Raypak XFyre 300A Installation & Operating Instructions Manual

RESET RATIOThe control uses the four following settings to determine the reset ratio:Boiler Start (Boil START)The Boil START temperature is the theoretical boiler supply water temperature that the heating system requires when the outdoor airtemperature equals the OUT START temperature setting. The Boil START is typically set to the desired building temperature.Outdoor Start (OUT START)The OUT START temperature is the outdoor air temperature at which the control provides the Boil START water temperature tothe system. The OUT START is typically set to the desired building temperature.Outdoor Design (OUT DESIGN)The OUT DESIGN is the outdoor air temperature that is the typical coldest annual temperature where the building is located. Thistemperature is used when completing heat loss calculations for the building.Boiler Design (Boil DESIGN)The Boil DESIGN temperature is the water temperature required to heat the boiler zones when the outdoor air is as cold as theOUT DESIGN temperature.Warm Weather Shut Down (WWSD)When the outdoor air temperature rises above the WWSD setting, thecontrol turns on the WWSD segment in the display. When the control is inWarm Weather Shut Down, the Dem 1 segment is displayed if there is aheat demand. However, the control does not operate the boiler to satisfythis demand. The control continues to respond to DHW demands.Decreasing Outdoor TemperatureIncreasing Water TemperatureBoilSTARTOUTDESIGNBoil DESIGNSTARTOUT43Reset RatioThe controller uses the following four settings to cal-culate the Reset Ration (RR):For example, when using the default values, the RRis:RR = (70 - 10) / (180 - 70) = 0.55Therefore, the RR is 0.55:1 (Outdoor:Water).RESET RATIO = (OUTDOOR START – OUTDOOR DESIGN)(BOILER DESIGN – BOILER START)Fig. 38: Reset Ratio