OBT3 Final Exam Questions and All
Actual Answers 2026 Updated.
Fuel oil is a member of the _______ family of chemical compounds. - Answer Hydrocarbon
Approximately 96% to 99.75% of fuel oil is composed of - Answer Hydrogen and carbon
The two general categories of refined fuel oils are - Answer Distillates and residuals
True or false: kerosine is classified separately from fuel oil but considered as fuel oil under the
fuel oil code - Answer True
0 fuel oil application - Answer Intended for use in appliances in far northern regions
1 fuel oil applications - Answer Used where #w fuel oil cant be used satisfactory
#2 fuel oil applications - Answer Used in most domestic type burners
#4 fuel oil applications - Answer Industrial type fuel for burners not equipped with
preheaters
#5 fuel oil applications - Answer Useed in burners equipped with pre-heaters requiring
greater fluidity of #6 six
#6 fuel oil - Answer Only be employed in burner equipped with pre heaters
Degrees of API gravity is a measurement scale of a fuel oil's - Answer Density or weight
#2 fuel oil has a API gravity range of - Answer 30-36
The commonly excepted heat value of number 2 fuel oil is__________ BTU/us gallon - Answer
140 000
If the input reading of an appliance is 91,000 BTU the correct nozzle size would be - Answer
0.65
,Viscosity is a measure of a fluids - Answer Resistance to flow
A fuel oil's viscosity_____________ (increases or decreases) as the temperature of fuel oil
decreases - Answer Increases
The distillation characteristics of a fuel oil indicates it's - Answer Volatility and ability to
vaporize
T or f. Liquid fuel oil will burn - Answer False
Flashpoint is defined as the lowest temperature and which a few oil will - Answer Vapours
will first ignite when exposed to a flame
Fire point is defined as the lowest temperature at which fuel oil will - Answer There are
sufficient vapours generated by the heated oil
Poor point is defined as the lowest temperature at which fuel oil will - Answer No longer flow
Cloud point is defined as the lowest temperature At which fuel oil will - Answer Wax crystals
begin to form
Sulphur is a - Answer Corrosive chemical compound found in minor amounts in few oil
Name two reasons that water is found in a fuel oil storage tanks - Answer 1) water is heavier
than oil
2) it's a breeding ground for micro scopic bacterial growth
True or false) colour and odour or reliable indicators of the properties and qualities of fuel oil -
Answer False
The products of a complete combustion of fuel oil and air are - Answer Carbon dioxide
The ultimate CO2 from the combustion of number 2 fuel oil and air is - Answer 15.3%
Name three undesirable products incomplete incomplete combustion - Answer Soot, carbon
monoxide, reduced heat
, Carbon dioxide and nitrogen are - Answer Toxic gases
What gas is a inert and passes through the combustion reaction without significant effect except
for absorbing heat - Answer Nitrogen
Describe the symptoms of carbon monoxide poisoning - Answer Headaches, dizziness,
nausea without fever
(True or false) the appearance of a few oil flame specifically it's colour insert production, is the
best indicator of the quality of the combustion process - Answer False
Name the two ways of preparing feel oil for combustion - Answer Vaporization and
atomization
What effect with too small of combustion chamber have on combustion - Answer If the
combustion chamber is too small for firing right flame oil spray impingement and also
incomplete combustion
( True or false)hard fire brick is the best material for combustion chambers in residential
appliances - Answer False
The term combustion efficiency is properly used to refer to eficiency of the - Answer
Combustion reaction
Name the five ways in which heating heating appliance can lose the chemical heat energy of the
fuel - Answer 1. On cycle heat loss
2. Off cycle heat loss
3. Jacket heat loss
4. Distribution heat lost
5. Air infiltration heat loss
Explain on cycle heat loss - Answer Heat loss during an operation of the appliance
Explain our cycle heat loss - Answer Heat loss when an appliance is not operating
Explain jacket heat loss - Answer Heat loss by appliance appliance both on and off
Explain distribution heat loss - Answer Heat loss from ducks or piping
Actual Answers 2026 Updated.
