How are fuses sized?
By both amperage and voltage
Capacitors are rated in:
Both microfarads and volts
One horsepower is equal to _______ watts.
746
How much resistance must be placed in a 220-volt circuit to limit the current to 2 amps?
110 ohms
E = IR thus R = E/I
Impedance in a circuit is the result of:
Pure resistance, Inductive reactance, Capacitive reactance
Doubling the voltage to a fixed resistance will:
Cause the current to double
When the temperature of a negative temperature coefficient material increases, its resistance will:
Decrease
What is the Btuh output of an electric heater rated at 15 Kw?
51,150 Btuh
1 watt = 3.412142 BTU/hr
What is the total capacitance of two 20-microfarad capacitors wired in series with each other?
10 mf
Capacitance from capacitors wired in series are always less then the sum of the two.
C total = 1 / (1/C + 1/C2 + 1/C3 …)
What is the total capacitance of two 20-microfarad capacitors wired in parallel with each other?
40 mf
Capacitance from capacitors wired in parallel is equal to the sum of the capacitors rating.
C total = C1 + C2 + C3 …
If a conductor is wrapped around the jaws of a clamp-on ammeter four times and the meter indicated 16 amps, the actual amperage would be:
4 amps
Actual amp draw on a clamp meter is equal to the # of wraps / meter reading
On a standard electro-mechanical thermostat, if the fan switch is in the “on” position, the indoor fan will run:
continuously
A motor is a ________ load.
inductive
The compressor oil safety control is an electro-mechanical control that operates on which two pressures?
Oil pump pressure and suction pressure
What is the millivolt reading of a good thermocouple?
15 mv
A high pressure safety control is:
Reverse acting
Two silicon-controlled rectifiers wired in reverse parallel with each other allow current to flow:
in both directions
Hot surface igniters operate on which of the following voltages?
120 volts
Which of the following mathematical relationships is true of a motor’s horsepower if the cfm of a blower were changed?
Hp changes by the cube of the change in cfm.
When four diodes are constructed in a bridge circuit and alternating current is brought into the input of the bridge, the output of the bridge provides:
Full-wave rectification
When photons of light strike the surface of a typical cadmium sulfide photoconductive cell, _____.
resistance decreases
The coil of a lockout relay is wired in ________ with the contactor coil and in ________ with the contacts of the control it is protecting.
series, parallel
A low-voltage control system that primarily operates on two levels of voltage is called a(n):
digital system
A voltage imbalance is a problem associated with which type of motor?
Three-phase motors
An air conditioning compressor has the following motor protection devices: low-pressure control, high-pressure control, internal thermostatic overloads, and an oil failure control. If the internal thermostatic overloads open, which of the following will take place?
Oil-failure control will trip off and lock out the compressor.
What is the purpose of the resistor wired across the terminals of a start capacitor?
To prevent arcing and possible damage to the start relay contacts
Which of the following will cause an increase in the horsepower required per ton of cooling on an air conditioning system?
Increasing discharge pressure and decreasing suction pressure
Using an automatic pump-down system, the compressor is directly controlled by:
Low-pressure control
70 degrees Fahrenheit is equivalent to _____ degrees Celsius.
21 degrees Celsius
Formula: C = (F - 32) * 5/9 or (F - 32) * 0.56
28 degrees Celsius is equivalent to _____ degrees Fahrenheit.
82 degrees Fahrenheit
Formula: F = (C * 9/5) + 32 or (C * 1.8) + 32
On a low pressure residential steam boiler the relief device opens at?
15 pounds
If to much primary air is used the flame will _____?
Lift off of the burner
What operates the heat anticipator in a low voltage thermostat?
24 Volts A/C
A limit control is located where in the electrical circuit?
Either the 24 or 120 volt circuit
What is the usual oil pressure at the nozzle in a high pressure gun type oil burner?
100 psig
The amount of 3/4” copper that holds approximately 1 gallon of water is?
