Quiz 5 Flashcards
purpose of the primary control
to shut off the burner motor, oil valve, and ignition transformer in the case of flame failure
purpose of the high limit control
to protect the unit from too high temperature or pressure
define direct acting
a switch that opens on a rise in temperature pressure or liquid level
define normally closed
a switch that is closed when the circuit is at rest
define automatic reset
a switch that opens and closes due to a change in temperature, pressure or liquid level
manual reset
a switch that opens due to a change in temperature, pressure or liquid level and must be physically closed
interrupted ignition
the ignition transformer is de-energized with in 1 minute of flame detection
intermittent ignition
ignition transformer is energized during the entire run cycle of the burner
temperature sensing range of stack mounted primary
300°F to 900°F
resistance of cad cell in darkness
minimum of 50,000 Ω
resistance of cad cell in light
300 to 800 Ω
cut-out
the temperature, pressure or liquid level at which the switch will open
purpose of differential
to protect the load from short cycling
steam high limit
protect system from excessive pressure
steam high limit C/O C/I
2 PSI .5 PSI
