đ Key Concepts
⢠Thermostat contacts are just temperature-actuated switches â think in terms of normally-open (NO) vs normally-closed (NC).
⢠A thermostat that opens on rising temperature is normally closed at normal (lower) temperature and opens when the set temperature is exceeded.
⢠Look for the small graphic added to the basic switch symbol that indicates temperature actuation (often a slanted line or wedge) and note whether the basic contact shown is NO or NC.
đ Think About
⢠First, among symbols 1â14, which ones clearly show a basic switch contact (NO or NC) with some extra mark indicating itâs controlled by a condition (temperature, pressure, flow, etc.)?
⢠Of those conditionâcontrolled switches, can you decide which extra mark most logically represents temperature rather than pressure or flow, by comparing to the physical thermostats shown in views C and D?
⢠Once youâve isolated the temperatureâtype symbols, look closely at the contact itself: is it drawn as closed in its normal state, or open? Remember, a thermostat that opens on rising temperature must be shown closed in its normal (lower temperature) condition.
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Before You Answer
⢠Be sure you can identify which symbols represent normally closed (NC) contacts versus normally open (NO) contacts before choosing.
⢠Confirm that the added shape (triangle, bulb, circle, etc.) matches what youâd expect for a temperature sensing element rather than pressure or flow.
⢠Before picking an answer, doubleâcheck that the symbol you chose shows a closed contact in the normal state that would open when actuated by temperature rise.