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NORA Oilheat Technicians Manual

Specific Microprocessor-Based Primary Controls The following section is intended strictly as an overview. While other manufacturers may have similar controls, these are the units that you are most likely to encounter. Also, remember that manufacturers periodically add improvements and additional features to their controls. It is critical to consult product specific literature to verify information regarding individual controls, even if they are familiar to you. The Honeywell R7184 Honeywell’s controls differ from Carlin’s. It is also extremely important to note that some Honeywell models utilize different wire color-coding. Standard features of the Honeywell R7184 include: Limited reset—This control can be reset only two times before it goes into “restricted lockout,” or latch-up mode. The reset count returns to zero each time a call for heat is successfully completed. To reset the control from latch-up, press and hold the reset button. The LED will go out. Continue holding the button for approximately 30 to 45 seconds until the light comes on again. Limited recycle—Should the flame be lost while the burner is firing, the control shuts down the burner, enters a 60 second recycle delay and then attempts a restart. During the recycle delay, the LED will flash slowly—two seconds on, two seconds off. Do not confuse this with the burner being “in lockout.” If the flame is lost three consecutive times without successfully satisfying a call for heat, the control goes into lockout and must be reset manually. Diagnostic LED—The diagnostic LED has four states: • On—flame present • Off—no flame • 2 seconds on, 2 seconds off—recycle • 1/2 second on, 1/2 second off— lockout and latch-up. The LED can also be used to check cad cell resistance. When the burner is running after the ignition has turned off, quickly press and release the reset button. Hold it for only a half-second or less. The LED will flash from one to four times depending on the cad cell resistance: • If the light flashes once—cad cell resistance is normal: 0-400 ohms • Two flashes means resistance is normal: 400–800 ohms • Three flashes is normal: 800–1600 ohms • Four flashes indicate limited resistance of more than 1600 ohms • Lockout can occur above 4000 ohms. Pump priming cycle—To facilitate priming, the control can be placed in a purge routine by pressing and quickly releasing the reset button while the ignition is on. If the control has not locked out since its last complete heating cycle, the lockout timing will be extended for up to 4 minutes and the ignition will operate in the intermittent mode for this cycle only. Communications port—Many Honeywell residential combustion controls Chapter 11 Primary Controls 11-20 Primary Controls


NORA Oilheat Technicians Manual
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