Ohio Hydronics Contractor Exam Practice
Questions and Correct Answers (Verified Answers)
Plus Rationale 2026/2027 Q&A | Instant Download
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1. A hydronic heating system requires 60,000 BTU/hr. What flow rate is needed with a
20°F temperature drop?
A. 3 GPM
B. 6 GPM
C. 9 GPM
D. 12 GPM
Answer: B. 6 GPM
Rationale: GPM = BTU ÷ (500 × ΔT) = 60,000 ÷ (500 × 20) = 6 GPM.
2. What is the purpose of an expansion tank in hydronic systems?
A. Increase pressure
B. Absorb thermal expansion
C. Reduce airflow
D. Store heat
Answer: B. Absorb thermal expansion
Rationale: Expansion tanks accommodate volume changes as water heats and expands.
3. What is the function of a circulator pump?
A. Heat water
B. Move water through system
C. Increase pressure only
D. Store water
Answer: B. Move water through system
Rationale: Circulators ensure continuous flow in hydronic loops.
4. What is the typical temperature drop (ΔT) for hydronic heating systems?
A. 5°F
B. 10°F
,C. 20°F
D. 40°F
Answer: C. 20°F
Rationale: Standard design uses a 20°F temperature difference.
5. What is the purpose of an air separator?
A. Increase pressure
B. Remove air from system
C. Reduce flow
D. Store air
Answer: B. Remove air from system
Rationale: Air removal prevents noise, corrosion, and flow issues.
6. What is the function of a balancing valve?
A. Increase flow
B. Regulate flow
C. Reduce pressure
D. Store water
Answer: B. Regulate flow
Rationale: Ensures proper distribution of water across circuits.
7. What is the purpose of a mixing valve?
A. Increase pressure
B. Blend hot and cold water
C. Reduce flow
D. Store water
Answer: B. Blend hot and cold water
Rationale: Maintains safe and controlled supply temperatures.
8. What is the function of a boiler in hydronic systems?
A. Cool water
B. Heat water
C. Store water
D. Increase airflow
, Answer: B. Heat water
Rationale: Boilers generate heat for circulation.
9. What is the purpose of a pressure relief valve?
A. Increase pressure
B. Prevent overpressure
C. Reduce flow
D. Store water
Answer: B. Prevent overpressure
Rationale: Protects system components from excessive pressure.
10. What is the typical operating pressure of residential hydronic systems?
A. 5 psi
B. 12–15 psi
C. 30 psi
D. 50 psi
Answer: B. 12–15 psi
Rationale: Standard residential systems operate in this range.
11. What is the function of a zone valve?
A. Increase flow
B. Control flow to zones
C. Reduce pressure
D. Store water
Answer: B. Control flow to zones
Rationale: Allows independent temperature control in different areas.
12. What is the purpose of radiant floor heating?
A. Increase airflow
B. Provide even heat distribution
C. Reduce pressure
D. Store heat
Answer: B. Provide even heat distribution
Rationale: Radiant systems heat surfaces evenly for comfort.
Questions and Correct Answers (Verified Answers)
Plus Rationale 2026/2027 Q&A | Instant Download
1. A hydronic heating system requires 60,000 BTU/hr. What flow rate is needed with a
20°F temperature drop?
A. 3 GPM
B. 6 GPM
C. 9 GPM
D. 12 GPM
Answer: B. 6 GPM
Rationale: GPM = BTU ÷ (500 × ΔT) = 60,000 ÷ (500 × 20) = 6 GPM.
2. What is the purpose of an expansion tank in hydronic systems?
A. Increase pressure
B. Absorb thermal expansion
C. Reduce airflow
D. Store heat
Answer: B. Absorb thermal expansion
Rationale: Expansion tanks accommodate volume changes as water heats and expands.
3. What is the function of a circulator pump?
A. Heat water
B. Move water through system
C. Increase pressure only
D. Store water
Answer: B. Move water through system
Rationale: Circulators ensure continuous flow in hydronic loops.
4. What is the typical temperature drop (ΔT) for hydronic heating systems?
A. 5°F
B. 10°F
,C. 20°F
D. 40°F
Answer: C. 20°F
Rationale: Standard design uses a 20°F temperature difference.
5. What is the purpose of an air separator?
A. Increase pressure
B. Remove air from system
C. Reduce flow
D. Store air
Answer: B. Remove air from system
Rationale: Air removal prevents noise, corrosion, and flow issues.
6. What is the function of a balancing valve?
A. Increase flow
B. Regulate flow
C. Reduce pressure
D. Store water
Answer: B. Regulate flow
Rationale: Ensures proper distribution of water across circuits.
7. What is the purpose of a mixing valve?
A. Increase pressure
B. Blend hot and cold water
C. Reduce flow
D. Store water
Answer: B. Blend hot and cold water
Rationale: Maintains safe and controlled supply temperatures.
8. What is the function of a boiler in hydronic systems?
A. Cool water
B. Heat water
C. Store water
D. Increase airflow
, Answer: B. Heat water
Rationale: Boilers generate heat for circulation.
9. What is the purpose of a pressure relief valve?
A. Increase pressure
B. Prevent overpressure
C. Reduce flow
D. Store water
Answer: B. Prevent overpressure
Rationale: Protects system components from excessive pressure.
10. What is the typical operating pressure of residential hydronic systems?
A. 5 psi
B. 12–15 psi
C. 30 psi
D. 50 psi
Answer: B. 12–15 psi
Rationale: Standard residential systems operate in this range.
11. What is the function of a zone valve?
A. Increase flow
B. Control flow to zones
C. Reduce pressure
D. Store water
Answer: B. Control flow to zones
Rationale: Allows independent temperature control in different areas.
12. What is the purpose of radiant floor heating?
A. Increase airflow
B. Provide even heat distribution
C. Reduce pressure
D. Store heat
Answer: B. Provide even heat distribution
Rationale: Radiant systems heat surfaces evenly for comfort.
