L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT
A separate electromechanical high-limit is not required in
a system that uses this control to meet Underwriters
Laboratories Inc. requirements for oil-fired boiler
assemblies, UL 726.
On the L7224 models, the High Limit, Low Limit, Low Limit
Differential, and Anti Short-Cycle time can be adjusted to
the setting recommended by the boiler OEM. On the
L7248 models, the High Limit, and Anti Short-Cycle time
are also adjustable, see "Adjusting Settings".
The overall range of the High Limit is from 130 °F to
240 °F (54 °C to 116 °C). Select devices may have
different ranges. Some models have limited ranges on the
High Limit setpoint; this limited range is listed on the
Some models also have a Low Limit and Low Limit
Differential adjustment. The range of the Low Limit is from
110 °F to 220 °F (43 °C to 104 °C). Select devices may
have different ranges.
The Zr setting can be set to DHW, Zoning, or for tankless
coil applications depending on the L7224/L7248.
If an Outdoor Reset Module is installed, the reset curve
can be set by entering the minimum outdoor temperature,
minimum (boiler) temperature, and maximum outdoor
temperature on the 3-digit display. The range of the
minimum outdoor temperature is from -40 °F to 40 °F (-
40 °C to 4.4 °C) and has a default setting of 0 °F (-18 °C).
The range of the maximum outdoor temperature is from
30 °F to 70 °F
(-1.1 °C to 21.1 °C) and has a default setting of 40 °F. The
range of the minimum (water or boiler) temperature is
from 80 °F to 180 °F (26.7 °C to 82.2 °C) and has a
default setting of 130 °F. See the "Outdoor Reset Module"
Installation Instructions (form number 69-2335) for more
information on setting the boiler reset curve and all related
The L7224A,C and L7248A,C,L are designed for use with
24 Vac electronic and electromechanical thermostats or
EnviraCOM™ enabled thermostats, and have screw-type
terminals for easy field connection.
To discourage unauthorized changing of Aquastat
settings, a procedure to enter the ADJUSTMENT mode is
required. To enter the ADJUSTMENT mode, press the
UP, DOWN, and I buttons (Refer to Fig. 5) simultaneously
for three seconds. Press the I button until the feature
requiring adjustment is displayed:
Table 3. Adjustable Features.
High Limit Differential.
Low Limit. (L7224A, C)
Low Limit Differential (L7224A, C)
External Low Limit (L7248L only)
ZR input configured as external Domestic Hot
Water (DHW) request (ON/OFF) (L7224A,C/
Anti Short-Cycle Timeout (seconds); "OFF" is
Outdoor Temperature Low (minimum)
parameter for the outdoor reset curve (°F or °C)
Outdoor Temperature High (maximum)
parameter for outdoor reset curve (°F or °C)
Boiler Temperature Low (minimum) parameter
for outdoor reset curve
Boost Period (minutes). "OFF" is displayed if
Boost is inactive
Boost step (°F or °C) shown only if Boost is
Warm Weather Shutdown Temperature
(°F or °C)
Thermal Purging Limit Temperature (°F or °C),
"OFF" if disabled
Termal Purging Time Delay (minutes), shown
only if tPL is enabled
Pump Cycling (ON / OFF)
Temperature units (°F or °C)
* Settings available for adjustment on the 3-digit display
only if a W8735Y1000 or W8735S1000 Outdoor Reset
Kit is installed.
**Settings available for adjustment only when the
W8735Y1000 or W8735S1000 Outdoor Reset Kit is
Then press the UP and/or DOWN buttons to move the set
point to the desired value, to change between °F and °C,
or to enable (On) or disable (Off) the External Low Limit.
After 60 seconds without any button inputs, the control will
automatically return to the RUN mode.
In the RUN mode, the Aquastat will flash "bt" (boiler temp)
followed by the temperature (i.e., 220), followed by °F or
To read boiler settings, press the I key to read the
parameter of interest. For example, press I and High Limit
(HL) is displayed, followed by a three-digit number, i.e.,
220, followed by °F or °C. Pressing the I button again (on
L7224 models) will display the Low Limit (LL) followed by
a three-digit number and the corresponding degree
designator. See Display Readout, Table 4.
After approximately 60 seconds without any key presses,
the display will enter a dim display mode. To return to the
bright display mode, simply press any key.