43 feet
A psychrometer is a ___________________?
a hygrometer consisting of a wet-bulb and dry-bulb thermometer. The difference in the two readings is used to determine the atmospheric humidity
A psychrometric chart is a _______________?
chart where various properties of air are plotted
Combustion is what type of process?
Chemical
What percentage of oxygen is in the air?
21% ish some say 23%
A hand shut off valve in a gas line is used to turn gas on and off to _____.
burner and pilot
CGV is the abbreviation for _________?
combination gas valve
The maximum safety drop out time for a thermo-couple is _____?
three (3) minutes
The bimetallic strip of metal in a thermostat is made of copper and _____?
invar
Invar is an alloy of iron and nickel with a negligible coefficient of expansion.
What is the light sensitive material used in a cad cell?
Cadmium Sulphide
What is the resistance measured in a cad cell in the absence of light?
100,000 ohms
When operating a fuel oil with a one pipe system, what needs to take place at the fuel pump?
Bypass plug should not be installed
A gas drip leg must ________?
not be smaller in diameter then the pipe which it connects
All boilers shall have the potable water protected with ______?
a back flow preventer
Compared to natural gas with the same Btu/h rating, the orifice opening in an LP gas fire furnace is ______?
smaller
A thermostat that cycles too often or not enough indicates _________?
improper heat anticipator setting
The pressure regulator on a LP gas system is set at _____?
11.0” w.c. some say 10.5
A fast acting type of gas valve is the _____?
solenoid
The air for combustion in a building must be at least one square inch per?
1,000 Btu/h
Which pipe has the thickest wall?
schedule 80
Ducts shall be supported at intervals of _____?
12 feet
Cold air returns in bathrooms should be ______?
omitted
Single wall or Type B vent pipe must have a minimum rise of _____?
1/4” per foot
On a gravity warm air furnace, the limit control setting shall not exceed?
250 degrees
Natural gas burner orifices are __________?
larger in diameter than propane gas burner orifices
The location of outside air exhaust and intake openings shall be located a minimum of __ feet from lot lines or buildings on the same lot.
10
In hvac heating, a standing pilot burns _______?
continuously
A yellow flame in a gas burner indicates _________?
poor air-fuel mixture
Total heat is _________?
sensible heat plus latent heat
How much maximum play is allowed in the blower belt of a forced air furnace?
1”
In maintaining a forced warm air furnace what is the minimum number of times the blower and electric motor bearings should be oiled?
Once each heating season
As the gauge of electrical wires decreases in numerical value the current caring capacity ______.
increases
The thermostat range is the __________?
open and closed settings of the thermostat
A gas fire furnace with a 6” common vent can have what other type of exhaust or vent connected to the vent?
No other exhaust may be connected
A U-shaped tube partially filled with liquid and constructed so that the amount of displacement of the liquid indicates the pressure being exerted on the instrument is a(n) ______?
manometer
In order for oil to burn it passes through a nozzle to be ________?
vaporized or atomized
vaporized or atomized
Compression
Over time they can become loose and start to leak.
Low pressure type oil burners operate at pressures of ______?
1 to 4 psig
The ignition system of an oil system must raise the oil temperature to?
700 degrees Fahrenheit
No part of an electrode inside an oil burner shall be closer then ______ to any metal part.
1/4”
Oil nozzles are based on gallons per hour at ____ psig.
100
The range of carbon dioxide in oil burner flue gas is?
10-12 percent
Which is not a type of electric resistance heating wire? Open Wire Open Ribbon Tubular Cased Wire Straight Wire
Which is not a type of electric resistance heating wire? Open Wire Open Ribbon Tubular Cased Wire Straight Wire
Oil burners use a _______ to prove a flame is present?
cadmium sulfide cell
What type of shut of valve can be installed between a boiler and the low water cut off?
No valves can be installed in this location
What type of license is required to install and repair boilers?
mechanical contractors license and boiler installer license
What is the formula used to calculate a force air furnace supply and return air duct sizing?
