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100+ Free MS Mechanical Practice Questions

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2026 Statistics

Key Facts: MS Mechanical Exam

70%

Passing Score

PSI MS Contractor Bulletin 4/23/2026

100 Q

Official Exam Questions

PSI MS Contractor Bulletin 4/23/2026

4 hours

Time Allowed

PSI MS Contractor Bulletin 4/23/2026

$120

PSI Exam Fee

PSI MS Contractor Bulletin 4/23/2026

Open book

Exam Format

PSI MS Contractor Bulletin 4/23/2026

MS Mechanical PSI trade exam: 100 questions, 70% pass, 4 hours, fee $120. Open-book MSBOC classification (bulletin 4/23/2026).

Sample MS Mechanical Practice Questions

Try these sample questions to test your MS Mechanical exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Per the International Mechanical Code, what protective control is required on steam and hot-water boilers to shut off the fuel supply if the water level falls below a safe point?
A.A high-limit aquastat only
B.A low-water cutoff
C.A flow switch on the expansion tank
D.A manual reset pressuretrol only
Explanation: IMC Section 1007 requires steam and hot-water boilers to be protected with a low-water cutoff control. The device interrupts the fuel supply before the heating surfaces are uncovered, which can cause overheating, cracking, or a steam explosion. A high-limit aquastat or pressure control is a separate temperature or pressure safety and does not substitute for water-level protection.
2A closed-loop hydronic heating circuit delivers 80,000 Btu/h with a design water temperature drop of 20°F. Using GPM = Btu/h ÷ (500 × ΔT), what is the required flow?
A.4 gpm
B.6 gpm
C.8 gpm
D.16 gpm
Explanation: Water weighs about 8.33 lb/gal. Multiplying by 60 minutes and the specific heat of water (1 Btu/lb-°F) gives the familiar 500 factor. Required flow is 80,000 ÷ (500 × 20) = 80,000 ÷ 10,000 = 8 gpm. A 20°F drop is the common residential hydronic design; a 10°F drop would double the flow.
3In a closed hydronic heating system, where should the circulator be arranged relative to the expansion tank for stable fill pressure?
A.Pump toward the expansion tank so the tank absorbs pump head
B.Pump away from the expansion tank, which is the point of no pressure change
C.Install the expansion tank on the suction of a booster only, never on the boiler loop
D.Omit the expansion tank if the relief valve is set at 30 psi
Explanation: The connection to the expansion tank is the point of no pressure change. Locating the circulator so it pumps away from that point adds the pump head to the system and keeps the boiler and piping above atmospheric pressure. Pumping toward the tank subtracts pump head from the system and can flash or cavitate at the pump suction.
4What is the typical pressure-relief-valve setting on a residential ASME hot-water heating boiler?
A.15 psi
B.30 psi
C.50 psi
D.150 psi
Explanation: Most residential hot-water heating boilers are ASME Section IV vessels with a 30 psi maximum allowable working pressure, so the relief valve is set at 30 psi. Steam heating boilers commonly relieve at 15 psi. A 150 psi valve is the typical setting on a domestic potable-water heater, not a hydronic heating boiler.
5Where is an air separator most effective on a hot-water boiler loop?
A.On the coldest return, just before the circulator suction
B.On the boiler supply outlet, where the water is hottest and air is least soluble
C.On the compression tank drain only
D.On a dead-end high point with no flow through the separator
Explanation: Air comes out of solution most readily where water is hottest and pressure is lowest. Placing a flow-through air separator on the boiler supply, near the expansion-tank connection, scoops that released air before it travels into the radiation. A separator on a stagnant high point or only on a tank drain will not continuously scrub circulating water.
6Makeup water that automatically feeds a closed hydronic heating boiler must be protected against which hazard?
A.Backflow of chemically treated boiler water into the potable supply
B.Excessive condensate acidity in the vent
C.Oil logging of the compression tank
D.Short-cycling of the low-water cutoff only
Explanation: Boiler water is a nonpotable, often chemically treated fluid. IPC backflow rules and IMC hydronic makeup practice require an approved backflow preventer (typically a reduced-pressure principle assembly or a listed dual-check with intermediate vent, as required by the hazard) on the makeup line. Without it, a pressure reversal can push boiler water into the building potable system.
7Per the International Fuel Gas Code, an individual appliance shutoff valve shall be located in the same room as the appliance and not more than how far from the appliance?
A.3 feet
B.6 feet
C.12 feet
D.25 feet
Explanation: IFGC 409.5 requires each appliance to have a shutoff valve separate from the appliance, in the same room, not more than 6 feet from the appliance, and upstream of the union or connector. The 6-foot limit keeps the valve accessible for service and emergency isolation. A manifold shutoff is a separate allowance and is not the default individual-valve rule.
8Where a gas appliance does not have a factory sediment trap, how shall the field sediment trap be built and located per the IFGC?
A.A tee with a capped nipple in the bottom opening, installed downstream of the appliance shutoff and as close to the inlet as practical
B.A 90-degree elbow drip at the meter only
C.A union installed upstream of the shutoff valve
D.A plugged tee in the vent connector
Explanation: IFGC 408.4 requires a sediment trap downstream of the equipment shutoff and as close to the appliance inlet as practical. The approved construction is a tee with a capped nipple in the bottom of the run, or another listed sediment device. Dirt and scale drop into the nipple instead of entering the gas valve. Illuminating appliances, ranges, clothes dryers, decorative appliances, and outdoor grills are excepted.
9When pressure-testing a new low-pressure fuel-gas piping system under the IFGC, what is the minimum test pressure?
A.The appliance working pressure of about 7 inches water column
B.1.5 times the proposed maximum working pressure, but not less than 3 psig
C.10 psig for every system, regardless of volume
D.50 psig, the same as a potable-water test
Explanation: IFGC 406.4.1 requires a test pressure of not less than 1-1/2 times the proposed maximum working pressure and not less than 3 psig. Typical natural-gas utilization pressure is only inches of water column, so the 3 psig floor governs. For a single-family dwelling or a system under 10 cubic feet, IFGC 406.4.2 allows a 10-minute duration; larger systems use a volume-based duration.
10Using the IFGC longest-length method and this excerpt of Table 402.4(2) (Schedule 40 metallic pipe, natural gas, inlet less than 2 psi, 0.5 inch w.c. drop) at 40 feet — 1/2 inch = 81 cfh, 3/4 inch = 170 cfh, 1 inch = 320 cfh — what is the smallest pipe that can supply a 100,000 Btu/h furnace (100 cfh at 1,000 Btu/cu ft) that is 40 feet of developed length from the meter?
A.3/8 inch
B.1/2 inch
C.3/4 inch
D.1 inch
Explanation: Convert input to cubic feet per hour: 100,000 Btu/h ÷ 1,000 Btu/cu ft = 100 cfh. The longest-length method sizes every section from the row for the longest run, here 40 feet. At 40 feet a 1/2-inch pipe carries only 81 cfh, which is less than 100 cfh. A 3/4-inch pipe carries 170 cfh and is the smallest size that meets the load.

