What is the purpose of the roll-out switches?
A) to shut the gas valve off if flames roll out of the combustion area
B) to shut of the gas valve if the flames do not light within a few seconds
C) to shut off the gas valve if the air leaving the furnace becomes too hot
D) to coordinate the fan operation with the normal flame rollout on the furnace
Question 2
How is a concentric vent used in a high-efficiency furnace?
A) It creates two close exit points for the vent pipe and combustion air pipe.
B) It allows the vent pipe to combine with condensate drainage.
C) It directs the combustion air pipe to an outdoor exit.
D) It allows a single outdoor exit point for the vent and combustion air pipe.
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