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Resumen del manual
This is typical of many commercial cast iron and steel tube boilers. The HI MASS setting stages on additional boilers at the slowest rate. Differential An on / off heat source must be operated with a differential to prevent short cycling. With the control, either a fixed or an auto differential may be selected. The boiler differential is divided around the boiler target temperature. The first stage contact closes when the supply water temperature is % of the differential setting below the boiler target temperature. Additional stages operate if the first stage is unable to bring the supply water temperature up to the boiler target temperature at a reasonable rate. As the supply temperature reaches % of the differential above the boiler target temperature, stages are staged off. 8 Section C1: Pump Operation Primary Pump Operation The primary pump operates under the following conditions: • The control receives a boiler demand and is not in warm weather shut down (WWSD). • The control receives a DHW demand when DHW MODE is set to 3 or 4. • The control receives a set point demand and set point MODE is set to 3. Primary Pump Purge After a demand is removed, the control continues to operate the primary pump for a period of time. The maximum length of time that the primary pump continues to run is adjustable using the Purge setting. The primary pump continues to run until either the purging time has elapsed or the boiler supply temperature drops more than a differential below the boiler minimum setting, see Figure 12. FT- 1—1 1 1 I^VfUl ^Lf® R 1- =dS Boiler Pump Operation In certain modes of operation, the control can operate the individual boiler pumps on each boiler in addition to the primary pump. The boiler pump turns on prior to the boiler firing and continues to run after the boiler is turned off. The amount of time that the boiler pump turns on prior to the boiler firing is determined by the BOIL MASS setting. If a BOIL MASS of Lo is selected, the boiler pump turns on 15 seconds prior to the boiler. If a BOIL MASS of Medium is selected, the boiler pump turns on 22 seconds prior to the boiler. If a BOIL MASS of Hi is selected, the boiler pump turns on 30 seconds prior to the boiler. However, if the control is operating based on a set point demand, the boiler pump turns on 5 seconds prior to the boiler, see Figure 13. Boiler Pump Purge The amount of time that the boiler pump continues to run after the boiler turns off is adjustable using the boiler pump purge setting (PURG Boil Pmp). SECTION D: BOILER RESET OPERATION Section D1: Boiler Reset (Standalone) Boiler Demand When operating in the stand-alone mode, a boiler demand is required in order for the control to provide heat to the heating system. A boiler demand is generated by applying a voltage between 24 and 230 V (ac) across the Boiler Demand and Common Demand terminals (6 and 7) (FIG. 14). Once voltage is applied, the Boiler Demand pointer is displayed in the LCD. If the control is not in WWSD, the control closes the primary pump contact. The control calculates a boiler target supply temperature based on the outdoor air temperature and the characterized heating curve settings. Boiler Target Temperature The boiler target temperature is determined from the characterized heating curve settings and the outdoor air temperature. The control displays the temperature that it is currently trying to maintain as the boiler supply temperature. If the control does not presently have a requirement for heat, it does not show a boiler target temperature. Instead, "—" is displayed in the LCD. Characterized Heating Curve The control varies the supply water temperature based on the outdoor air temperature. The control takes into account the type of terminal unit that the system is using. Since different types of terminal units transfer heat to a space using different proportions of radiation, natural convection and forced convection, the supply water temperature must be controlled differently. Once a terminal unit is selected, the control varies the supply water temperature according to the 9 type of terminal unit. This improves the control of the air temperature in the building. Boiler Indoor Design Temperature The indoor design temperature is the room temperature that was used in the original heat loss calculations for the building. This setting establishes the beginning of the characterized heating curve, see Figure 15 below. Room The room is the desired room temperature for the building and provides a parallel shift of the heating curve. The room temperature desired by the occupants is often different from the design indoor temperature. If the room temperature is not correct, adjusting the ROOM setting increases or decreases the amount of heat available to the building. A ROOM setting is available for both the occupied (day) and unoccupied (night) periods. Terminal Units The control provides for a selection between six different termi...
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