Fixtures & Water Heaters第 83 / 120 题
A residence has a pressure reducing valve with a check on the incoming water service, and the 40 gallon water heater's relief valve has begun weeping each evening. What is the most likely cause and the correct correction?
a.Thermal expansion in a closed system; install an expansion tank sized for the system
b.The relief valve is set too high; replace it with a 250 degree F valve
c.The heater is oversized; reduce the thermostat to 90 degrees F
d.The discharge line is too long; shorten it and add a threaded cap
解析
A check or pressure reducing valve makes the system closed, so water expanding as it heats has nowhere to go and pressure rises until the relief valve lifts, which is corrected with a properly sized thermal expansion tank. Replacing the relief valve with a higher setting defeats the safety device rather than solving the pressure problem. Lowering the thermostat to 90 degrees F creates a bacterial growth risk, and capping the discharge line is expressly prohibited.
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