Bard WH185 Installation Instructions Manual

Manual 2100-501Page 16 of 21PRESSURE SERVICE PORTSHigh and low pressure service ports are installed on allunits so that the system operating pressures can beobserved. Pressure curves can be found later in themanual covering all models on both cooling and heatingcycles. It is imperative to match the correct pressurecurve to the unit by model number.DEFROST CYCLEThe defrost cycle is controlled by temperature and timeon the solid state heat pump control. See Figure 11.When the outdoor temperature is in the lower 40°Ftemperature range or colder, the outdoor coiltemperature is 32°F or below. This coil temperature issensed by the coil temperature sensor mounted near thebottom of the outdoor coil. Once coil temperaturereaches 30°F or below, the coil temperature sensorsends a signal to the control logic of the heat pumpcontrol and the defrost timer will start.After 60 minutes at 30°F or below, the heat pumpcontrol will place the system in the defrost mode.During the defrost mode, the refrigerant cycle switchesback to the cooling cycle, the outdoor motor stops,electric heaters are energized, and hot gas passingthrough the outdoor coil melts any accumulated frost.When the temperature rises to approximately 57°F, thecoil temperature sensor will send a signal to the heatpump control which will return the system to heatingoperations automatically.If some abnormal or temporary condition such as a highwind causes the heat pump to have a prolonged defrostcycle, the heat pump control will restore the system toheating operation automatically after 10 minutes.The heat pump defrost control board has an option of30, 60 or 90-minute setting. All models are shippedfrom the factory on the 60-minute pin. If specialcircumstances require a change to another time, removethe wire from the 60-minute terminal and reconnect tothe desired terminal. The manufacturer'srecommendation is for 60-minute defrost cycles. Referto Figure 11.There is a cycle speed up jumper on the control. Thiscan be used to reduce the time between defrost cycleoperation without waiting for time to elapse.Use a small screwdriver or other metallic object, oranother 1/4 inch QC, to short between the SPEEDUPterminals to accelerate the HPC timer and initiate defrost.Be careful not to touch any other terminals with theinstrument used to short the SPEEDUP terminals. Itmay take up to 10 seconds with the SPEEDUP terminalsshorted for the speedup to be completed and the defrostcycle to start.As soon as the defrost cycle kicks in remove theshorting instrument from the SPEEDUP terminals.Otherwise the timing will remain accelerated and runthrough the 1-minute minimum defrost length sequencein a matter of seconds and will automatically terminatethe defrost sequence.There is an initiate defrost jumper (sen jump) on thecontrol that can be used at any outdoor ambient duringthe heating cycle to simulate a 0° coil temperature. Thiscan be used to check defrost operation of the unitwithout waiting for the outdoor ambient to fall into thedefrost region.By placing a jumper across the SEN JMP terminals (a1/4 inch QC terminal works best) the defrost sensormounted on the outdoor coil is shunted out and willactivate the timing circuit. This permits the defrostcycle to be checked out in warmer weather conditionswithout the outdoor temperature having to fall into thedefrost region.In order to terminate the defrost test theSEN JMP jumper must be removed. Ifleft in place too long the compressorcould stop due to the high pressurecontrol opening because of high pressurecondition created by operating in thecooling mode with outdoor fan off.Pressure will rise fairly fast as there islikely no actual frost on the outdoor coilin this artificial test condition.There is also a 5-minute compressor timedelay function built into the HPC. This is toprotect the compressor from short cyclingconditions. In some instances it is helpfulto the service technician to override orspeed up this timing period, and shortingout the SPEEDUP terminals for a fewseconds can do this.FIGURE 11DEFROST CONTROL BOARD