Natco F85H Fire Coil 85 200 Installation And Operation Instructions Manual
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National Combustion Co., Inc.Page 30strip labeled "input stage 1." The input for stage 2 isinitiated by closing the circuit between the 2 terminalson the terminal strip labeled "input stage 2."6.4 Sequence of OperationThe pump time delay relay will receive a signalto initiate. If the unit is pump-mounted, the pumpwill be energized. The pump terminals on the field-wiring terminals strip will energize a field pump that isproperly interlocked with the Fire Coil 85.Once the water flow switch makes, if all of thesafety interlocks are closed, the ignition module willenergize the blower(s) for a 15-second pre-purge,followed by a 40-second period to allow the ignitor toheat.The ignition control energizes the blower. Theblower pressurizes the air box (which supplies air tothe burners) and closes the normally-open contacton the airflow pressure switch. The blocked ventpressure switch senses the pressure in the exhaustplenum. This switch opens if the pressure is excessive(as an indicator of a blocked vent). When these twopressure switches are closed, voltage is sent to thePSW terminal on the ignition control, which allows theignition module to proceed with the ignition sequence.If the airflow proving circuit is not proven,ignition module will lock out. Section 6.5 describesthe result of air flow faults in more detail.When the ignition control gets the signal at thePSW terminal, it will energize its MV terminal, whichsends power to the stage one (or on/off) main valve.After a 7-second trial for ignition, the ignitorswitches to flame sense mode. If a flame is notdetected, the gas valve will close and the ignitionmodule will attempt ignition again (up to two moretimes, for a total of three attempts.) If all threeattempts fail, the ignition control will lock out.If flame is sensed, the burner will continue tofire as long as there is a call for heat, and none of thesafety circuit is interrupted.If there is a call for stage 2 on a 2-stage unit, thatvalve will be energized.If there is a loss of flame signal during asuccessful firing sequence, the ignition control willremove power from the gas valves, and then attemptto light up to two more times. If successful, the FireCoil 85 will fire normally. If unsuccessful, the ignitioncontrol will lock out.When the call for heat is satisfied, the gasvalve(s) closes, and the blower starts a 45 second post-purge. Any pump connected to the Fire Coil 85 pumptime delay relay will continue to run for the time delayperiod (dialed by the user, 0.1 to 10 minutes).6.5 Ignition Control Reaction to Air Flow /Blocked Vent Pressure SwitchAir flow and blocked vent status are continuouslymonitored by the Fire Coil 85 ignition control, at thecontrol’s PSW terminal.At the start of an ignition sequence, if the ignitioncontrol sees power at PSW for 30 seconds, but thecombustion blower has not yet been energized by thecontrol (F1 and F2). The ignition control will remainin this fault mode, with the blower off. If the power toPSW is removed while there is still a call for heat, theignition sequence will start again, but the main valveswill not be energized until PSW sees power during theignition sequence.At the start of an ignition sequence, the controlsends the combustion blower output (F1 and F2). Ifthe control does not see power at PSW for more than30 seconds, the control will remain in this fault mode,with the blower on. If proper airflow is later detectedon PSW, the control begins a pre-purge and a normaltrial for ignition.If the PSW signal is lost while the Fire Coil 85is firing, the control will immediately de-energize thegas valve terminal (MV). The blower will remain onfor the post-purge period (45 seconds), and the controlwill continue to monitor the PSW input. If the signalis detected during the post-purge period, a normal trialfor ignition will begin, starting with the 15-secondpre-purge. If the signal is not detected during the post-purge, the control will lockout with the blower off.*1 Difference between the temperatures at which the two switchesmake R-W. Adjustable from 3°F to 10°F (1.7°C to 5.6°C) on standardmodels, or from 3.6°F to 12°F (2.0°C to 6.7°C); 55°F to 175°F (13°Cto 79°C) models.*2 Two DPDT switches operate in sequence. Each switchdifferential is fixed at approximately 3°F (1.7°C) on standard models,or 3.6°F (2.0°C); 55°F to 175°F (13°C to 79°C) models.Figure 19. Honeywell L8008G. |
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