Engine : General Subjects - 1435/1128
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| It is absolutely essential that hydronic heating system hot water piping be kept free of air. Assuming that a system is initially properly filled with water, what is the primary source of air contamination? |
| A) The introduction of air via the makeup water. |
| B) The introduction of air via the expansion tank vent. |
| C) The introduction of air with the convector steam supply. |
| D) The introduction of air via the atmospheric drains tank vent. |
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| Moeen - 2026-03-16 11:21:53 Registered (2) |
| Correct Answer: A) The introduction of air via the makeup water. In a hydronic heating system, the piping must remain completely filled with water because air pockets can reduce heat transfer, cause noise, and lead to corrosion. Even when a system is initially filled correctly, the main source of air contamination later is the makeup water. Why makeup water introduces air Fresh water always contains dissolved gases, mainly oxygen and nitrogen. When this water enters the heating system and is heated, those gases come out of solution as air bubbles. These bubbles accumulate in high points of the piping and radiators, creating air pockets. Why the other options are incorrect B) Expansion tank vent – expansion tanks usually isolate or absorb pressure changes; they are not the primary air source. C) Convector steam supply – hydronic systems use hot water, not steam supply lines. D) Atmospheric drains tank vent – drains do not normally introduce air into the closed circulation loop. ✅ Therefore, makeup water is the primary source of air contamination. You can also find similar HVAC and technical question discussions on sites like ngapk.com |