Bard W24G2DA Installation Instructions Manual

Contents

Bard W24G2DA Installation Instructions Manual Manual pdf 39 page image

Manual 2100-592CPage 39 of 6931. 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 time after thecall for heat has been satisfied. (See Tables 10-15for selectable blower off time delays.) This timingsequence guarantees blower on, blower off operation.This unit is equipped with a flame rollout switchwhich 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 might causea rollout to occur are blockage or sooting of primaryheat exchanger, overfiring of furnace due to impropermain burner orifices or incorrect manifold pressure,insufficient combustion air or installation deficiencieswith respect to return air duct design or sizing.Once the problem has been resolved, reset the switchby pressing down on the reset button on top of theswitch. See Figure 17 for additional information.32. SEQUENCE OF OPERATION –COOLINGOn a call for cooling from the room thermostat, thehigh speed blower relay will be energized as well asthe compressor contactor. Following termination of thecooling cycle, the blower motor will continue to run forone minute.See Figure 17 for additional information.The unit may be equipped with a low ambient controlfor lower outdoor temperature operation in the coolingmode. If equipped with this optional control thecondenser fan will not operate immediately uponcompressor start up, and will cycle on and off until thecondensing pressure remains above 280 PSIG.DEHUMIDIFICATION – Dehumidification is controlledthrough a humidistat and is independent of thethermostat. On a call for dehumidification mode ofoperation, the compressor, blower and three way valveof the unit are energized through circuit R-3 to providedehumidification. Dehumidification will continue untilthe humidistat is satisfied.If there is a cooling call issued through circuit R-Y, itwill cancel dehumidification sequence (de-energize thereheat valve) until the cooling call is satisfied. If thedehumidification call is still present when cooling callis satisfied, the compressor will continue to operateand the reheat valve is reenergized.Any time there is a call for heating mode of operationthrough circuit R-W1, the dehumidification mode willcancel and the system will return to heating operation.Dehumidification is delayed 45-60 seconds on start upafter any heating cycle is complete.Any time the indoor coil temperature falls below 32°,the compressor will be de-energized until the coiltemperature rises above 57°.(Refer to Section 34 for dehumidification relay logicboard.)