A duct that has an operating temperature of 150 deg F shall be insulated to limit the exposed surface temperature to how many degrees Fahrenheit?

Prepare for the Maryland HVAC Masters Test with engaging flashcards and multiple choice questions. Elevate your HVAC knowledge and get ready for your exam with hints and explanations!

Multiple Choice

A duct that has an operating temperature of 150 deg F shall be insulated to limit the exposed surface temperature to how many degrees Fahrenheit?

Explanation:
Insulation is used to limit heat transfer from hot ductwork and keep the exposed surface at a safe, touchable temperature. When a duct carries hot air, the surface without insulation can get very hot, so the goal is to lower that surface temperature to a practical limit. A common design limit for exposed duct surfaces is about 120°F, which provides a safe contact temperature for typical conditions. With a duct at 150°F, insulating enough to bring the surface down to 120°F achieves this safety target. A surface temperature of 100°F would require more insulation than necessary and isn’t the standard target, while 140°F or 160°F would remain hot enough to pose a burn hazard.

Insulation is used to limit heat transfer from hot ductwork and keep the exposed surface at a safe, touchable temperature. When a duct carries hot air, the surface without insulation can get very hot, so the goal is to lower that surface temperature to a practical limit. A common design limit for exposed duct surfaces is about 120°F, which provides a safe contact temperature for typical conditions. With a duct at 150°F, insulating enough to bring the surface down to 120°F achieves this safety target. A surface temperature of 100°F would require more insulation than necessary and isn’t the standard target, while 140°F or 160°F would remain hot enough to pose a burn hazard.

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