The steam heated preheater and its...

Question 1 of 270705eccef9dbacbc34ba4d45ecb

The steam heated preheater and its associated pneumatic control valve are controlled by what device in the class "A" air conditioning system shown in the illustration as used condition the air of large public spaces? See illustration GS-RA-09.

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Question 1 of 27070

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🔍 Key Concepts

• Follow the pneumatic control line from the steam preheater valve to see which sensing device it connects to. • Understand the difference between a room thermostat (senses space temperature) and a duct thermostat (senses air temperature in the duct). • Notice where the diverting relay and humidistat are located in the diagram and which coils or valves they influence.

💭 Think About

• On the diagram, which symbol is directly connected (by a control line) to the pneumatic valve on the steam line feeding the preheater? • Is the preheater’s job to control the temperature in the room itself, or to maintain a minimum air temperature in the duct before it reaches the cooling coil? • Do the diverting relay or humidistat have any control lines drawn back to the preheater area, or are they only associated with the downstream reheat/space controls?

✅ Before You Answer

• Verify which device’s symbol is upstream in the duct, near the outside/mixed air and preheater coil. • Confirm that the control line from the preheater’s pneumatic valve goes directly to a temperature-sensing device in the duct, not to the devices located in the room/space. • Make sure you can distinguish the legend symbols for room thermostat, duct thermostat, diverting relay, and humidistat before choosing.