64
ALTA
Combi Installation, Operating & Service Instructions
110327-04 - 1/22
Boiler Protection Features (continued)
7. Flue High Limit
Control monitors flue gas temperature sensor
located at top of heat exchanger. If flue
temperature exceeds 194°F (90°C), control
begins to reduce blower maximum speed and if
flue temperature exceeds 204°F (96°C), a forced
boiler recycle results. If flue temperature exceeds
214°F (101°C), control activates a manual reset
Hard Lockout.
8. Raised Minimum Modulation
To help prevent nuisance shutdowns following
a loss of flame while the boiler is running,
(condition that could be caused by excessive
wind) minimum modulation is increased to help
prevent additional nuisance shutdowns. Minimum
modulation increase is removed after an hour.
9. Calibration
The control measures ionization current during
burner operation to ensure a constant air fuel
ratio. An accurate ionization measurement is
maintained over time by periodically calibrating
ionization measurement.
Normal calibration is performed during CH
demand. When there is no CH demand (non-
heating seasons) calibration is periodically
initiated when boiler is cold and no demand is
present.
WARNING
Burn Hazard.
Boiler may start without DHW or CH demands
when periodic calibration is required and boiler
is cold.
10. Ignition Failure
Control monitors ignition using a burner mounted
flame sensor. In event of an ignition failure, the
control retries 2 times and then goes into soft
lockout for one hour. After a one hour soft lockout
control will retry 2 additional times before control
activates a manual reset Hard Lockout.
16
Operation
(continued)
11. Central Heating System Frost Protection
Frost Protection starts boiler and system pump
and fires boiler when low outdoor air, low supply
water or Low DHW temperatures are sensed.
Control provides following control action when
frost protection is enabled:
Table 16-19: Frost Protection Interlocks
Device
Started
Start Temperatures
Stop Temperatures
Boiler
Pump
Outdoor Air
< 0°F (-18°C)
Supply Water
< 45°F (7.2°C)
DHW Water
< 45°F (7.2°C)
Outdoor Air
> 4°F (-16°C)
Supply Water
> 50°F (10°C)
DHW Water
> 50°F (10°C)
Boiler
Supply Water
< 38°F (3.3°C)
DHW Water < 38°F
(3.3°C)
Supply Water
> 50°F (10°C)
DHW Water
> 50°F (10°C)
NOTICE:
FROST PROTECTION
The control helps provide freeze protection for
boiler water. Boiler flue gas condensate drain is
not protected from freezing. Frost protection only
controls system and boiler pumps. Individual
zones are not protected. It is required that boiler
be installed in a location that is not exposed to
freezing temperatures. Outdoor air interlocks
included when outdoor air sensor is wired to low
voltage terminal block.
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