Weil-McLain BCP-3 User Manual

BCP-3

Blue (Output 2)

White (Output 3)

Yellow (Output 1)

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

Part Number 550-110-070/0308

Hydronic Multi-Stage Boiler Control

INSTALLATION AND OPERATION INSTRUCTIONS

Hot Water Control with

Outdoor Reset, Set
Point, and DHW for

Hydronic Applications

Boiler

SYS

Pump

DHW

Pump

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.

WARNING

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

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.

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.

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

An optional domestic hot water input is provided for systems where an indirect tank
provides DHW. During a DHW call, the BCP-3 will maintain a constant set point of
200°F or the Maximum Water Temperature setting, whichever is lower, regardless of
outdoor temperature or the status of the heating system. If 1-On/Off+2-Pumps Output
Mode option was selected, the DHW pump will be enabled whenever there is a call for
DHW. In addition, the heating system pump can be programmed to turn off during a
DHW call for up to 120 minutes to satisfy the DHW demand quicker while withholding
building heat.

Operation Concept

1:4 1:3 1:2 1:1.5

220

210

200

190

180

170

160

150

140

130

Water Temperature (in °F)

120

110

100

70 60 50 40 2030 0 -1010 -20

Outdoor Temperature (in °F)

12 11 10 9

Reset Ratio Curves

Reset Ratios are presented as

Outdoor : Water

8

7

6

5

4

3
2

1

1:1.25

1:1

1.25:1

1.5:1

2:1

3:1
4:1

8:1

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 relay while the EXT+/EXT- (Enable/Disable)
terminals are shorted using a dry-contact switch or a jumper, the System Pump relay will energize, as long as the Outdoor Sensor
reading is below the Outdoor Cutoff setting. However, upon the opening of the EXT+/EXT- (Enable/Disable) terminals or if the
Outdoor Sensor reading rises two degrees above the Outdoor Cutoff setting, all boiler relays will de-energize and the System Pump
relay will remain energized for the Run-On delay period before de-energizing.

• If DHW Priority was set to other than "NO", a DHW call using terminals T3+/T3- (DHW call Input) will de-energize the System
Pump relay for the period of the DHW priority or the termination of the DHW call, whichever comes first. This will ensure all
boiler outputs are directed to produce domestic hot water.

• If DHW Priority was set to "NO", then a DHW call will not have any effect on the System Pump relay.

DHW Pump Operation

• When the BCP-3 is controlling the DHW Pump relay by selecting "1-On/Off+2-Pump" mode from the Output Modes, a DHW
call using terminals T3+/T3- (DHW call Input) will energize the DHW Pump relay. In addition, the BCP-3 will raise the Target
temperature to the lower of 200˚F or the Maximum Water temperature Setting.

• When the BCP-3 is in Outdoor Cutoff or when the EXT+/EXT- (Enable/Disable) terminals are open, a DHW call will energize only
the DHW Pump relay in a DHW Priority setting. See Output Mode Table on page 4. However, if No DHW Priority was selected,
both the System and DHW Pumps will energize on a DHW call.

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BCP-3 Installation and Operation Manual

T

Mounting the Controller

Base Mounting Holes

• The BCP-3 is designed to mount on a 1900 (4”x4”) deep
electrical box.

• If additional room is needed for wiring use the extension
skirt provided.

• Place the BCP-3 in an indoor convenient location near
the unit to be controlled and away from excessive heat
or cold.

• Partially unscrew the Display Cover Mounting screws.
This allows for its removal.

• Lifting the Display Section away from the base starting
with the bottom will unplug it from the Base section.

• Proceed with the power and output wiring instructions.

T1 T2 T3+

COM COM

T3-

EXT+ EXT-

P+ P-

COM 24VAC

• Use the screws provided to mount the BCP-3 to the
1900 box or the extension skirt.

Input Terminals 24VAC optional power input

• Mount Display Section back to the Base Section.
Tighten the Display Cover Mounting Screws.

WARNING

The BCP-3 can accept only one source of power:
120VAC or 24VAC. If more than one power source is

Wiring

Wiring Power Input

The BCP-3 is designed to accept ONLY A SINGLE POWER SOURCE. It can be wired to
either 120VAC using the two Black wires or 24VAC using the right most two terminals on the
terminal block on bottom of the control. Weil McLain recommends the installation of a Surge
Suppressor and a Power Switch before the Power Line connection for safety and ease of service.

