DC 3rd Class Test Exam Newest 2026 Questions
and Correct Detailed Answers Already Graded A+
How often do you check the high limit switch? - CORRECT ANSWER-Annually
What is the recommended time for a complete external inspection of a boiler? -
CORRECT ANSWER-once per shift
What is the first thing to do when shutting down a boiler? - CORRECT
ANSWER-To turn off the fire
A flow control should be blown down when? - CORRECT ANSWER-once per
shift
How often should you check the Low Water Fuel Cut off? - CORRECT ANSWER-
once per shift
Why is oil added to the refrigerant? - CORRECT ANSWER-lubrication of the
compressor
Keep refrigerant migrating
,Recycled and filtered refrigerant can be used where? - CORRECT ANSWER-By
the same owner in the same type of equipment
Data printed on the equipment nameplate would include manufacturer, model,
and serial number and________________? - CORRECT ANSWER-Stamp of
approval from commissioning authority
How many BTU's does it take to raise 10 lbs of steam from 40 to 41 degrees? -
CORRECT ANSWER-1 BTU
When working on a boiler, permits should be required? - CORRECT ANSWER-
For every shift
How many things do safety controls protect against? - CORRECT ANSWER-
Over pressure
Over Heating
Fire side explosions
What chemical compounds in water cause permanent hardness? - CORRECT
ANSWER-Calcium Sulfate and Magnesium Silicate
,What chemicals are used to combat corrosion? - CORRECT ANSWER-sodium
sulfite and hydrazine
You have boiler water that is found to have a PH of 5. What compound do you
add to neutralize? - CORRECT ANSWER-bases
What produces soft scale? - CORRECT ANSWER-calcium carbonate and
magnesium carbonate
With normal oxygen and low alkalinity, what is added to boiler water? -
CORRECT ANSWER-Neutralizing Amines
What is hard forming scale? - CORRECT ANSWER-silica
Which chemicals are used to combat scale? - CORRECT ANSWER-Combined
Phosphate Treatment
Which compound is not heat produce? - CORRECT ANSWER-Nitrogen
, What takes no actual action in combustion? - CORRECT ANSWER-Nitrogen
With hydroxide present & normal oxygen levels; which chemical will cause
problems? - CORRECT ANSWER-Chlorine
The component in which liquid vapor by absorbing heat is called? - CORRECT
ANSWER-evaporator
the best answer for an electrical grounding method? - CORRECT ANSWER-
Metal stake drive 8 foot into the ground.
A _____ valve should be used for throttling purposes? - CORRECT ANSWER-
Globe
What is the acceptable range for residual sodium sulfite in the boiler maintain? -
CORRECT ANSWER-30-70
What is the BTU content of a gallon of #4 fuel oil? - CORRECT ANSWER-
146,000
and Correct Detailed Answers Already Graded A+
How often do you check the high limit switch? - CORRECT ANSWER-Annually
What is the recommended time for a complete external inspection of a boiler? -
CORRECT ANSWER-once per shift
What is the first thing to do when shutting down a boiler? - CORRECT
ANSWER-To turn off the fire
A flow control should be blown down when? - CORRECT ANSWER-once per
shift
How often should you check the Low Water Fuel Cut off? - CORRECT ANSWER-
once per shift
Why is oil added to the refrigerant? - CORRECT ANSWER-lubrication of the
compressor
Keep refrigerant migrating
,Recycled and filtered refrigerant can be used where? - CORRECT ANSWER-By
the same owner in the same type of equipment
Data printed on the equipment nameplate would include manufacturer, model,
and serial number and________________? - CORRECT ANSWER-Stamp of
approval from commissioning authority
How many BTU's does it take to raise 10 lbs of steam from 40 to 41 degrees? -
CORRECT ANSWER-1 BTU
When working on a boiler, permits should be required? - CORRECT ANSWER-
For every shift
How many things do safety controls protect against? - CORRECT ANSWER-
Over pressure
Over Heating
Fire side explosions
What chemical compounds in water cause permanent hardness? - CORRECT
ANSWER-Calcium Sulfate and Magnesium Silicate
,What chemicals are used to combat corrosion? - CORRECT ANSWER-sodium
sulfite and hydrazine
You have boiler water that is found to have a PH of 5. What compound do you
add to neutralize? - CORRECT ANSWER-bases
What produces soft scale? - CORRECT ANSWER-calcium carbonate and
magnesium carbonate
With normal oxygen and low alkalinity, what is added to boiler water? -
CORRECT ANSWER-Neutralizing Amines
What is hard forming scale? - CORRECT ANSWER-silica
Which chemicals are used to combat scale? - CORRECT ANSWER-Combined
Phosphate Treatment
Which compound is not heat produce? - CORRECT ANSWER-Nitrogen
, What takes no actual action in combustion? - CORRECT ANSWER-Nitrogen
With hydroxide present & normal oxygen levels; which chemical will cause
problems? - CORRECT ANSWER-Chlorine
The component in which liquid vapor by absorbing heat is called? - CORRECT
ANSWER-evaporator
the best answer for an electrical grounding method? - CORRECT ANSWER-
Metal stake drive 8 foot into the ground.
A _____ valve should be used for throttling purposes? - CORRECT ANSWER-
Globe
What is the acceptable range for residual sodium sulfite in the boiler maintain? -
CORRECT ANSWER-30-70
What is the BTU content of a gallon of #4 fuel oil? - CORRECT ANSWER-
146,000
