IC "A" School Airflow, H2S, Refrigerant Practice Test 2026 – All-in-One Guide to Master Your Certification!

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What does DS1 indicate if it is extinguished?

A loss of 115 VAC external power

DS1 is a status indicator that lights when 115 VAC external power is available. If DS1 is extinguished, it means there is no external power reaching the system, so the power supply has been lost. The indicator going dark specifically points to a loss of 115 VAC external power rather than a sensor fault, nuisance alarm, or a reset request. When power is restored, DS1 should light again, confirming the power is back.

A fault in the airflow sensor

A nuisance alarm condition

A request to reset the system