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COSC 325 HOUSTON (MECHANICAL) EXAM
QUESTIONS AND ANSWERS 2025
Mechanical division - .....ANSWER... ✔✔ 23
DX - - .....ANSWER... ✔✔ direct expansion
In a DX system, ___ moves back and forth between the
Condensor Unit and Air Handling Unit - .....ANSWER...
✔✔ refrigerant
Energy is measured in ___. - .....ANSWER... ✔✔ Btu
1 watt = - .....ANSWER... ✔✔ 3,412 Btu/h
1 ton = - .....ANSWER... ✔✔ 12,000 Btu/h
1 ton cools about ___ SF. - .....ANSWER... ✔✔ 350
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CFM - - .....ANSWER... ✔✔ Cubic Feet per Minute
FPM - - .....ANSWER... ✔✔ Feet Per Minute
SMACNA - - .....ANSWER... ✔✔ Sheet Metal and Air
Conditioning Contractors National Association
For duct construction, refer to ____ and ____. -
.....ANSWER... ✔✔ - International Mechanical Code
- SMACNA
Sheet metal ducts need to be ___. - .....ANSWER...
✔✔ insulated
Ductboard is made out of ___. - .....ANSWER... ✔✔
fiberglass
Ductboard is used in ___. - .....ANSWER... ✔✔
residential
Flex duct should only be used in ___. - .....ANSWER...
✔✔ short sections
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Trunk duct = - .....ANSWER... ✔✔ Main duct
Tap - - .....ANSWER... ✔✔ exit made out of trunk
Branch - - .....ANSWER... ✔✔ duct that extends from
the tap
Reduction - - .....ANSWER... ✔✔ lessens the size of the
ductwork
___ goes from larger to smaller. - .....ANSWER... ✔✔
Supply ductwork
Square duct is cheaper because of ___. - .....ANSWER...
✔✔ minimal surface area
250 Btu/h per ___ - .....ANSWER... ✔✔ person
Larger number in sheet metal = - .....ANSWER... ✔✔
thinner
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AHU - - .....ANSWER... ✔✔ Air Handling Unit
If there is no air blowing the ___ in your AHU. -
.....ANSWER... ✔✔ fan might be out
If water is dripping, your AHU is ___. - .....ANSWER...
✔✔ working
If your air is not getting cold, something is wrong with
the ____. - .....ANSWER... ✔✔ refrigerant
CU - - .....ANSWER... ✔✔ Condensing Unit
The CU ___ back and forth to the AHU. - .....ANSWER...
✔✔ pumps refrigerant
A ___ is larger and should be insulated. - .....ANSWER...
✔✔ suction line
A ___ is small and warm. - .....ANSWER... ✔✔ liquid
line
COSC 325 HOUSTON (MECHANICAL) EXAM
QUESTIONS AND ANSWERS 2025
Mechanical division - .....ANSWER... ✔✔ 23
DX - - .....ANSWER... ✔✔ direct expansion
In a DX system, ___ moves back and forth between the
Condensor Unit and Air Handling Unit - .....ANSWER...
✔✔ refrigerant
Energy is measured in ___. - .....ANSWER... ✔✔ Btu
1 watt = - .....ANSWER... ✔✔ 3,412 Btu/h
1 ton = - .....ANSWER... ✔✔ 12,000 Btu/h
1 ton cools about ___ SF. - .....ANSWER... ✔✔ 350
,2|Page
CFM - - .....ANSWER... ✔✔ Cubic Feet per Minute
FPM - - .....ANSWER... ✔✔ Feet Per Minute
SMACNA - - .....ANSWER... ✔✔ Sheet Metal and Air
Conditioning Contractors National Association
For duct construction, refer to ____ and ____. -
.....ANSWER... ✔✔ - International Mechanical Code
- SMACNA
Sheet metal ducts need to be ___. - .....ANSWER...
✔✔ insulated
Ductboard is made out of ___. - .....ANSWER... ✔✔
fiberglass
Ductboard is used in ___. - .....ANSWER... ✔✔
residential
Flex duct should only be used in ___. - .....ANSWER...
✔✔ short sections
,3|Page
Trunk duct = - .....ANSWER... ✔✔ Main duct
Tap - - .....ANSWER... ✔✔ exit made out of trunk
Branch - - .....ANSWER... ✔✔ duct that extends from
the tap
Reduction - - .....ANSWER... ✔✔ lessens the size of the
ductwork
___ goes from larger to smaller. - .....ANSWER... ✔✔
Supply ductwork
Square duct is cheaper because of ___. - .....ANSWER...
✔✔ minimal surface area
250 Btu/h per ___ - .....ANSWER... ✔✔ person
Larger number in sheet metal = - .....ANSWER... ✔✔
thinner
, 4|Page
AHU - - .....ANSWER... ✔✔ Air Handling Unit
If there is no air blowing the ___ in your AHU. -
.....ANSWER... ✔✔ fan might be out
If water is dripping, your AHU is ___. - .....ANSWER...
✔✔ working
If your air is not getting cold, something is wrong with
the ____. - .....ANSWER... ✔✔ refrigerant
CU - - .....ANSWER... ✔✔ Condensing Unit
The CU ___ back and forth to the AHU. - .....ANSWER...
✔✔ pumps refrigerant
A ___ is larger and should be insulated. - .....ANSWER...
✔✔ suction line
A ___ is small and warm. - .....ANSWER... ✔✔ liquid
line
