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Operating information
The control monitors the temperature difference between
the inlet and the outlet sensor. If this difference exceeds
55°F the control will reduce the maximum fan speed. If
the temperature difference exceeds 60°F the control will
shut the unit down. The unit will restart automatically once
the temperature difference has dropped below 55°F and the
minimum off time has expired.
Freeze protection
DO NOT install the boiler in a room likely to freeze.
The following integral feature of the boiler control module
provides some protection for the boiler only -- not for the
system.
The boiler control module provides freeze-up protection as
follows:
•
Below 45°F, the boiler and system pumps operate
constantly.
•
Below 37°F, the boiler turns on.
• Boiler and pumps turn off if boiler water
temperature rises above 45°F.
This feature of the boiler control module
does not eliminate the possibility of freezing.
The installation must still use recognized
design, installation and maintenance practice
to prevent freeze potential for the boiler and
system.
CAUTION
Monitor external limits
Connections are provided on the connection board for external
limits such as a flow switch or low water cutoff. The boiler
control will shut off the burner and inhibit relighting whenever
any of these external limits open.
Boiler temperature regulation
Operating temperature (target)
The boiler control module senses water temperature and
regulates boiler firing rate to achieve a target temperature. The
target temperature is calculated as described in this section
under
"Outdoor Reset Operation"
when the outdoor sensor is
connected. The maximum target temperature can be limited by
the user using the space heating set point. This temperature can
be set between 32°F and 190°F. If the outdoor sensor is shorted
or not properly installed, the target temperature is fixed at the
space heating set point.
High limit operations
The Cadet heating boiler is equipped with an adjustable
automatic reset high limit and a fixed manual reset high
limit. The automatic reset high limit has a maximum set
point of 200°F and the manual reset high limit has a set point
of 210°F.
When the outlet temperature exceeds 200°F, the automatic
high limit action occurs. The boiler shuts down until the
outlet water temperature cools below 190°F, and a 60 second
timer has expired. If the outlet temperature continues to
increase, the manual reset high limit action will occur at
210°F.
High limit setting procedure
1. Turn ON the main power to the boiler by placing the
ON/OFF switch in the ON position.
2. If boiler status reads [OFF] place the boiler into
the active position by pressing the UP
key for 5 seconds.
3. Press ENTER plus the DN button for 5 seconds.
4. Press the ENTER button until [P90] appears.
5. Press the UP/DN button to change the high limit set
point.
6. Press ENTER three (3) times to save the new parameters
(or Control Time Out will save automatically).
Please note that the brackets ([]) denote
screen status.
NOTICE
NOTICE
When system return temperatures
are maintained below the dew point,
condensation will form on the inside of the
boiler jacket causing some internal sheet
metal components to rust.
Installation & Service Manual
Low water cutoff protection
1. The boiler control module uses temperature sensing of
both supply and return ports of the heat exchanger. If the
flow rate is too low or the outlet temperature too high,
the control module modulates and shuts the boiler down.
This ensures boiler shutdown in the event of low water or
low flow conditions.
2. Some codes and jurisdiction may accept these integral
features of the control in lieu of requiring an additional
limit control or low water cutoff. Consult local
jurisdiction to determine. A low water cutoff is available
from the factory (WTR20009).
Outdoor reset operation
Target temperature with outdoor reset
This feature improves the system’s efficiency by reducing
boiler water set point as the outdoor temperature warms up.
Reset curve
The reset curve looks at outdoor air temperature and
automatically adjusts boiler water temperature in relation to
heat demand based on the settings of P01 and P02 parameters.
Outdoor air shutdown
Outdoor air shutdown specifies the outdoor air temperature
at which there is no longer a space heating demand.
