HVAC EXAM 1
Explain how carbon monoxide is formed. - Answer Carbon monoxide (CO) is a
byproduct of incomplete combustion
List agencies that perform testing to verify equipment performance. - Answer AHRI,
CSA International, and Underwriters Laboratories (UL)
What is the purpose of excess air in furnace combustion? - Answer Insufficient
combustion air can produce hazardous conditions, if too little oxygen is supplied, part of
the byproducts will be dangerous carbon monoxide gas rather than harmless carbon
dioxide gas. The lack of combustion air can also keep a natural draft vent from
operating, stopping the flue gases from rising up the flue.
Why are LP gases considered more hazardous than natural gas? - Answer LP gas is
heavier than air so it stays closer to the ground if it escapes and can cause an
explosion. Natural gas is lighter than air so it can rise and not cause any explosions
should it escape.
Describe the two types of flames and their characteristics. - Answer Yellow flame and
blue flame; yellow flames are characteristic of luminous combustion, a process that
produces a little heat, lots of light, and lots of carbon monoxide. Blue flames are
characteristic of nonluminous combustion, a process that produces little light, lots of
heat, and no carbon monoxide.
Explain the causes of the flue gas condensation and how it can be stopped. - Answer
When the fuel burning system cycles on and off to meet the demand, the flue passages
cool down during the off cycle. When the system starts up again, condensate forms
briefly on the surfaces until they are heated above the dew point temperature.
3 TYPES OF exchangers - Answer sectionalized and seprentine
What is the standard VA rating for most HVACR systems? - Answer 40 VA
A given transformer has a primary voltage of 240 V and a secondary voltage of 24 V.
Assuming the transformer is rated at 40 VA, what is the secondary current? - Answer
1.67 A
What is a typical high limit cut out temperature? - Answer As a safety limit, some have
fixed limits temperature settings; others are adjustable (approximately 180-200 degrees
F)
List the four areas of an electronic control board that should be identified when
troubleshooting. - Answer The input, output, board ground, and power supply
Explain how carbon monoxide is formed. - Answer Carbon monoxide (CO) is a
byproduct of incomplete combustion
List agencies that perform testing to verify equipment performance. - Answer AHRI,
CSA International, and Underwriters Laboratories (UL)
What is the purpose of excess air in furnace combustion? - Answer Insufficient
combustion air can produce hazardous conditions, if too little oxygen is supplied, part of
the byproducts will be dangerous carbon monoxide gas rather than harmless carbon
dioxide gas. The lack of combustion air can also keep a natural draft vent from
operating, stopping the flue gases from rising up the flue.
Why are LP gases considered more hazardous than natural gas? - Answer LP gas is
heavier than air so it stays closer to the ground if it escapes and can cause an
explosion. Natural gas is lighter than air so it can rise and not cause any explosions
should it escape.
Describe the two types of flames and their characteristics. - Answer Yellow flame and
blue flame; yellow flames are characteristic of luminous combustion, a process that
produces a little heat, lots of light, and lots of carbon monoxide. Blue flames are
characteristic of nonluminous combustion, a process that produces little light, lots of
heat, and no carbon monoxide.
Explain the causes of the flue gas condensation and how it can be stopped. - Answer
When the fuel burning system cycles on and off to meet the demand, the flue passages
cool down during the off cycle. When the system starts up again, condensate forms
briefly on the surfaces until they are heated above the dew point temperature.
3 TYPES OF exchangers - Answer sectionalized and seprentine
What is the standard VA rating for most HVACR systems? - Answer 40 VA
A given transformer has a primary voltage of 240 V and a secondary voltage of 24 V.
Assuming the transformer is rated at 40 VA, what is the secondary current? - Answer
1.67 A
What is a typical high limit cut out temperature? - Answer As a safety limit, some have
fixed limits temperature settings; others are adjustable (approximately 180-200 degrees
F)
List the four areas of an electronic control board that should be identified when
troubleshooting. - Answer The input, output, board ground, and power supply