120VAC

• Attach line voltage, 120VAC, to the two Black wires extending from the back of the BCP-3.
Remember to use the power line from a different source than the equipment being controlled.

24VAC

• Use a dedicated transformer with at least a 5VA output.

• Bring 24VAC to the two right most terminals on the front of the BCP-3 marked 24VAC and

COM.

applied, the unit may be damaged.

Display SectionBase Section

Display Cover Mounting Screws

120VAC Power Wiring

Input Terminals

T1 T2 T3+

COM COM

{

System Sensors

T3-

{

{

Outdoor Sensor

DHW Input Dry-Contact

BLACK

120VAC Power Source

BLACK

EXT+ EXT-

P+ P-

{

Enable/Disbale Input

COM 24VAC

{

Dry-Contact

Setback Input Dry-Contact

{

24VAC power Input

Wiring Input Terminals

Heating System Sensor (HSS) Installation (T1, COM)

Locating HSS

• Place the Heating System sensor in the common header where it will register the output of the

boilers before any takeoffs.

• Only use the Standard Brass Tube sensor provided.

• The sensor wires can be extended up to 500' using a shielded 2-conductor cable (Belden #8760 or

equivalent (#18/2)).

• Cut the shield and do not connect it at the sensor end. Only connect it at the control end using the outdoor

terminal marked COM. Do not ground the shield at the sensor but at the control using the COM terminal.

• Do not run sensor wires in conduit with line voltage wiring.

Immersion Heating System Sensor (HSS) Installation

• Install a 3/8"ID x 1/2"NPT immersion well.

• Insert the supplied sensor probe into the well.

Strap-On Heating System Sensor (HSS) Installation

• Strap the sensor to the pipe using a metal clamps. Do not over tighten the clamp.

• Strap pipe insulation around the sensor and the pipe.

24VAC Power Wiring

XT+ EXT-

P+ P-

COM 24VAC

24VAC

Comm

24VAC Power Source

Sensor Wiring

T1 T2 T3+

COM COM

Shield

System Temp

Shield

Outdoor Sensor

3

BCP-3 Installation and Operation Manual

T

IMPORTANT

Determining the proper location for the Outdoor Sensor is very important.
The BCP-3 will base the heat on the outdoor temperature information it
receives from this location. If the sensor is in the sun, or covered with
ice, its reading will be different from the actual outdoor temperature.

Outdoor Sensor Installation (T2, COM)

• The Outdoor Sensor must be used when Outdoor Reset is selected as the Control Mode

from the Startup menu. However, in Set Point mode, the Outdoor Sensor is optional.
When connected in that mode, it will be used as an input for the Outdoor Cutoff only.

• Only use the Weil McLain sensor included with the unit.

• Place the sensor in the shade on the north side of the building.

• Be sure the location is away from doors, windows, exhaust fans, vents, or other heat

sources.

• The sensor should be mounted approximately 10' feet above ground level.

• Mount the sensor clip base to the outside of the building. Insert the sensor in the middle

and snap close the second clip on the sensor.

• The sensor wires can be extended up to 500' using shielded 2-conductor cable.

• Cut the shield and do not connect it at the sensor end. Only connect it at the control end

using the outdoor terminal marked COM.

• Do not run sensor wires in conduit with line voltage wiring.

Sensor Clip

Outdoor Sensor

10' Minimum

Low Voltage
Sensor Wires

Wiring the Domestic Hot Water Call DHW (T3+, T3-)

• A DHW call will raise system Set Point to 200°F or Maximum Target temperature,

whichever is lower.

• When "1-On/Off+2-Pump" is selected as the Output Mode from the Startup menu, the BCP-3 can control the

operation of the Domestic Hot Water (DHW) pump using Output 3. See Output Mode Table on page 4.

DHW Call

Wiring

• DHW Call terminals are dry contact N.O. terminals.

1 T2 T3+

• Wire an aquastat or another control to provide dry contact closure on the DHW Call terminals.

COM COM

T3-

EXT+ EXT-

Wiring the Enable/Disable (TSTAT) (EXT+, EXT-)

• The EXT terminals can be used to enable or disable the heat to the system by connecting it to a thermostat,
external control, or a switch. It accepts dry contact input only.

• If no thermostat or control is connected to the EXT terminals, leave the jumper supplied connected.

