Specifications

Part number 550-100-090/0809
g a s -f i r e d w a t e r b o i l e r — Boiler Manual
82
Field wiring — advanced (see Figure 98 & Figure 99) (continued)
Additional limits
The U-Control allows connection of external limit controls, both for 1.
manual reset and for automatic reset operation of the U-Control.
Manual reset of the U-Control on limit action2. — Connect exter-
nal limits across P13, terminals 1 and 2 if the U-Control is to require
manual reset when a limit opens, even if the limit re-closes. (Remove
the factory jumper when using these terminals.)
The U-Control will lockout when a limit in its manual reset
circuit opens. The U-Contol activates its alarm terminals and
shuts the boiler down until an operator manually resets the
U-Control (as explained in this manual). This reset function
can be done by a homeowner or a service technician.
Automatic reset of the U-Control on limit action3. — Connect
external limits across P13, terminals 3 and 4 if the U-Control is to
reset automatically when the limit circuit closes after a limit condition.
(Remove the factory jumper when using these terminals.)
Remote operation/modulation
The U-Control module provides terminals to input a remote 0–10 VDC 1.
operating signal. This can be provided by a separate controller if the
boiler is configured as Type 4 (SHADOW boiler mode).
Connect the 0–10 VDC signal positive terminal to P15 terminal 6, and 2.
the signal common to terminal 5.
When receiving a remote operating signal, the boiler starts when the sig-3.
nal exceeds 1.0 VDC (and shuts off if the signal drops below 0.5 VDC).
The boiler remains at low fire until the signal exceeds 2.0 VDC. Between
2.0 and 10.0 VDC, the boiler firing rate increases with the signal value,
reaching full input at 10.0 VDC.
The U-Control continues to monitor boiler temperatures, based on 4.
the values set up under Priority 1 operation. See the following section
for details.
Additional heat demand option
The U-Control module can be set up to activate another heat source 1.
using its additional heat demand dry contracts (P16, terminals 6
and 7).
Connect these terminals to call for heat from the other heat source. 2.
(See the following section to program the boiler to activate the other
source, either as the primary or secondary heat source.)
Alarm contacts (low voltage ONLY)
The U-Control’s alarm dry contact (P16, terminals 4 and 5) closes when 1.
the boiler enters lockout.
Connect these terminals for remote alarm notification.2.
Multiple boiler wiring options
The U-Control can be programmed to sequence multiple boilers or 1.
operate/modulate in tandem from a 0–10 VDC source generated by
the lead boiler or from a remote controller.
See 2. “ADDITIONAL HEAT DEMAND,” page 83 for recommended
wiring.
Outdoor temperature sensor
The U-Control provides programmable options 1.
when using an outdoor temperature sensor. This
sensor is supplied with the boiler, and can be used
if desired (not required). See the following section
for outdoor temperature options.
Mount the outdoor sensor on an exterior wall, 2.
shielded from direct sunlight or flow of heat or
cooling from other sources.
Connect the sensor leads to P10, terminals 1 and 2, 3.
as shown in the wiring diagrams. Thermostat wire
can be used to connect the sensor.
System supply & return
temperature sensors
(see Figure 4, page 11 for placement of sensors)
The boiler is also shipped with two strap-on tem-1.
perature sensors, intended for system supply and
return.
These sensors can be attached to piping up to 2.
3-inch diameter.
Thermostat wire can be used to connect these 3.
sensors.
The system supply temperature sensor allows the 4.
U-Control to regulate temperature in the system
main piping.
Locate the supply sensor at least six pipe diameters, 5.
but no further than 3 feet, downstream from the
boiler connection to the main to ensure adequate
mixing.
The system return sensor allows the U-Control to 6.
monitor and display system return temperature.
For multiple boiler applications, install a system 7.
supply temperature sensor and system return sen-
sor wired to the LEAD boiler.
The U-Control also compares the system return 8.
temperature with the system supply temperature.
Should the return temperature ever exceed the
supply temperature, the U-Control knows there is
likely a sensor failure and will report this problem
on the display.