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In addition, it provides an outdoor temperature based cutoff, heating system pump control, and domestic hot water (DHW) pump control. Two unique features have been added to this control including a customized reset ratio curve. A Set Point option was added for applications where outdoor reset will not apply. Two sensors are used, one to monitor the outdoor temperature and one to monitor the circulating hot water temperature in the heating system. When the outdoor temperature falls below the outdoor cutoff setting, the heating system is activated and the target water temperature is increased proportionally to satisfy the load. Should it get warmer outdoors, the target water temperature is automatically lowered by the control. If the outdoor temperature continues to rise to the outdoor cutoff setting then the heating system is turned off. Because of the many different physical characteristics of buildings including the type of radiation; i.e., baseboard or radiant, the heat loss varies. In one building, a 1-degree outdoors temperature change may require a change of 1 degree in heating water temperature; for another it may require a change of 2, 3, or even 4 degrees in order to gain the desired comfort level. This is known as the Reset Ratio. The Reset Ratio chart shows the wide range of Reset Ratios available for the BCP-3 in addition to the customized reset ratio. See page 2. The installer fits the BCP-3 to a specific building by adjusting the Reset Ratio curve. With curve number 4 (2:1 reset ratio) a 2-degree change in outdoor temperature will change the circulating hot water temperature by 1 degree; at curve number 11(1:3 reset ratio) an outdoor change of 1 degree will change the water temperature by 3 degrees. Most buildings with baseboard radiation require a curve of 6, 7, or 8. Radiant heat applications usually require a lower curve. An external T-Stat input can be used to shut the heating system down when the WARNING This Weil McLain control is strictly an operating control; it should never be used as a primary limit or safety control. All equipment must have its own certified limit and safety controls required by local codes. The installer must verify proper operation and correct any safety problems prior to the installation of this Weil McLain control. Part Number 550-110-070/0308 BCP-3 Installation and Operation Manual thermostat is satisfied. Another, is a Setback input that will switch the heating system to a lower set point determined by the Set Back setting. 1:4 1:3 1:2 1:1.5 Type of Radiation in Building Reset Ratio Offset Radiators (Steel & Cast Iron) 1.00 (O) : 1.00 (S) 0.F Baseboard (Finned copper tube& Cast Iron) 1.00 (O) : 1.00 (S) 0.F Radiant (High Mass/Concrete) 4.00 (O) : 1.00 (S) -10.F Radiant (Low Mass/Joists) 2.00 (O) : 1.00 (S) -10.F Fan Coils & Air Handlers 1.00 (O) : 1.00 (S) 20.F 1211 10 9 220 8 1:1.25 210 200 190 7 1:1 180 6 1.25:1 170 160 5 1.5:1 150 An optional domestic hot water input is provided for systems where an indirect tank 4 2:1 140 provides DHW. During a DHW call, the BCP-3 will maintain a constant set point of 3 3:1 200°F or the Maximum Water Temperature setting, whichever is lower, regardless of 130 2 4:1 outdoor temperature or the status of the heating system. If 1-On/Off+2-Pumps Output 120 Mode option was selected, the DHW pump will be enabled whenever there is a call for 110 1 8:1 DHW. In addition, the heating system pump can be programmed to turn off during a 100 DHW call for up to 120 minutes to satisfy the DHW demand quicker while withholding Outdoor Temperature (in °F) building heat. Reset Ratio Curves Reset Ratios are presented as Outdoor : Water Operation Concept The BCP-3 has multiple Output Modes of operation. It can control any three output boiler-and-pump variety ranging from a single On/Off boiler with a system pump to three individual boilers. In addition, it can accepts a DHW call signal to raise the target set point. Moreover, if "1-On/Off+2-Pump" is selected as an Output Mode, it will control the DHW pump allowing it to energize on a DHW call. (See Output Mode Table under the Startup Menu on page 4.) Boiler Operation • When a single On/Off boiler is selected as the primary function of the BCP-3, the boiler relay will energize when the System Sensor reading is below the Target temperature less the Differential. Moreover, the Outdoor Sensor reading must be below the Outdoor Cutoff setting and the EXT+/EXT- (Enable/Disable) terminals must be shorted using a dry-contact switch or a jumper. If the System temperature exceeds the Target, the boiler relay will de-energize. • If sequencing multiple stages or boilers are the primary function of the BCP-3, the BCP-3 will use the Purge Delay to start the lead boiler. Then, it will use the Reaction Time to add additional stages or boilers. When subtracting stages, the BCP-3 will use only the Minimum Run Time. System Pump Operation • When the BCP-3 is in one of the Output Modes that control the System Pump rela...