L7148F ELECTRONIC AQUASTAT
®
CONTROLLER
5
68-0189—2
Fig. 3. External connections for L7148F.
ADJUSTMENT
A manual adjustment potentiometer is used to set the high
limit controller. At the maximum setpoint of 240°F (116°C), the
calibration tolerance is plus 10°F (6°C) and minus 15°F (8°C).
(Meets ASME and UL353 Standards).
(Select models available with other ranges.)
NOTE: Setpoint Range: 130°F (54°C) to 240°F (116°C).
Differential: Fixed at 10°F (6°C).
OPERATION
A system containing an L7148F Electronic Aquastat does
not require a separate high limit controller. The L7148F can
replace a Honeywell L4080 High-Limit Controller and an
R8225 Transformer. The L7148F does not provide a low limit
function. An external transformer, appropriately sized for the
specific application; a sensor, and an immersion well are
required for Aquastat¨ operation.
In the L7148F system without an advanced feature module,
the circulator is on any time there is a thermostat call for
heat. The addition of an advanced feature module may alter
operation. The burner is also on during a thermostat call for
heat unless the boiler water temperature exceeds the high
limit setting.
The L7148F Electronic Aquastat has three states of operation:
normal, high-limit and reset: (The control moves back and
forth between the normal and high-limit states, as needed.
However, the control only enters the reset state when there
is an abnormal condition such as an internal error or shorted
sensor.)
1. Normal:
The control enters the normal state when the
temperature of the boiler drops below the high limit
setting minus 10°F (-12°C). The control exits the normal
state and returns to the high limit state when the
temperature of the boiler exceeds the high limit setting.
2. High limit:
The control enters the high limit state when
the temperature of the boiler exceeds the high limit
setting. The control exits the high limit state and returns
to the normal state when the temperature of the boiler
drops to the high limit setting minus 10°F (-12°C).
3. Reset:
Detects an error condition such as an open
sensor and shuts down all outputs. The control
continues to function and automatically restarts if the
error condition is corrected.
High Limit
The high-limit switch shuts off the burner (B1, B2 output) when
the boiler water temperature exceeds the high-limit setting.
Because heating systems differ, the correct temperature
setting for each system can vary. Follow the boiler
manufacturer recommendations for the proper setting. Turn
the HIGH-LIMIT dial on the control until the desired setting is
directly below the indicator.
Sequence of Operations
The state of the burner and circulator outputs are dependent
on the thermostat input mode (On/Off) and the current
operation mode (High limit/Normal/Reset). See Table 2
Sequence of Operations.
NOTE: Table 2 applies only to the operation of the Electronic
Aquastat Controller without an advanced feature
module. Advanced feature modules provide
additional functions such as boiler temperature
display and outdoor reset of high limit. Changes in
output states and operation modes caused by these
additional functions are not included.
COM
L7148F
HIGH LIMIT DIAL
2
L1
L2
DISCONNECT
SWITCH
1
6
CIRCULATOR
TO ADVANCED
FEATURE
MODULE
TO BOILER
SENSOR
TO THERMOSTAT
OR SWITCH
CLOSURES
FOR ZONES
24V
COM
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
GROUND MUST BE AN EARTH GROUND CONNECTION.
B1 AND S1 ARE 3/16 IN. QUICK CONNECT TERMINALS.
ALL OTHER TERMINALS ARE 1/4 IN.
C, COM, Z, B2, G ARE ALL CONNECTED INSIDE DEVICE.
FOR EXTERNAL TRANSFORMER VA REQUIREMENTS,
REFER TO APPLICATION SECTION.
R IS A CONVENIENCE TERMINAL FOR 24V HOT
CONNECTION FOR USE WITH IGNITION CONTROLS.
1
2
3
4
5
6
L2X
L1X
C
R
5
M17967
OPTIONAL VENT
DAMPER PLUG
COM
BURNER
CONTROL
24V HOT
TO VALVE
OR
IGNITION
CONTROL
CIRC
C1
G
L1 C2
L2
L2X
L1X
B2
B1
R
C
R
DATA
PORT
ST
A
TUS
THERMOST
A
T
C
W
R
S1 S2
4
4
4
4
4
3
3
