Michigan (MI) Hydronic Heating, Cooling & Process
Piping Exam Prep: 150 Newest Questions with
Answers, 2021 MMC/MRC Study Guide & ASME B31.3
Review | pdf
Master the Michigan Mechanical Contractor Classification 3 Exam with this comprehensive 150-
question practice test. This guide is specifically engineered for Michigan contractors focusing on Hydronic
Heating and Cooling and Industrial Process Piping.
Our coverage includes deep dives into the 2021 Michigan Mechanical Code (MMC), 2015/2021 Michigan
Residential Code (MRC), and ASME B31.3 standards. Key topics covered include boiler safety
controls, low-water cutoffs, expansion tank sizing, combustion air calculations, and hydrostatic
leak testing procedures. Whether you are working with residential PEX radiant floors or high-pressure
industrial steel piping, these practice questions provide the technical explanations and code references
needed to pass the LARA/PSI state exam on your first attempt.
1. According to the Michigan Mechanical Code, what is the minimum duration for
a hydrostatic test on hydronic piping?
A. 10 minutes
B. 15 minutes
C. 30 minutes
D. 60 minutes
Explanation: MMC Section 1208.1 requires hydronic piping to be tested for at
least 15 minutes to ensure no leaks are present under pressure.
2. What is the required hydrostatic test pressure for a hydronic system?
A. 50 psi
B. 100 psi
C. 1.5 times the maximum system design pressure, but not less than 100 psi
D. 3 times the design pressure
Explanation: The code specifies 1.5 times the design pressure to ensure
safety, with a 100 psi floor for low-pressure systems.
,3. In a hydronic system, where should the expansion tank be connected to the
system?
A. At the discharge of the pump
B. On the suction side of the pump (Point of No Pressure Change)
C. At the highest radiator
D. Directly to the boiler drain valve
Explanation: Connecting the expansion tank to the suction side prevents the
pump’s head pressure from being added to the system’s static pressure, avoiding relief
valve "weeping."
4. What is the purpose of an "Air Scoop" or "Air Separator" in a hydronic loop?
A. To remove entrained air bubbles from the circulating fluid
B. To add oxygen to the water
C. To increase the water pressure
D. To act as a secondary heat exchanger
Explanation: Air in the system causes noise, corrosion, and "air locks" that
stop flow; separators remove this air as the water circulates.
5. Which pipe material is PROHIBITED for use in a hydronic piping system by the
Michigan Mechanical Code?
A. Copper tubing
B. PEX
C. Lead pipe
D. Steel pipe
Explanation: Lead is restricted due to health and safety standards; MMC Table
1202.4 lists approved materials like Copper, PEX, CPVC, and Steel.
6. For process piping under ASME B31.3, what is "Category D" fluid service?
A. High-pressure steam
B. Non-flammable, non-toxic fluids at low pressure and temperature
C. Lethal substances
D. Flammable gases
Explanation: Category D service is for fluids that are non-hazardous, below
150 psi, and between -20°F and 366°F.
7. When installing a low-water fuel cutoff on a hot water boiler, where must it be
located?
A. Below the burner
,B. Above the lowest safe permissible water level
C. In the expansion tank
D. On the return line
Explanation: The cutoff ensures the burner shuts down if water drops too low,
preventing "dry firing" and potential boiler explosion.
8. What is the maximum interval for supports on 1-inch horizontal copper tubing
in a hydronic system?
A. 4 feet
B. 5 feet
C. 6 feet
D. 10 feet
Explanation: Per MMC Table 305.4, 1-inch and smaller copper tubing requires
supports every 6 feet to prevent sagging.
9. A "closed" hydronic system requires which of the following to protect against
thermal expansion?
A. A check valve
B. An expansion tank
C. A gate valve
D. A cooling tower
Explanation: Because water is non-compressible, heating it in a closed loop
creates pressure that must be absorbed by an expansion tank.
10. What is the standard "Delta T" (Temperature Drop) used for sizing most
residential hydronic baseboard systems?
A. 5°F
B. 10°F
C. 20°F
D. 50°F
Explanation: A 20°F temperature difference between the supply and return is
the industry standard for calculating flow rate (GPM).
11. Which valve is used to prevent the backflow of boiler water into the potable
water supply?
A. Butterfly valve
B. Backflow preventer with intermediate atmospheric vent
, C. Gate valve
D. Globe valve
Explanation: Chemicals and stagnant water in a boiler must be isolated from
drinking water using a high-grade backflow preventer.
12. In hydronic radiant floor heating, what is the maximum recommended water
temperature for the tubing?
A. 100°F
B. 140°F (often lower depending on floor finish)
C. 180°F
D. 210°F
Explanation: High temperatures can damage wood floors and cause
discomfort; mixing valves are used to keep radiant loops cooler than baseboard loops.
13. What type of pump is most commonly used as a "Circulator" in hydronic
systems?
A. Positive displacement pump
B. Centrifugal pump
C. Piston pump
D. Gear pump
Explanation: Centrifugal pumps are ideal for moving high volumes of fluid at
the relatively low pressures found in closed-loop heating.
14. Per ASME B31.3, what is a "Normal" fluid service?
A. Only domestic water
B. Fluid service not subject to Category D, M, or High-Pressure criteria
C. Air only
D. Vacuum service
Explanation: Most industrial process piping falls under "Normal" fluid service
unless specifically categorized otherwise.
15. What is the minimum size of a discharge pipe for a pressure relief valve?
A. Not less than the size of the valve outlet
B. 1/2 inch
C. 2 inches
D. One size larger than the valve outlet
Explanation: Discharge piping must not be restricted; it must match or exceed
the outlet diameter of the relief valve.
