http://www.rural-energy.net/docs/techOM_WarningLamp25.php 7 Nov 2014; 23 Oct 2015 No longer there as of Jan 2024 Oil Miser 148, BS-36UFF - 25 Second Warning Lamp ------------------------------------------------------------------------ WARNING Rural Energy Enterprises, Inc. does not accept liability for the improper use of this information. Installation, service, and maintenance of heating equipment should be performed by a qualified technician. Improper installation, adjustment, alteration, service, or maintenance can cause property damage, personal injury, or loss of life. In the event that the BS-36UFF/OM 148 water heaters are stopped by a safety device, the warning light is activated. There is a 25-second and 3-second warning lamp activation. Each time period reflects a different type of problem. The 25-second warning light is tied to the flame sensor. In this case, the flame sensor does not detect a flame (light) in the combustion chamber during the ignition cycle. The fuel pump is in electrical series with the pressure switch and electronic series with the high limit switch (on heat exchanger, upper left) and temperature fuse (on burner assembly). Ignition Sequence 1. When the power switch is on (operation lamp on) and water temperature is 5° F below set point, the blower motor and ignition transformer start operation. 2. Approximately 12.5 later, the fuel pump is activated (burner lamp on). 3. At 22.5 seconds, the flame sensor detects light in the combustion chamber. (If flame sensor does not detect light, the warning lamp will illuminate at 25 seconds.) 4. Ignition transformer stops at 34 seconds. 5. When the water reaches set point, fuel pump is turned off (burner lamp off) 6. Blower motor purges for 60 seconds and stops. 7. Water heater in stand-by condition (operation lamp on). Maintenance The water heater is a gunfired system. It is a good practice to *annually* flush the heat exchanger, clean the Empty Burn Preventative Electrode (low water cut-off), clean the flame sensor (friction fit), inspect flue and air intake, and change the main fuel filter element. Under normal residential use, the follow maintenance should be performed every *three* *years*: Three large nuts hold burner assembly on the heat exchanger. The burner assembly, fuel pump, and combustion air blower are removed as one package. To remove burner assembly disconnect fuel line from fuel pump. On main circuit board, disconnect fuel pump, flame sensor, and temperature fuse. Fuel Pump 1. Annual maintenance procedure. 2. Replace fuel nozzle. 3. Clean and set the electrodes. 4. Clean thoroughly the burn top and burner collar. 5. Vacuum combustion chamber. 6. Check fuel pump pressure. 25 second Warning Lamp When trouble shooting the 25 second warning lamp, observe the following conditions: * Does the electrode start sparking when the combustion motor starts (1 second)? * Is there a sound of combustion when the burner lamp lights (12 seconds)? * Does the fuel pump vibrate quietly or loudly (12 seconds)? Generally, five conditions will cause a 25 second warning lamp: 1. No sound of combustion when the burner lamp lights (12 sec.) and fuel pump _vibrates_ loudly. Warning lamp lights at 25 seconds. Cause: * No fuel to fuel pump. 2. No sound of combustion when the burner lamp lights (12 sec.) and fuel pump _does not_ vibrate. Warning lamp lights at 25 seconds. Causes: * *High limit switch open- manually reset* (pg. 100). * Air pressure switch open or connecting hose crimped (pg.16). There should be a wire on the two outside spades: common (lowest spade) and a N/O. No wire on middle connection. * Temperature fuse open (pg. 16). * Fuel pump failure (~ 68 ohms). Fuel pump is in series with pressure switch. * MCB failure (There should be less than 90 V at connector FP(F) when burner lamp lights). Note: See #4. Test procedure for operating system with flame sensor exposed to light. This will allow more time for taking the voltage test. The voltage at FP(F) is 120 Vac current that is diode rectified to a half wave. 3. No sound of combustion when the burner lamp lights (12 sec.) and fuel pump vibrates quietly. Warning lamp lights at 25 seconds. Causes: * MCB half wave rectifying diode failed. (Voltage should be less than 90V.) * Dirty Nozzle. * Ignition transformer failure (pg. 96). * Dirty or burned Electrodes. * Incorrect fuel pump pressure (pg. 82). * Fuel pump failure. * Air intake pipe blocked. 4. Sound of combustion when burner lamp lights (12 sec.) and fuel pump vibrates quietly. Warning lamp lights at 25 seconds or longer. Causes: * Flame sensor is not detecting light- clean and test resistance, Dark > 100 k ohms, during combustion 6 to 30 k ohms. * Fuel nozzle is partially blocked. * Burner top is covered with soot. * Air pressure switch hose is crimped. * Air pressure switch contacts are chattering. * Heat exchanger baffles are covered with soot. * Fuel pump pressure is incorrect (increase = clockwise). Test Procedure: Flame sensor * Test flame sensor for correct resistance. OR * Remove flame sensor and cover both light receiving surfaces. * Start combustion sequence. When burner lamp lights and there is sounds of combustion, expose the flame sensor to light. The water should reach set point and system should purge. * When combustion sound stops, cover the flame sensor or the warning lamp will light after the 60-second purge. Air Pressure Switch * Check connectors on air pressure switch. There should be a wire on the two outside spades: common (lowest spade) and a N/O. No wire on middle connection. * Or. Jump the two wires on the air pressure switch. _ _ 5.Unit generally functions but occasionally is found with warning lamp on. Technician cannot reproduce problem. * Eliminate fuel line restriction. * Eliminate the possibility that combustion gases are being pulled into the fresh air pipe. * Clean flame sensor and test resistance: dark = > 100 k ohms; combustion light = 6 to 30 k ohms. * Test fuel pump pressure during combustion (pg. 82). This test requires a metric tee.