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These 10 free Hydronic Heat questions are organized by exam domain, so you can see how each part of the Residential & Light Commercial Hydronic Heat Certification blueprint is tested. Reveal the answer and explanation under each question.
Simultaneous steady-state readings from a water-filled heating zone are: boiler outlet 180°F, zone supply after the mixing valve 150°F, zone return 130°F, and zone flow 3.0 GPM. Required heat transfer across the zone is 36,000 Btu/h. Using Q = 500 × GPM × ΔT, with ΔT in °F, how does measured zone heat transfer compare with the requirement?
Correct answer: B - 30,000 Btu/h; 6,000 Btu/h below the requirement
During cold commissioning, the highest radiator is 25 ft above the boiler-room pressure gauge. With the circulator off, the gauge reads 18 psig. The design requires at least 4 psig at that radiator. Use 0.433 psi per foot of water elevation. What does this static-pressure check establish?
Correct answer: C - About 7.2 psig at the radiator; the stated minimum is satisfied.
After outdoor reset is commissioned on a natural-gas condensing boiler, return water is cooler and condensate flows from the intended trapped drain during firing. The rooms remain comfortable, combustion readings meet the appliance limits, and no system-water leak is found. Which response fits these findings?
Correct answer: D - Continue operation; condensation allows recovery of latent heat from the flue gas.
An installer has connected a new, undamaged diaphragm expansion tank but has not fired the boiler. At room temperature, the system pressure is 18 psig, and a gauge on the tank's air valve also reads 18 psig. The design calls for an 18 psig precharge. Before accepting the charge setting, the installer should:
Correct answer: D - Isolate and drain the tank's water side, then recheck its air pressure.
Clear water leaves the common purge drain on a new three-loop radiant manifold, yet the longest loop still gurgles and has intermittent flow. All three loops were left open during purging. The purge valves can route fill water through one loop at a time. Which change removes the competing flow paths while purging the long loop?
Correct answer: A - Close the two shorter loops and purge through the long loop alone.
A boiler feeds a hydraulic separator. Its outlet temperature stays at 170°F, but water leaving the separator for the emitters becomes cooler when additional zones open. Measurements confirm that distribution flow then exceeds boiler flow. Temperature probes are verified and heat loss from the separator is negligible. What accounts for the lower distribution supply temperature?
Correct answer: C - Cool distribution return recirculates into the supply inside the separator.
A living room's radiant floor has reached its verified maximum heat output at the floor finish's permitted surface-temperature limit, but that output is below the room's design heat loss. Flow is correctly balanced, the embedded tubing cannot be altered, and the owner will retain the finish. Which redesign meets the load without exceeding the finish limit?
Correct answer: A - Add supplemental emitter capacity for the unmet load.
A verified boiler-pressure gauge rises from 14 to 24 psig over several hours while the water remains at room temperature and all circulators stay off. The automatic makeup assembly is the only connection to a higher-pressure water supply. Which fault best explains this pattern?
Correct answer: A - Leakage past the pressure-reducing makeup valve seat
A zone valve opens fully on a heat call, but its circulator relay does not pull in. The wiring is a simple series circuit: 24 VAC transformer, valve end switch, relay coil, transformer common. A qualified technician measures 24 VAC across the end switch and 0 VAC across the coil. Power-off tests confirm an intact coil and connecting wires. The fault is localized to the:
Correct answer: B - End-switch contacts remaining electrically open
A detached garage needs an approved glycol mixture, while the house heating circuit must remain water-only at a different operating pressure. Both will receive heat from the same boiler, and each closed circuit will have its own circulator and expansion protection. Which component transfers heat between the circuits without connecting their fluids?
Correct answer: D - A suitably sized plate heat exchanger
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