Page 230

NORA Oilheat Technicians Manual

Series 10 Thermostat L2 (Hot) Burner Motor High 11-6 Primary Controls heating unit and the draft regulator. It should be centered in the flue pipe at a point where it will be exposed to flue gases between 300o and 1000oF. When the burner operates, heat rises and passes over the bimetal element, which expands and moves a shaft. This closes contacts that enable the burner to continue operating. If the bimetal is not sufficiently heated, a built-in safety switch shuts the burner off in approximately 75 to 120 seconds and it cannot be started again until the safety switch cools down and is manually reset. Wiring • The power or “hot” lead from the limit control is connected to Terminal 1. • All neutrals are connected to Terminal 2. • One wire from the burner motor and one from the oil valve, if used, are connected to Terminal 3. • If the unit operates as interrupted duty ignition, one wire from the transformer is connected to Terminal 4. • For intermittent duty ignition, connect the transformer lead to Terminal 3 along with the burner motor lead, leaving terminal 4 empty • If the control has a green terminal, it should be connected to ground. Figure 11-5. Thermostat connections If the control has two low voltage terminals for the thermostat connection, one of the thermostat wires connects to each. If the control has three low voltage terminals and the system has a two-wire thermostat, it is connected to the W and B terminals. If a 3-wire heat-only thermostat Figure 11-5: Wiring diagram for RA117A with 24v 3-wire thermostat there are many types of stack relays still operating in the field today. Fortunately, the manufacturers designed the wiring to be the same regardless of the make and model. Stack relays are typically mounted in the flue pipe, although you may occasionally find one mounted directly into the flue collector or heat exchanger. Flame detection Stack relays employ a bi-metal heatsensing element for flame detection. This heat-sensing element MUST be in the path of the combustion gases, between the Chapter 11 Primary Controls Limit L1 Power Supply, Provide Disconnect Means and Overload Protection as Required Use Green Terminal to Connect Control Case to Ground If Using a Two-Wire Thermostat, Tape Loose Ends of Red Wire (If Necessary) Contacts Break in Sequence on Temperature Rise To Replace an Intermittent Ignition Device, Connect Ignition Leadwire to Terminal 3, Instead of Terminal 4


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