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NORA Oilheat Technicians Manual

Chapter 15—Service Procedures 15-5 you get to the burner, read the service card on the unit to see what work previous technicians have performed. Step 2. The investigation: At this point, you know what the problem is (no heat) and what work has been recently performed. Now is time to narrow down your investigation. Assume that you find the primary control is off on safety. You know that in an oilheat system, electricity flows from the circuit breaker to a switch to the limit controls to the primary control to the burner components. Since the control is off on safety, you can eliminate everything from the primary control back—the limit controls, switches or circuit breaker cannot have caused the problem. You have determined that the problem is probably the fuel supply, the primary control or a burner problem. There could also be a low voltage situation. Use your electrical meter to check. If the voltage is correct, move on to the next step. Step 3. Determine the problem: Next, protect the work area and remove the thermostat wires from the T-T terminals of the primary control (to prevent damage to the thermostat). Install a jumper between the terminals to simulate the thermostat calling for heat throughout the rest of the service call. Open the observation door to check for a flame or excess oil in the chamber, if there is no flame or oil, leave the door open to allow any excess pressure to escape in the event of a delayed ignition when the burner starts. Press the reset button and observe what happens: • If the burner ignites and runs properly You can protect the work area with newspaper, builder’s paper or drop cloths. Be careful when using drop cloths because they can absorb oil and cause you to bring a mess and odors to your next call. but shuts off on safety, you should visually check the cad-cell eye and leads; and check the retention head for carbon build up. If the eye and/or retention head is dirty, clean them and continue troubleshooting to determine why they’re dirty. • If the eye and head are clean, disconnect the cad cell leads from the control, start the burner and install a 1,000-ohm resistor across the F-F terminals to simulate a fire and connect your ohmmeter to the disconnected leads to check the resistance through the cad cell. If the resistance is high, the cell is either defective or is not sighting the fire correctly. If the resistance is below 1,500 ohms check the leads again, either they’re crimped or the control is defective. • If the burner starts but does not ignite, you know the problem is related to the Ohmmeter connected to leads Chapter 15 Service Procedures


NORA Oilheat Technicians Manual
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