• No outputs will be active unless the EXT terminals are closed/shorted.

Enable/Disable

Wiring

Wiring the Setback/Boost (P+, P-)

• The Setback feature can be used to provide the BCP-3 with a lower temperature Set Point when less heat is

required during night or unoccupied periods.

• The Setback is activated by closing/shorting the P+ and P- terminals using an external control, i.e. timer or

switch.

COM

T3+

T3-

EXT+ EXT-

P+ P-

COM

Wiring Outputs

Wire Colors and Output Lights

• The BCP-3 has a three S.P.S.T. (N.O.) output relays. Each relay is rated at 1A Inductive load (1/8 HP).

• The BCP-3 has three LED lights that follow the output relays' operation. When a relay energizes, its LED

will turn on. When the relay de-energizes, its LED will turn off.

• The outputs are dry contacts only. They do not source any power.

• The two Yellow wires represent Output 1 relay and the left LED.

• The two Blue wires represent Output 2 relay and the middle LED.

• The two White wires represent Output 3 relay and the right LED.

• Depending on the Output Mode of operation selected during the Startup, the function of each

output will vary. See Output Mode Table for output wire colors and functions on page 4.

Boiler

Output 1 Output 2 Output 3

Setback/Boost

Wiring

+ T3-

EXT+ EXT-

SYS

Pump

P+ P-

COM 24VAC

DHW

Pump

4

BCP-3 Installation and Operation Manual

Output Mode Table

Output 1

Output Mode Description

(Yellow

Wires)

1-On/Off+1-Pump One On/Off boiler and a System pump Sys Pump Boiler Not used

1-On/Off+2-Pump

One On/Off boiler, a System pump and

a Domestic Hot Water Pump

Sys Pump Boiler

2-On/Off+1-Pump Two On/Off boilers and a System pump Sys Pump Boiler 1 Boiler 2

1-Lo/Hi+1-Pump One Lo/Hi boiler and a System pump Sys Pump Boiler Lo Boiler Hi

3-On/Off Three On/Off boilers and NO pumps Boiler 1 Boiler 2 Boiler 3

Output 2

(Blue

Wires)

Output 3

(White
Wires)

DHW

Pump

Notes

DHW Pump

controlled by DHW

Aquastat

DHW Pump

controlled by DHW

Aquastat

Sys Pump controlled

using other controls

or run constantly.

Wiring the Boiler Output

Single-Stage (On/Off) Boiler Wiring

• If any of the "1-On/Off" Output Modes is selected, wire the two Blue wires to the boiler circuit.

• If more than one On/Off boiler is to be controlled by the BCP-3, follow the wiring colors as per

the Output Mode Table above.

• The BCP-3 does not source any output power to the boiler. The relay makes when energized.

Two-Stage (Lo/Hi) Boiler wiring

• Wire the two Blue wires to the boiler control circuit initiating the Low Fire signal.

• Then, wire the two White wires to the High fire circuit.

• The BCP-3 does not source any output power to the boiler. The relay makes when energized.

Wiring the System and DHW Pump Outputs

System Pump Wiring (Not Available With "3-On/Off" Output Mode)

• The BCP-3 will control the System Pump relay (Maximum of 1/8 HP) in all Output Modes

except (3-On/Off), as all outputs will be used by boiler stages. In this scenario, the system pump
can be controlled independently using a switch or left to run constantly.

• Wire the two Yellow wires to the System Pump circuit.

• The BCP-3 does not source any output power to the pump. The relay makes when energized to

switch the power to the pump on.

DHW Pump Wiring (Available Only With "1-On/Off+2-Pumps" Output Mode)

• The BCP-3 will control the DHW Pump relay (Maximum of 1/8 HP) only in (1-On/Off+2-Pump)

Output Mode. In the other modes, the DHW pump can be controlled using an external DHW
aquastat.

• If the BCP-3 is controlling the DHW pump, wire the two White wires to the DHW Pump circuit.

• The BCP-3 does not source any output power to the pump. The relay makes when energized to

switch the power to the pump on.

On/Off Boiler

Output Wiring

Blue

Two-Stage Boiler

Output Wiring

Blue (Lo Fire)

White (Hi Fire)

System Pump
Output Wiring

YELLOW

LN

120VAC

DHW Pump

Output Wiring

WHITE

LN

120VAC

5