About the MS Mechanical Exam

Mississippi Mechanical Contractor Examination is a classification trade examination administered by PSI for the Mississippi State Board of Contractors. The official open-book exam has 100 questions, a 70% passing standard, and 4 hours allowed. PSI examination fee is $120 per portion (bulletin updated 4/23/2026). This English-language MCQ bank is a study aid for the official content outline; it is not an official PSI form, does not replace the required Law and Business Management exam, and is not a substitute for MSBOC application review or the official open-book examination.

Questions

100 scored questions

Time Limit

4 hours

Passing Score

70%

Exam Fee

$120 (PSI Services LLC (for Mississippi State Board of Contractors))

MS Mechanical Exam Content Outline

6%

Boilers and Hydronics

Boilers and hydronic systems

10%

Gas Systems

Fuel gas systems

3%

Cleanouts

Plumbing cleanouts

5%

Plumbing Fixtures and Equipment

Fixtures and equipment

2%

Water Heaters

Water heaters

5%

Piping, valves, controls

Piping, valves, and controls

6%

Sheet Metal and Ducts

Sheet metal and ducts

5%

Water Supply

Water supply systems

4%

Hangers and Supports

Hangers and supports

5%

Drain, Waste, and Vent

DWV systems

2%

Backflow

Backflow prevention

4%

Traps and Interceptors

Traps and interceptors

3%

Developed length

Developed length calculations

8%

Isometric Analysis

Isometric plan reading

4%

Safety

Mechanical safety

3%

Joints and Connections

Pipe joints and connections

3%

General Plumbing Regulations

Plumbing code administration

4%

Fire Sprinklers

Fire sprinkler basics in mechanical work

4%

Refrigerants and Refrigeration

Refrigeration

4%

Heating and Cooling Principles

HVAC principles

5%

Load Calculations

Load calculations

1%

Testing, Adjusting and Balancing

TAB

4%

HVAC Equipment

HVAC equipment

How to Pass the MS Mechanical Exam

What You Need to Know

  • Passing score: 70%
  • Exam length: 100 questions
  • Time limit: 4 hours
  • Exam fee: $120

Keys to Passing

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

MS Mechanical Study Tips from Top Performers

1Study only the approved references listed for this classification in the current PSI Mississippi Contractor bulletin (updated 4/23/2026)
2Practice open-book navigation with permanent tabs and indexes before test day
3Drill OSHA 29 CFR 1926 topics that appear across nearly every trade outline
4Confirm MSBOC classification scope and eligibility at msboc.us before scheduling with PSI
5All applicants must also pass Law and Business Management unless it is waived

Frequently Asked Questions

How many questions are on the MS Mechanical exam?

The official PSI examination has 100 scored questions (plus possible unscored experimental items). Passing is 70% within 4 hours.

How much does the MS Mechanical exam cost?

PSI lists $120 per examination portion (Candidate Information Bulletin updated 4/23/2026). MSBOC application fees are separate: $400 commercial or $50 residential. Additional classifications are $100 each.

Is the Mississippi contractor exam open book?

Yes. PSI administers MSBOC classification exams as open book. Only bulletin-listed approved references are allowed; temporary tabs such as Post-it notes are prohibited.

Do I still need the Law and Business Management exam?

Yes. MSBOC requires the Mississippi Law and Business Management exam (50 questions, 70%, 2 hours) of all applicants. Reciprocity may waive a trade exam in some cases but does not waive Law and Business.