Page 237

NORA Oilheat Technicians Manual

include a microprocessor in the printed circuit boards. They feature interrupted duty ignition, fifteen-second safety timing and include several new features. “Valve-delay-on” technology— depending on the manufacturer, this feature may be referred to as “valve-on-delay,” “delayed-valve-on,” or other similar wording. Through the use of an oil valve, “valve-delay-on” allows the burner motor to get up to speed delivering full flow from the fuel unit and full airflow from the fan before oil flows from the nozzle. This optimizes fuel/air mixing at start up resulting in a significant reduction of soot build-up and increased efficiency. “Motor-delay-off” technology—may also be referred to as “burner-motor-offdelay,” or other similar wording. This feature allows the motor/fan combination to continue delivering full air flow for a period of time after the oil flow through the nozzle has been cut off by an oil valve, resulting in cleaner shut downs. Did you know? Many people in our industry refer to “valve-delay-on” as “pre-purge” and “motor-delay off” “post purge.” This is not correct. The primary controls’ operations do not fit the Underwriters’ Laboratories (UL) definition of pre- and post-purge. Dry alarm contacts—These auxiliary electrical contacts close when the control goes into lock out or latch up. Through various added controls (i.e. an auto dialer) can alert the homeowner, alarm company, and/or service company of the situation. Limited reset—This feature protects against the repeated pressing of the reset button which floods the chamber with oil. If the control goes into lockout three times during a single call for heat, it goes into a restricted mode, commonly called “latch up.” The control can be reset only twice, regardless of the number of times the reset button is pressed. Instructions for removing these controls from latch-up are printed on the underside of the control where the customer cannot see them. Limited recycle—This feature limits the number of times the control will attempt to restart if the flame is repeatedly established and then lost, preventing excessive sooting from repeated combustion failure. Diagnostic LEDs—These small, lowpower lights provide a significant amount of information to help the service technician quickly and accurately diagnose the situation. Conclusion Primary controls have evolved from simple stack switches to microprocessor based controls that offer greater reliability, safety and efficiency. Control manufacturers continue to develop new products with advanced features that will make the controls in use today seem as obsolete as thermo-mechanical controls are now. As an oilheat service technician it’s important for you to be aware of these new controls so that you can continue to offer professional service to your customers. Chapter 11 Primary Controls Chapter 11—Primary Controls 11-13


NORA Oilheat Technicians Manual
To see the actual publication please follow the link above