1 | Page
CUSTODIAN TEST PREP
2026/2027 ACTUAL QUESTIONS
WITH VERIFIED ANSWERS.
What is the most important steam-boiler safety principle? -
ANSWER-Maintaining proper water level
What should an operator do if no water is visible in the gauge
glass of a steam boiler? - ANSWER-Shut the burner down and
determine true water level
What is the purpose of the low-water cutoff? - ANSWER-To
shut off fuel when water falls below a safe level
What can cause a float-type LWCO to fail? - ANSWER-Sludge
or scale in the chamber
What does the gauge glass show in a boiler? - ANSWER-Water
level
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What does blowing down the water column help confirm? -
ANSWER-That the level passages are open and accurate
How is the operating pressure controlled on a steam boiler? -
ANSWER-By the pressure control
What is the operating control for temperature on a hot-water
boiler? - ANSWER-Aquastat
What does the safety valve protect the boiler from? - ANSWER-
Overpressure
What should never be done to a safety valve in service? -
ANSWER-It should never be plugged or isolated
What can scale buildup in an LWCO chamber cause? -
ANSWER-False level sensing
,3 | Page
What is the purpose of bottom blowdown? - ANSWER-To
remove sediment from low points
What does the water column connect in a boiler? - ANSWER-
The boiler to the gauge glass and low-water controls
How is a pressure control used for normal cycling different? -
ANSWER-It is different from the safety high-limit device
What does frequent lifting of a safety valve usually indicate? -
ANSWER-Another problem such as control failure or overfiring
Why can a clogged gauge glass connection be dangerous? -
ANSWER-It may show a false normal water level
What is the purpose of the feedwater system? - ANSWER-To
maintain safe boiler water level
How does a steam boiler differ from a hot-water boiler? -
ANSWER-It produces steam for distribution
, 4 | Page
What should NOT be done if a nuisance trip occurs on an
LWCO? - ANSWER-The control should NOT be bypassed as a
normal response
What can poor heat transfer in a boiler result from? - ANSWER-
Scale and sediment buildup
What is the function of a fuse in a circuit? - ANSWER-To melt
open during overcurrent
What is the best action if a breaker keeps tripping? - ANSWER-
Find and correct the cause
What does grounding mainly help with? - ANSWER-Stabilizing
the system and reducing shock hazards
What is bonding in electrical systems? - ANSWER-Connecting
metal parts together so that fault current can clear safely
CUSTODIAN TEST PREP
2026/2027 ACTUAL QUESTIONS
WITH VERIFIED ANSWERS.
What is the most important steam-boiler safety principle? -
ANSWER-Maintaining proper water level
What should an operator do if no water is visible in the gauge
glass of a steam boiler? - ANSWER-Shut the burner down and
determine true water level
What is the purpose of the low-water cutoff? - ANSWER-To
shut off fuel when water falls below a safe level
What can cause a float-type LWCO to fail? - ANSWER-Sludge
or scale in the chamber
What does the gauge glass show in a boiler? - ANSWER-Water
level
,2 | Page
What does blowing down the water column help confirm? -
ANSWER-That the level passages are open and accurate
How is the operating pressure controlled on a steam boiler? -
ANSWER-By the pressure control
What is the operating control for temperature on a hot-water
boiler? - ANSWER-Aquastat
What does the safety valve protect the boiler from? - ANSWER-
Overpressure
What should never be done to a safety valve in service? -
ANSWER-It should never be plugged or isolated
What can scale buildup in an LWCO chamber cause? -
ANSWER-False level sensing
,3 | Page
What is the purpose of bottom blowdown? - ANSWER-To
remove sediment from low points
What does the water column connect in a boiler? - ANSWER-
The boiler to the gauge glass and low-water controls
How is a pressure control used for normal cycling different? -
ANSWER-It is different from the safety high-limit device
What does frequent lifting of a safety valve usually indicate? -
ANSWER-Another problem such as control failure or overfiring
Why can a clogged gauge glass connection be dangerous? -
ANSWER-It may show a false normal water level
What is the purpose of the feedwater system? - ANSWER-To
maintain safe boiler water level
How does a steam boiler differ from a hot-water boiler? -
ANSWER-It produces steam for distribution
, 4 | Page
What should NOT be done if a nuisance trip occurs on an
LWCO? - ANSWER-The control should NOT be bypassed as a
normal response
What can poor heat transfer in a boiler result from? - ANSWER-
Scale and sediment buildup
What is the function of a fuse in a circuit? - ANSWER-To melt
open during overcurrent
What is the best action if a breaker keeps tripping? - ANSWER-
Find and correct the cause
What does grounding mainly help with? - ANSWER-Stabilizing
the system and reducing shock hazards
What is bonding in electrical systems? - ANSWER-Connecting
metal parts together so that fault current can clear safely