Fuel oil is a member of the _______ family of chemical compounds. - Answer Hydrocarbon
Approximately 96% to 99.75% of fuel oil is composed of - Answer Hydrogen and carbon
The two general categories of refined fuel oils are - Answer Distillates and residuals
True or false: kerosine is classified separately from fuel oil but considered as fuel oil under the
fuel oil code - Answer True
0 fuel oil application - Answer Intended for use in appliances in far northern regions
1 fuel oil applications - Answer Used where #w fuel oil cant be used satisfactory
#2 fuel oil applications - Answer Used in most domestic type burners
#4 fuel oil applications - Answer Industrial type fuel for burners not equipped with
preheaters
#5 fuel oil applications - Answer Useed in burners equipped with pre-heaters requiring
greater fluidity of #6 six
#6 fuel oil - Answer Only be employed in burner equipped with pre heaters
Degrees of API gravity is a measurement scale of a fuel oil's - Answer Density or weight
#2 fuel oil has a API gravity range of - Answer 30-36
The commonly excepted heat value of number 2 fuel oil is__________ BTU/us gallon - Answer
140 000
If the input reading of an appliance is 91,000 BTU the correct nozzle size would be - Answer
0.65
,Viscosity is a measure of a fluids - Answer Resistance to flow
A fuel oil's viscosity_____________ (increases or decreases) as the temperature of fuel oil
decreases - Answer Increases
The distillation characteristics of a fuel oil indicates it's - Answer Volatility and ability to
vaporize
T or f. Liquid fuel oil will burn - Answer False
Flashpoint is defined as the lowest temperature and which a few oil will - Answer Vapours
will first ignite when exposed to a flame
Fire point is defined as the lowest temperature at which fuel oil will - Answer There are
sufficient vapours generated by the heated oil
Poor point is defined as the lowest temperature at which fuel oil will - Answer No longer flow
Cloud point is defined as the lowest temperature At which fuel oil will - Answer Wax crystals
begin to form
Sulphur is a - Answer Corrosive chemical compound found in minor amounts in few oil
Name two reasons that water is found in a fuel oil storage tanks - Answer 1) water is heavier
than oil
2) it's a breeding ground for micro scopic bacterial growth
True or false) colour and odour or reliable indicators of the properties and qualities of fuel oil -
Answer False
The products of a complete combustion of fuel oil and air are - Answer Carbon dioxide
The ultimate CO2 from the combustion of number 2 fuel oil and air is - Answer 15.3%
Name three undesirable products incomplete incomplete combustion - Answer Soot, carbon
monoxide, reduced heat
, Carbon dioxide and nitrogen are - Answer Toxic gases
What gas is a inert and passes through the combustion reaction without significant effect except
for absorbing heat - Answer Nitrogen
Describe the symptoms of carbon monoxide poisoning - Answer Headaches, dizziness,
nausea without fever
(True or false) the appearance of a few oil flame specifically it's colour insert production, is the
best indicator of the quality of the combustion process - Answer False
Name the two ways of preparing feel oil for combustion - Answer Vaporization and
atomization
What effect with too small of combustion chamber have on combustion - Answer If the
combustion chamber is too small for firing right flame oil spray impingement and also
incomplete combustion
( True or false)hard fire brick is the best material for combustion chambers in residential
appliances - Answer False
The term combustion efficiency is properly used to refer to eficiency of the - Answer
Combustion reaction
Name the five ways in which heating heating appliance can lose the chemical heat energy of the
fuel - Answer 1. On cycle heat loss
2. Off cycle heat loss
3. Jacket heat loss
4. Distribution heat lost
5. Air infiltration heat loss
Explain on cycle heat loss - Answer Heat loss during an operation of the appliance
Explain our cycle heat loss - Answer Heat loss when an appliance is not operating
Explain jacket heat loss - Answer Heat loss by appliance appliance both on and off
Explain distribution heat loss - Answer Heat loss from ducks or piping
