NC H3-1 Section 17 Practice Questions (Residential/Light
Commercial) | Most Tested Questions & 100% Correct
Answers | 2026 Update
1. To find the static pressure loss for a duct section, the total equivalent length
of the duct section is divided by and multiplied by the design static pressure
drop that was used to size the duct.
100
1000
50
10
2. If a restaurant decides to install two 10-foot long medium-duty kitchen hoods,
what would be the total required CFM of exhaust air for both hoods?
3000 cfm
10000 cfm
5000 cfm
2000 cfm
3. What is the maximum CFM for a 24" round spiral duct according to the ACCA
manual-Q?
4600 cfm
5800 cfm
3800 cfm
6000 cfm
4. When a sediment trap is used on a gas piping it must be installed ?
, Downstream of equipment shut off valve as possible
By the equipment manufacture
Upstream of equipment shut off valve as possible
Sediment traps are not required
5. Describe the process used to determine the equivalent round duct size from
the given rectangular duct dimensions.
The equivalent round duct size is based solely on the height of the
rectangular duct.
The equivalent round duct size is simply the average of the two
dimensions.
The equivalent round duct size is determined by the volume of air it
can carry.
The equivalent round duct size is calculated using the dimensions of
the rectangular duct and accounting for insulation.
6. Which code specifies the installation requirements for smoke detectors?
2018 NC fire code
2018 NC mechanical code
NFPA 72
NFPA 70
7. If the insulation quality of the building in Asheville is improved, how would
that likely affect the heat loss calculation?
The heat loss would fluctuate unpredictably.
The heat loss would remain the same.
, The heat loss would increase.
The heat loss would decrease.
8. What is the design friction rate for an air handling unit at an external static
pressure of .3 IWC and a total equivalent length of 480 feet?
0.06
0.08
0.10
0.04
9. What is the required amount of combustion air for a 60,000 btu/hr furnace
when using indoor air?
7000 cubic feet of air
8000 cubic feet of air
4950 cubic feet of air
5250 cubic feet of air
10. Where should dampers be installed in a residential duct system for proper
balancing?
At the trunk entrance fitting
At the return air stack head
At the box collar
Never install dampers in return ducts
11. If the pressure drop across a wet residential unitary evaporator coil increases
to 0.60 IWC while maintaining the same air flow, what might this indicate
about the coil's condition?
, The refrigerant levels in the system are too high.
The coil is functioning optimally and requires no maintenance.
The coil may be dirty or clogged, affecting airflow and efficiency.
The air flow has increased significantly beyond 1750 cfm.
12. If a duct heater is installed 5 feet away from the air handling unit, what
potential issues could arise?
Easier maintenance access
Improved air circulation
No issues will arise
Inefficient heating and increased heat loss
13. You are installing a medium-duty kitchen hood in a commercial application.
The hood type is a single island canopy hood. The hood is 10-feet long so
how many cfm of total exhaust air will be required?
2500 cfm
2000 cfm
3000 cfm
5000 cfm
14. If an HVAC system has a cooling load of 40,000 BTU/hr and the blower
produces 1200 CFM, what would be the cooling factor?
0.035
0.030
0.033
0.0333
Commercial) | Most Tested Questions & 100% Correct
Answers | 2026 Update
1. To find the static pressure loss for a duct section, the total equivalent length
of the duct section is divided by and multiplied by the design static pressure
drop that was used to size the duct.
100
1000
50
10
2. If a restaurant decides to install two 10-foot long medium-duty kitchen hoods,
what would be the total required CFM of exhaust air for both hoods?
3000 cfm
10000 cfm
5000 cfm
2000 cfm
3. What is the maximum CFM for a 24" round spiral duct according to the ACCA
manual-Q?
4600 cfm
5800 cfm
3800 cfm
6000 cfm
4. When a sediment trap is used on a gas piping it must be installed ?
, Downstream of equipment shut off valve as possible
By the equipment manufacture
Upstream of equipment shut off valve as possible
Sediment traps are not required
5. Describe the process used to determine the equivalent round duct size from
the given rectangular duct dimensions.
The equivalent round duct size is based solely on the height of the
rectangular duct.
The equivalent round duct size is simply the average of the two
dimensions.
The equivalent round duct size is determined by the volume of air it
can carry.
The equivalent round duct size is calculated using the dimensions of
the rectangular duct and accounting for insulation.
6. Which code specifies the installation requirements for smoke detectors?
2018 NC fire code
2018 NC mechanical code
NFPA 72
NFPA 70
7. If the insulation quality of the building in Asheville is improved, how would
that likely affect the heat loss calculation?
The heat loss would fluctuate unpredictably.
The heat loss would remain the same.
, The heat loss would increase.
The heat loss would decrease.
8. What is the design friction rate for an air handling unit at an external static
pressure of .3 IWC and a total equivalent length of 480 feet?
0.06
0.08
0.10
0.04
9. What is the required amount of combustion air for a 60,000 btu/hr furnace
when using indoor air?
7000 cubic feet of air
8000 cubic feet of air
4950 cubic feet of air
5250 cubic feet of air
10. Where should dampers be installed in a residential duct system for proper
balancing?
At the trunk entrance fitting
At the return air stack head
At the box collar
Never install dampers in return ducts
11. If the pressure drop across a wet residential unitary evaporator coil increases
to 0.60 IWC while maintaining the same air flow, what might this indicate
about the coil's condition?
, The refrigerant levels in the system are too high.
The coil is functioning optimally and requires no maintenance.
The coil may be dirty or clogged, affecting airflow and efficiency.
The air flow has increased significantly beyond 1750 cfm.
12. If a duct heater is installed 5 feet away from the air handling unit, what
potential issues could arise?
Easier maintenance access
Improved air circulation
No issues will arise
Inefficient heating and increased heat loss
13. You are installing a medium-duty kitchen hood in a commercial application.
The hood type is a single island canopy hood. The hood is 10-feet long so
how many cfm of total exhaust air will be required?
2500 cfm
2000 cfm
3000 cfm
5000 cfm
14. If an HVAC system has a cooling load of 40,000 BTU/hr and the blower
produces 1200 CFM, what would be the cooling factor?
0.035
0.030
0.033
0.0333
