Daikin WRA Installation And Maintenance Data

Daikin WRA Installation And Maintenance Data Manual pdf 30 page image

Page 30 of 44 Water to Water Source Heat Pumps IM 1072-1ControlOptional Low Temperature Control Board"LTC" – 208/230-60-3, Unit Sizes 360, 420The control board is powered by 24 volts AC, 50/60 hertzwhich is applied to the 24 VAC terminals. The control willenergize the output relays (COM 1 makes connection with NO1 and COM 2 makes connection with NO 2), only if the tem-peratures of both Sensor 1 and Sensor 2 are above the selectedtemperature which is 20°F or 35°F.Note: Always disconnect power to WW* unit before movingjumpers.While the output relays are energized, the control keepsmonitoring Sensor 1 and Sensor 2 to make sure that the tempera-ture of the sensors is always above the selected temperture, thecontrol will de-energize both ouput relays until the temperatureof the sensor is 2.5 degrees above the selected temperature. Forexample, you set the temperature to 20°F. The output relays willde-energize when the sensor temperature drops below 20°F.The control will re-energize the output relays when the sensortemperature rises above 22.5°F. Additionally, the control willmonitor each individual sensor to make sure it isn't broken orshorted. If either Sensor 1 or Sensor 2 fails short or open beforeor during operation, the control will de-energize both outputrelays until the sensor is repaired or replaced.Table 9: LTC board sensor locationsModel Sensor 1 Sensor 2WCA Liquid Out - Load Coil 1 Liquid Out - Source Coil 1WHA Liquid Out - Load Coil 1 Liquid Out - Source Coil 1WRA Liquid Out - Load Coil 1 Liquid Out - Source Coil 1Figure 10: "LTC" board jumper settings24 VAC20F35FS120F35FS2SEN 1 SEN 2NO 2COM 2NO 1COM 1AL7815DISCONNECT POWER TOWW* UNIT BEFORE MOVINGJUMPERSJumper “S1” selects cutout temperaturesetpoint for Sensor “SEN 1”.Jumper “S2” selects cutout temperaturesetpoint for Sensor “SEN 2”.The 20˚F settings are used only onclosed loop systems with antifreezesolution.Figure 11: Thermistor temperature vs. resistance graph01000020000300004000050000600007000010 20 30 40 50 60 70 80 90 100 110Thermistor Temperature Vs. ResistanceResistance (OHMS)Temperature (ºF)