C20 EXAM 2025 WITH 100% ACCURATE
ANSWERS
1. Describe the recommended method for cutting capillary tubing and explain
why it is preferred over other methods.
The recommended method is to use a tubing cutter, cut part way
then break off by hand, as it ensures a clean cut without damaging
the tubing.
A saw is recommended for its precision in cutting.
Using pliers is preferred because it is quicker and easier.
A three-corner file is used to smooth the edges after cutting.
2. Describe how an imbalance of fuel and air can affect the combustion
process in a gas furnace.
An imbalance of fuel and air only affects the noise level of the
furnace.
An imbalance of fuel and air has no effect on combustion.
An imbalance of fuel and air can lead to incomplete combustion,
resulting in the production of black soot.
An imbalance of fuel and air increases efficiency and reduces
emissions.
3. Describe the role of a Type II kitchen hood in maintaining kitchen safety
and comfort.
A Type II kitchen hood is designed to cool the kitchen and reduce
energy costs.
,A Type II kitchen hood helps maintain safety and comfort by
removing steam, vapor, heat, and odors from the kitchen
, environment.
A Type II kitchen hood is primarily used for filtering grease and
smoke.
A Type II kitchen hood is used to ventilate gas appliances only.
4. If the manifold pressure of an LP gas furnace is incorrectly set to 9 inches of
water column, what potential issues could arise?
No impact on furnace performance.
Enhanced airflow and heating capacity.
Improved energy efficiency and reduced operational costs.
Inefficient combustion and increased risk of carbon monoxide
production.
5. What is the maximum allowed distance between support straps for flexible
duct?
2'
8'
4'
6'
6. If a technician finds that a gas furnace is producing black soot, what steps
should they take to diagnose and resolve the issue?
Check the fuel-to-air ratio and inspect the flue for blockages.
Increase the fuel supply and reduce air intake.
Replace the furnace immediately without inspection.
, Only clean the soot without checking for underlying causes.
7. If a new type of nonmetallic material is proposed for return-air ducts that is
non-toxic and can support 100 lb of dead weight but does not meet the fire
resistance requirement, what should be the course of action?
The material can be used if it is coated with a fire-resistant layer.
The material can be used as long as it is installed in a non-
combustible area.
The material can be used if it is tested for other safety measures.
The material should not be used for return-air ducts.
8. Why is a warm-air register placed under a window?
so it is out of the way
drafts are eliminated
it will heat the air faster
decoration
9. What is one requirement for nonmetallic return-air ducts?
can support 100 lb of dead weight
cannot burn
are made of non-toxic materials
have as much fire resistance as a 1" thick piece of wood
10. What is the maximum ladder length approved by Cal/OSHA?
30 ft
ANSWERS
1. Describe the recommended method for cutting capillary tubing and explain
why it is preferred over other methods.
The recommended method is to use a tubing cutter, cut part way
then break off by hand, as it ensures a clean cut without damaging
the tubing.
A saw is recommended for its precision in cutting.
Using pliers is preferred because it is quicker and easier.
A three-corner file is used to smooth the edges after cutting.
2. Describe how an imbalance of fuel and air can affect the combustion
process in a gas furnace.
An imbalance of fuel and air only affects the noise level of the
furnace.
An imbalance of fuel and air has no effect on combustion.
An imbalance of fuel and air can lead to incomplete combustion,
resulting in the production of black soot.
An imbalance of fuel and air increases efficiency and reduces
emissions.
3. Describe the role of a Type II kitchen hood in maintaining kitchen safety
and comfort.
A Type II kitchen hood is designed to cool the kitchen and reduce
energy costs.
,A Type II kitchen hood helps maintain safety and comfort by
removing steam, vapor, heat, and odors from the kitchen
, environment.
A Type II kitchen hood is primarily used for filtering grease and
smoke.
A Type II kitchen hood is used to ventilate gas appliances only.
4. If the manifold pressure of an LP gas furnace is incorrectly set to 9 inches of
water column, what potential issues could arise?
No impact on furnace performance.
Enhanced airflow and heating capacity.
Improved energy efficiency and reduced operational costs.
Inefficient combustion and increased risk of carbon monoxide
production.
5. What is the maximum allowed distance between support straps for flexible
duct?
2'
8'
4'
6'
6. If a technician finds that a gas furnace is producing black soot, what steps
should they take to diagnose and resolve the issue?
Check the fuel-to-air ratio and inspect the flue for blockages.
Increase the fuel supply and reduce air intake.
Replace the furnace immediately without inspection.
, Only clean the soot without checking for underlying causes.
7. If a new type of nonmetallic material is proposed for return-air ducts that is
non-toxic and can support 100 lb of dead weight but does not meet the fire
resistance requirement, what should be the course of action?
The material can be used if it is coated with a fire-resistant layer.
The material can be used as long as it is installed in a non-
combustible area.
The material can be used if it is tested for other safety measures.
The material should not be used for return-air ducts.
8. Why is a warm-air register placed under a window?
so it is out of the way
drafts are eliminated
it will heat the air faster
decoration
9. What is one requirement for nonmetallic return-air ducts?
can support 100 lb of dead weight
cannot burn
are made of non-toxic materials
have as much fire resistance as a 1" thick piece of wood
10. What is the maximum ladder length approved by Cal/OSHA?
30 ft
