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INSTALLATION AND OPERATION INSTRUCTIONS
BCP-3
Hydronic Multi-Stage Boiler Control
Blue (Output 2)
White (Output 3)
Yellow (Output 1)
Boiler
SYS
Pump
DHW
Pump
SET
SET
SYSTEM = 147F
TARGET = 150F
Output 1
2 Line Alphanumeric Display
Displays sensor values and
menu settings
Output Lights indicate
output status
Display Section Locking Screws
Black (120VAC power)
BCP-3
Output 2 Output 3
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.
Hot Water Control with
Outdoor Reset, Set
Point, and DHW for
Hydronic Applications
The BCP-3 is a multi-boiler or multi-stage outdoor reset
hydronic heating control. It establishes ambient comfort by
varying the temperature of the heating system’s circulating
hot water in response to changes in the outdoor temperature.
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