Piping Exam Prep: 150 Newest Questions with
Answers, 2021 MMC/MRC Study Guide & ASME B31.3
Review | pdf
Master the Michigan Mechanical Contractor Classification 3 Exam with this comprehensive 150-
question practice test. This guide is specifically engineered for Michigan contractors focusing on Hydronic
Heating and Cooling and Industrial Process Piping.
Our coverage includes deep dives into the 2021 Michigan Mechanical Code (MMC), 2015/2021 Michigan
Residential Code (MRC), and ASME B31.3 standards. Key topics covered include boiler safety
controls, low-water cutoffs, expansion tank sizing, combustion air calculations, and hydrostatic
leak testing procedures. Whether you are working with residential PEX radiant floors or high-pressure
industrial steel piping, these practice questions provide the technical explanations and code references
needed to pass the LARA/PSI state exam on your first attempt.
1. According to the Michigan Mechanical Code, what is the minimum duration for
a hydrostatic test on hydronic piping?
A. 10 minutes
B. 15 minutes
C. 30 minutes
D. 60 minutes
Explanation: MMC Section 1208.1 requires hydronic piping to be tested for at
least 15 minutes to ensure no leaks are present under pressure.
2. What is the required hydrostatic test pressure for a hydronic system?
A. 50 psi
B. 100 psi
C. 1.5 times the maximum system design pressure, but not less than 100 psi
D. 3 times the design pressure
Explanation: The code specifies 1.5 times the design pressure to ensure
safety, with a 100 psi floor for low-pressure systems.
,3. In a hydronic system, where should the expansion tank be connected to the
system?
A. At the discharge of the pump
B. On the suction side of the pump (Point of No Pressure Change)
C. At the highest radiator
D. Directly to the boiler drain valve
Explanation: Connecting the expansion tank to the suction side prevents the
pump’s head pressure from being added to the system’s static pressure, avoiding relief
valve "weeping."
4. What is the purpose of an "Air Scoop" or "Air Separator" in a hydronic loop?
A. To remove entrained air bubbles from the circulating fluid
B. To add oxygen to the water
C. To increase the water pressure
D. To act as a secondary heat exchanger
Explanation: Air in the system causes noise, corrosion, and "air locks" that
stop flow; separators remove this air as the water circulates.
5. Which pipe material is PROHIBITED for use in a hydronic piping system by the
Michigan Mechanical Code?
A. Copper tubing
B. PEX
C. Lead pipe
D. Steel pipe
Explanation: Lead is restricted due to health and safety standards; MMC Table
1202.4 lists approved materials like Copper, PEX, CPVC, and Steel.
6. For process piping under ASME B31.3, what is "Category D" fluid service?
A. High-pressure steam
B. Non-flammable, non-toxic fluids at low pressure and temperature
C. Lethal substances
D. Flammable gases
Explanation: Category D service is for fluids that are non-hazardous, below
150 psi, and between -20°F and 366°F.
7. When installing a low-water fuel cutoff on a hot water boiler, where must it be
located?
A. Below the burner
,B. Above the lowest safe permissible water level
C. In the expansion tank
D. On the return line
Explanation: The cutoff ensures the burner shuts down if water drops too low,
preventing "dry firing" and potential boiler explosion.
8. What is the maximum interval for supports on 1-inch horizontal copper tubing
in a hydronic system?
A. 4 feet
B. 5 feet
C. 6 feet
D. 10 feet
Explanation: Per MMC Table 305.4, 1-inch and smaller copper tubing requires
supports every 6 feet to prevent sagging.
9. A "closed" hydronic system requires which of the following to protect against
thermal expansion?
A. A check valve
B. An expansion tank
C. A gate valve
D. A cooling tower
Explanation: Because water is non-compressible, heating it in a closed loop
creates pressure that must be absorbed by an expansion tank.
10. What is the standard "Delta T" (Temperature Drop) used for sizing most
residential hydronic baseboard systems?
A. 5°F
B. 10°F
C. 20°F
D. 50°F
Explanation: A 20°F temperature difference between the supply and return is
the industry standard for calculating flow rate (GPM).
11. Which valve is used to prevent the backflow of boiler water into the potable
water supply?
A. Butterfly valve
B. Backflow preventer with intermediate atmospheric vent
, C. Gate valve
D. Globe valve
Explanation: Chemicals and stagnant water in a boiler must be isolated from
drinking water using a high-grade backflow preventer.
12. In hydronic radiant floor heating, what is the maximum recommended water
temperature for the tubing?
A. 100°F
B. 140°F (often lower depending on floor finish)
C. 180°F
D. 210°F
Explanation: High temperatures can damage wood floors and cause
discomfort; mixing valves are used to keep radiant loops cooler than baseboard loops.
13. What type of pump is most commonly used as a "Circulator" in hydronic
systems?
A. Positive displacement pump
B. Centrifugal pump
C. Piston pump
D. Gear pump
Explanation: Centrifugal pumps are ideal for moving high volumes of fluid at
the relatively low pressures found in closed-loop heating.
14. Per ASME B31.3, what is a "Normal" fluid service?
A. Only domestic water
B. Fluid service not subject to Category D, M, or High-Pressure criteria
C. Air only
D. Vacuum service
Explanation: Most industrial process piping falls under "Normal" fluid service
unless specifically categorized otherwise.
15. What is the minimum size of a discharge pipe for a pressure relief valve?
A. Not less than the size of the valve outlet
B. 1/2 inch
C. 2 inches
D. One size larger than the valve outlet
Explanation: Discharge piping must not be restricted; it must match or exceed
the outlet diameter of the relief valve.
