Install Instructions

98 103448-08- 9/16
X. Operation (continued)
Table 27: Frost Protection
C. Boiler Protection Features
1. Supply Water Temperature High Limit
The boiler is equipped with independent automatic
reset and a manual reset high limit devices. A supply
manifold mounted limit device provides the automatic
reset high limit. The automatic high limit is set to
200°F (93.3°C). The control monitors a supply water
temperature sensor that is also mounted in the supply
water manifold and an internal, manual reset high limit
If the temperature exceeds 210°F (98.9°C), a manual
reset hard lockout results. If the boiler is responding to
the internal Multiple Boiler Control Sequencer, Header
Sensor or, an External EMS demand, and the supply
water temperature increases above 190° F (87.7° C),
the control begins to reduce the blower maximum speed
setting and the temperature increases to 200° F (93.3°
C), a forced recycle results. Additionally, if the supply
temperature rises faster than the degrees Fahrenheit
per second limit, a soft lockout is activated.
2. High Differential Temperature Limit
The Control monitors the temperature difference
between the return and supply sensors. If this difference
exceeds 43°F (23.9°C), the control begins to reduce
the maximum blower speed. If temperature difference
exceeds 53°F (29.4°C), a forced boiler recycle results.
If the temperature difference exceeds 63°F (35°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.
3. Return Temperature Higher Than Supply
Temperature (Inversion Limit)
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 ve times, the boiler manual reset Hard Lockout is
set. This condition is the result of incorrectly attaching
the supply and return piping.
4. External Limit
An external limit control can be installed between
terminals 11 and 12 on the low voltage terminal strip.
Be sure to remove the jumper when adding an external
limit control to the system. If the external limit opens,
the boiler will shut down and an open limit indication
and error code are provided. If the limit installed is a
manual reset type, it will need to be reset before the
boiler will operate.
5. Boiler Mounted Limit Devices
The Control monitors individual limit devices:
pressure switch, high limit device, condensate level
switch, Thermal Link (ALP285B only), Burner Door
Thermostat with manual reset (ALP285B only) and
external limit (optional). If any of these limits open,
the boiler will shut down and an individual open limit
indication is provided.
6. Stack High Limit
The Control monitors the ue gas temperature sensor
located in the vent connector. If the ue temperature
exceeds 184°F (84.4°C), the control begins to reduce
the maximum blower speed. If the ue temperature
exceeds 194°F (90.0°C), a forced boiler recycle results.
If the ue temperature exceeds 204°F (95.6°C), the
control activates a manual reset Hard Lockout.
7. Ignition Failure
The Control monitors ignition using a burner mounted
ame sensor. In the event of an ignition failure, the
control retries (ALP080B through ALP285B) 5 times
and then goes into soft lockout for one hour.
8. Central Heating System Frost Protection
When enabled, Frost Protection starts the boiler and
system pump and res the boiler when low outside air
and low supply water temperatures are sensed. The
Control provides the following control action when
frost protection is enabled:
Device
Started
Start
Temperatures
Stop
Temperatures
Boiler & System
Pump
Outside Air < -22°F (-30°C)
Supply Water < 45°F (7.2°C)
Outside Air > -18°F (-28°C)
Supply Water > 50°F (10°C)
Boiler Supply Water < 38°F (3.3°C) Supply Water > 50°F (10°C)
FROST PROTECTION NOTE
The Control helps provide freeze protection for the boiler
water. Boiler ue gas condensate drain is not protected from
freezing. Since the Control only controls 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.