Bard WG Series Installation Instructions Manual

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Bard WG Series Installation Instructions Manual Manual pdf 38 page image

Manual 2100-587JPage 38 of 5931. SEQUENCE OF OPERATION –HEATINGOn a call for heat from the thermostat, the induceddraft blower is energized. Once sufficient draft isestablished, the pressure switch contacts close andthe ignition system is energized. The direct sparkignitor will be energized allowing gas to flow. At thesame time the main valve is energized, a 30-secondblower delay timer is activated.After this delay, the heating speed blower relayenergizes. The blower will begin operating andremain in operation until the set delay timeafter the call for heat has been satisfied. Thistiming sequence guarantees blower on, blower offoperation.This unit is equipped with a flame roll-out switch,which is wired in series with the control circuit. Thisis a manual reset switch and is used for the purposeof preventing possible fire hazard in the event of asystem malfunction. If this switch has opened thecontrol circuit, there could be a possible systemmalfunction. Some of the conditions that mightcause a roll-out to occur are blockage or sooting ofprimary heat exchanger, overfiring of furnace due toimproper main burner orifices or incorrect manifoldpressure, insufficient combustion air or installationdeficiencies with respect to return air duct design orsizing.Once the problem has been resolved, reset theswitch by pressing down on the reset button onFIGURE 17Sequence of OperationElectronic Blower Controltop of the switch. See Figure 17 for additionalinformation.32. SEQUENCE OF OPERATION –COOLINGNon-EconomizerStage 1 (Y1) cooling call activates Step 1 (partialcapacity, 66%) of compressor capacity.Stage 2 (Y2) cooling call activates Step 2 (fullcapacity, 100%) of compressor capacity.With EconomizerStage 1 (Y1) cooling call goes to economizer controlsfor decision:• If enthalpy control decides outdoor conditionsare suitable for free cooling, the economizer willoperate.- If Stage 2 cooling call is issued duringeconomizer operation, the economizer willclose and the compressor will go straight toStep 2 full capacity operation.• If enthalpy control decides outdoor conditionsare not suitable for free cooling, the economizerwill not operate (or close) and Step 1 of thecompressor will operate.- If Stage 2 cooling call is issued, thecompressor will shift to Step 2 full coolingcapacity operation.Action System ResponseThermostat calls for heat(W terminal is energized).• Combustion air blower is energized.• Air proving switch makes. Airflow is established.• Ignition system is energized.• Gas valve opens and main burner lights.• Heat fan on delay timing begins. When timing is complete, the circulating fan isenergized at heat speed.Thermostat ends call for heat. • Ignition system is de-energized and gas valve closes.• Combustion air blower is de-energized after postpurge timing.• Heat fan off delay timing begins. When timing is complete, the circulating fan isde-energized.Thermostat begins call for cool(G and Y terminals re-energized).• Cooling contactor is energized.• Circulating fan is energized on cool speed after cool fan on delay timing.Thermostat begins call for fan(G terminal is de-energized).• Circulating fan is de-energizedLimit (flame rollout) opens. • Thermostat and ignition system are de-energized and gas valve closes.• Combustion air blower and circulating fan heat speed are energized.Limit (auto reset) or flame rollout(manual reset) circuit closed.• Combustion air blower remains energized for postpurge timing.• The circulation fan remains energized for the selected delay off timing.• Normal operation resumes.