HVAC Rooftop Units Flashcards
What are the three main parts of a roof top unit?
heating, cooling, ventilation
Arerollback switches normally open or normally closed?
normally closed
What is the purpose of the ignition transformer?
make spark ignite gas
What is the purpose of a flame rod?
prove flame
the flame provides a path for current
What is the purpose of the combustion blower motor (induced draft fan)?
ensures that the flame burns properly
When a rooftop unit receives a call for heat, which component should start first?
combustion blower motor
For rooftop units that use intermittent ignition, once the pilot flame ignites, what must happen before the main flame ignites?
flame rod must sense pilot flame
Once the main flame ignites, which motor starts?
evaporator
What happens after the thermostat contact opens?
Main gas valve is de-energized
What is the difference between intermittent spark ignition and direct spark ignition?
Direct spark ignites main flame
intermittent ignites pilot flame
Which method of ignition is quicker?
DSI
When the rooftop unit receives a call for heat, which terminal point on the rooftop becomes energized first?
W1 terminal
Make up air units are normally interlocked with specific equipment. What is the equipment?
exhaust fan motor
WHat is the make up air units main function?
to supply fresh outside air
WHat kind of heating systems do two wire thermostats typically control?
home furnaces and unit heaters
