Absa 4b Final Exam, Practice Exam And Study Guide

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Absa 4b Final Exam, Practice Exam And Study Guide (All In One Document) Newest 2025 Complete Questions And Correct Detailed Answers (Verified Answers) |Already Graded A+

An item found upstream of an operating control switch is a

• modutrol motor
• siphon
• combustion air proving switch
• test connection for an inspector
• feedwater pressure gage - ANSWER-B

On a multiburner boiler the high fire nozzle will

• be in operation on start-up
• operate continuously when steam demand exceeds boiler

capacity

• be ignited by a pilot flame
• respond to electrical resistance
• operate regardless of where the manual over-ride switch 1 / 4

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is set - ANSWER-B

A manual "high-low" switch should be switched to "high" or "auto"

• as soon as the main flame has stabilized
• prior to ignition of the main flame
• when pressure is too low
• when the boiler has been properly warmed up
• during boiler pre-purge - ANSWER-D

A resistance control or "potentiometer" for modulating control

• works in conjunction with a modutrol motor
• utilizes a mercury switch
• senses steam temperature
• can only be used on a fully automatic boiler
• can operate only in the vertical position - ANSWER-A

A potentiometer control

• varies electrical current to a modutrol motor 2 / 4

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• will start and stop a boiler
• cannot have its settings adjusted
• eliminates the need for a high limit control
• will not result in simultaneous adjustment of air and

fuel - ANSWER-A

A high limit control switch

• is necessary on all boilers
• activates after the safety valve opens
• is a normally open switch
• usually does not require manual resetting
• must be used when a boiler is not under continuous

supervision - ANSWER-E

Prior to a boiler safety valve popping during routine boiler operation

• a try lever test should be performed
• the pressure gage should be checked
• the high limit switch should open
• the feedwater pump should stop 3 / 4

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• the high level alarm should sound - ANSWER-C

A hot water boiler operating control can be a pressure switch

• which is normally open
• which is sensitive to the expansion and contraction of

boiler water

• utilizing a closed liquid filled system
• sensitive to steam pressure
• sensitive to boiler water pressure - ANSWER-C

A thermal element is

• used to measure pressure
• capable of sensing temperature and converting it to a

pressure signal

• a type of open system
• used to measure heat content
• commonly termed an "aquastat" - ANSWER-B

An aquastat

• senses water level
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