Boiler Control Instruction & Operation Manual, Rev 1
Page 7 of 64
Product Features
Boiler Protection Features
Supply Water Temperature High Limit
The Control is equipped with internal operating
control and high limit features. The Control
monitors a dual element temperature sensor that
is mounted in the supply water manifold and
provides UL353 and UL1998 internal safety
algorithms. If supply water temperature increases
above the active setpoint plus diff above, default
180°F (82°C) (maximum setting 190°F (88°C)) the
boiler is cycled off. If the temperature exceeds
200°F (99°C), a manual reset hard lockout results.
Additionally, the supply temperature is monitored
by a L4008A High Limit Aquastat set to recycle the
boiler at 195°F with a 5°F differential.
Stepped Modulation
While the boiler is a slave responding to the
internal Multiple Boiler Control Peer-Peer Network,
an Energy Management System (EMS) demand,
or has Header sensor selected as Central Heat
Modulation Sensor the Control still monitors
supply water temperature to prevent boiler over
firing. The boilers maximum modulation is
reduced from 100 to 0% if the supply water
temperature increases from 190°F (88°C) to 200°F
(93°C). If supply water temperature exceeds
200°F (93°C) a forced recycle results.
Sequence Master Stop All Boilers
All boilers are stopped without delay if the Call for
Heat input is removed or if the header temperature
is higher than 195°F (90.6°C) (field adjustable).
High Differential Temperature Limit
The Control monitors the temperature difference
between the return and supply sensors. If this
difference exceeds 80°F (45°C) the control begins
to reduce the maximum blower modulation. If
temperature difference exceeds 90°F (50°C) a
forced boiler recycle results. If the temperature
difference exceeds 100°F (56°C) the control will
shut the unit down. The unit will restart automatically
once the temperature difference has
decreased and the minimum off time has expired.
If the differential temperature exceeds the 100°F
limit ten times the boiler manual reset Hard
Lockout is set. Additionally, if the supply
temperature rises faster than the 4°F (2°C) per
second limit, a soft lockout is activated.
Return Higher Than Supply Temperature
The Control monitors the supply and return
temperature sensors. If the return water
temperature exceeds the supply water
temperature for longer than a limit time delay, the
Control shuts down the boiler and delays restart.
If the inverted temperature is detected more than
five times the boiler manual reset Hard Lockout is
set. This condition is the result of incorrectly
attaching the supply and return piping.
Stack High Limit
The Control monitors a dual element temperature
sensor that is mounted in the boiler vent connector
and provides UL353 and UL1998 internal safety
algorithms. If the flue temperature exceeds 210°F
(99°C), the control begins to reduce the maximum
blower modulation. If the flue temperature exceeds
220°F (104°C), a forced boiler recycle results. If
the flue temperature exceeds 230°F (110°C), the
boiler manual reset Hard Lockout is set.
Ignition Failure
The Control uses an external igniter. The Control
monitors ignition using a burner mounted flame
sensor. In the event of an ignition failure, the control
will recycle. If ignition fails after a single retry, a
manual reset Hard Lockout is set.
Central Heating System Frost Protection
When enabled, Frost Protection starts the boiler and
system pump and fires the boiler when low
outside air and low supply water temperatures are
sensed. Outdoor Air setpoint is field adjustable.
The Control provides the following control action
when frost protection is enabled:
Device
Start
Temperatures
Stop
Temperatures
Boiler &
System
Pump
Outside Air < 32°F
Supply Water < 45°F
Outside Air > 36°F
Supply Water > 50°F
Boiler
Supply Water < 38°F
Supply Water > 50°F
Table 4: Frost Protection
FROST PROTECTION NOTE
The Control helps provide freeze protection for
the boiler water. Boiler flue gas condensate
drain is not protected from freezing. Since the
Control may only cycle the system and boiler
circulators individual zones are not protected.
It is recommended that the boiler be installed in
a location that is not exposed to freezing
temperatures.
