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Control Board Operation
Aquastat Sensor - This sensor is located in the aqua-
stat well on the top of the water jacket. This sensor
along with the outdoor air sensor is what the control
board uses to regulate the feed rate based on these two
observed conditions. (Boiler Temp. & Outdoor Air
Temperature)
Outdoor Air Temp. Sensor (OAT) - This sensor is
located outside the building (on the north side of the
house and out of direct sunlight). The Outdoor Air
Sensor is used to perform hot water reset based on out-
door air temperatures.
When the OAT sensor is installed, at 20° F. or below
(outside temperature), the boiler will operate at the
temperature set on the MAX. TEMP. knob. The boiler
water temperature will decrease by 1 degree F. for
every 1 degree F. in temperature rise (above 20°) of
the outdoor air.
NOTE: Pellet Boiler Outdoor Air Reset Operation
Graph located on page 23.
WATER TEMPERATURE
MAX. TEMP.
MIN. TEMP.
Setting The Boiler Temperature
Without the Outdoor Air Temperature Sensor
Installed
To set the maximum boiler water temperature, sim-
ply turn the Max. Temp. water temperature dial to the
desired setting. The control and the boiler will then
perform to achieve and maintain the set temperature.
The Min. Temp. Knob is the boiler water tempera-
ture minimum, or the lowest temperature the water
will go before the unit re-starts. Turning the knob fully
counter-clockwise is the “OFF” position, while turn-
ing the knob clockwise, past the 140 degree marking,
is the “ON” position..
With The Outdoor Air Temp - Sensor Installed
Maximum boiler temp setting is as described above.
The MIN. TEMP. knob in addition to being the
mode setting (on or off) now also has the function of
setting the minimum boiler water temperature. This
would be the lowest boiler water temperature that you
want to have based on the following factors.
1.) Outdoor Air Temperature (OAT)
2.) Domestic Hot Water Use
a.) Hot Water Coil Option
b.) Indirect Hot Water Storage
3.) Overall Volume of the Heating System
The boiler is designed to withstand lower return water
temperatures however, extended return temperatures below
140 degrees F can cause condensation in the secondary
ash chamber area and also in the venting system, which
could cause damage in these areas.
NOTE:
If the system is run at the lower temperature settings, con-
ditions of the rebox, boiler tubes, secondary ash chamber
and venting should be monitored closely. If conditions show
excess condensation, the boiler water minimum tempera-
ture will need to be increased until condensation does not
occur. You should also consider some form of tempering of
the return water system. Discuss this with your plumber.