Installation / Operation Instruction Manual

Page 30
Bradford White Corp
Boiler Minimum target is set to Boiler Minimum +
dierential/2.
2. Target Max - The boiler target maximum is
the point at which the stages will start to turn o to
maintain a maximum water temperature. The Boiler
Maximum water temperature is set by setting dip
switch #4: Boiler Maximum 210°F (O) / 190°F (On).
To ensure that the water temperature is less than
the Boiler Maximum water temperature the target is
decreased to allow the stages to cycle o by the Boiler
Maximum water temperature, Boiler Maximum target
is set to Boiler Maximum - dierential/2.
Automatic Dierential The control has the
ability to adjust the low and high of it's temperature
range (the dierential) to prevent short cycling and
maximize the lifetime of components. As the load
increases, the dierential will decrease to minimize
temperature swings. As the load decreases, the
dierential will increase to prevent short cycling.
The term 'automatic' refers to the control
adjusting the water temperature to allow the burner to
re only when the control determines that the inferred
heat load cannot be met by the residual heat of the
water in the boiler.
WWSD Operation Warm Weather Shutdown -
WWSD feature is selected via dip switch #3, WWSD
Inactive (O) / Active 70°F (On). WWSD point is
xed at 70°F. Control exits WWSD when the outdoor
temp falls to 65°F. When there is a call for HEAT
and the control is in WWSD the HEAT call will be
ignored. When there is a call for DHW and the control
is in WWSD the DHW call will be satised. WWSD
LED turns on when control detects WWSD.
Summary of Input Sensors:
1. Outdoor sensor - monitors the outside air
temperature for outdoor reset mode
2. Boiler outlet sensor -monitors the water
temperature of the boiler outlet supply
3. System Supply sensor - monitors the water
temperature of the system supply
The boiler outlet sensor is required at all times.
If the boiler outlet sensor has any fault then the control
will ash an error and turns all stages o. The system
supply sensor is optional and utilizes
primary / secondary piping. If the system supply
sensor has a fault then the control ashes an error
message and operates using the boiler outlet sensor
(system supply = boiler outlet).
Using the system Sensor:
The system sensor can be used to control the
setpoint of a primary loop in a primary/secondary
system, or can be used to control an indirect water tank
temperature. To setup the use of the system sensor, do
the following:
1. Connect the system sensor on the SYS and COM
terminals.
2. Install the sensor into a well in the location used to
control water temperature.
3. Set DIP switch jumper positions as follows:
1 ON
2 OFF
3 OFF
4 ON
5 OFF
Table 10. DIP Switch Settings
4. The system pump will only operate with a call for
heat. The HH or CH terminals must be jumpered to
run the pump constantly.
5. The boiler setpoint may now be controlled by the
potentiometer knob on the control.
6. The operating setpoint is 150°F min to 210°F max.
7. The setpoint dierential will be automatically
adjusted by the controller. The actual temperature
may overshoot the setpoint initially, but the control
logic will minimize this throughout the operating
cycles of the boiler.
6.B.2 Operating Temperature Control on
Volume Water Heaters
Volume water heaters use a simple aquastat for
2-stage or on/o control. When setting your set point
temperature keep in mind the control is sensing the
inlet water temperature. The manual reset high limit,
which is xed at 200F, senses the outlet temperature.
Based on the ow characteristics of the installation,
the controller will need to be set no higher than 175F
(200F - Delta T = Max set point). To avoid nuisance
lockouts, reduce the set point even further.
On a 2-stage controller, set the desired operating
set point. The controller has an interstage dierential
that can be adjusted from 3°F to 10°F, which allows
the user to have some control over how stage 2 and
stage 1 call for heat. See Figure 18
6.C External Boiler Operations
Use the eld interlock terminals located in the
control box area. Remove the jumper and attach your
"T-T" or "CH" demand here.