2 square inches for every 1,000 Btu output
What would be the most likely cause of a furnace direct drive blower motor that failed for 3 consecutive years and had to be replaced?
Bad duct design causing high static pressure
When a volt meter leads are placed on a thermostat R & W terminals, when there is no call for heat, the voltage should read _____ volts.
24 V A/C
The difference between the supply air temperature and return air temperature on a forced air furnace is known as ______.
temperature rise
What would cause low propane pressure on the outlet of a LP gas regulator during extreme cold temperatures?
low or empty propane tank
restriction in the regulator vent
propane has condensed due to low temperatures
What is the correct sequence for a gas fired furnace with a flame sensor?
The flame signal goes to the control module with relays that send the signal to the gas valve
A gas space heater that operates with no external power source would be operating on
millivolts
What drives the oil pump on an oil fired furnace?
burner motor
A fuel oil furnace in a residential application operates in the range of _____ psi.
100-150
A fuel oil furnace in a commercial application operates in the range of ______ psi.
100-300
Correct pitch for a steam boiler horizontal supply mains and dry returns must be ______ minimum in 10 feet of pipe in the direction of steam and condensate flow.
1/4”
Piping from the top of a steam boiler to maintain pressure balance on water in the boiler return connection is known as the _____?
equalizer
The ______ consists of two loops of piping that acts as a safety device to prevent the water from draining out of the boiler if a leak develops in return piping. First loop surrounds the boiler; second is the balance of the system.
Hartford Loop
In a steam boiler system with a no heat call, if the steam supply line is hot and return pipe is cold the most likely cause would be ___________?
air trapped in the system
What device controls automatic recycling on an oil burning appliance?
Primary Control
The abbreviation “CSD” stand for?
Controls and Safety Devices for automatically fired boilers
All steam boilers must have _____?
Quick shutoff blowout valve
Water glass gauge/pressure gauge
Controls and limit devices required by ASHRE and CSD-1
What best describes an oil ignition transformer?
A transformer that increases the line voltage to create an ignition arc
A boiler pressure relief valve that is dispensing intermittently is most likely caused by _____?
The expansion tank being water logged
The site glass installed mid-point on a boiler is ___________?
to show the normal boiler water level
A gas fired boiler with a Btu rating of 150,000 Btu’s requires _______ per CSD-1 section CW-410.
The limit to be 150,000 Btu’s with a manual reset
What does AFUE stand for?
Annual Fuel Utilization Efficiency
What direction does circulating air travel in a condensing furnace?
The air travels in the opposite direction of condensing gases. First it travels over the secondary heat exchangers then over the primary.
Indoor blowers usually have a hp up to what and are classified as what drive type?
3/4 hp that is either direct drive of belt driven
What are the classifications of combustion blowers?
Induced-Draft (+ psi on the pressure switch) and Forced-Draft (- psi on the pressure switch)
At what temperature does a thermostatic blower control usually turn on and off?
around 140 degrees F and 90 degrees F
Can condensing furnace combustion gases be vented through a chimney?
Yes and no. if the chimney has a liner installed they can. Condensing furnace combustion gases are corrosive and without a liner they will deteriorate a chimney.
For belt-driven indoor blowers, as the size of the pulley on the motor increases, the blower speed _____?
increases
For belt-driven indoor blowers, as the size of the pulley on the blower increases, the blower speed _____?
decreases
The water used in a boiler start up (boiling out) should be tested for what?
hardness, contaminants, and proper pH level
Most hydronic system problems fall into what areas?
Electrical, venting, water
What is the purpose of the air break in some furnace styles?
It helps keep constant pressure in the combustion chamber and prevents back pressure.
What are the typical ignition temperature of LP gas and Natural gas?
LP : 920°F (493°C) and 1020°F (549°C)
Natural: 1100°F (593°C) and 1200°F (649°C)
