L404F,T,V PRESSURETROL
®
CONTROLLERS
71-2429—06
6
Fig. 7. L404F in a typical 2-wire control circuit.
Fig. 8. L404T,V terminal blocks and internal schematics.
Fig. 9. Hookup of an oil pressure controller used on a
single burner system with an integral oil pump.
Fig. 10. Hookup of an oil pressure controller used on a
single burner or multiburner system with an external oil
pump.
SETTINGS AND ADJUSTMENTS
When the pressure at the control rises above the L404
setpoint, a circuit opens between the R-B terminals. During a
pressure fall, R-B will close at the setpoint pressure minus the
switch differential.
For example, if a controller is set to differential
B
(see Fig.11)
with a controller setpoint of
A
, R-B will open when the pressure
rises to
A
. Then during a pressure fall, the R-B terminals will
close when the pressure drops to
C
(
A
minus differential
B
).
For make on rise applications, the switch is wired to R-W
terminals. The R-W circuit will close on pressure rise to the
setpoint. R-W will open again on a pressure drop past the
switch differential.
Fig. 11. Operation of switch on pressure rise and fall.
Setpoint Adjustment
Turn the pressure adjusting screw on the top of the controller
(Fig. 12) to adjust the setpoint. Turn the differential adjusting
screw to the desired pressure difference between switch
opening and switch closing.
NOTE: When the main scale setting is at the lower end of the
operating range, the differential range will be less
than the differential setting by approximately 20
percent.
M19638A
1
1
2
2
PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
AS SHOWN, SWITCH OPENS ON PRESSURE RISE. REVERSE
ACTING (MAKE ON PRESSURE RISE) UNITS ARE WIRED TO
R-W TERMINALS AND TERMINAL B IS OMITTED.
MOTOR
L404F PRESSURETROL
LINE VOLTAGE
THERMOSTAT
R
W
B
L1
(HOT)
POWER
SUPPLY
L2
L404T
BREAKS ON PRESSURE
RISE TO SET POINT
L404V
MAKES ON PRESSURE
RISE TO SET POINT
M1801B
B
R
W
R
W
B (OMITTED)
L2
OIL PRESSURE
CONTROLLER
MAIN OIL VALVE
SOLENOID
FLAME
SAFEGUARD
CONTROL
M9789
L2
L2
L1
(HOT)
OIL PRESSURE
CONTROLLER
FLAME
SAFEGUARD
CONTROL
OTHER
CONTROLLERS,
LIMITS, AND
INTERLOCKS
M9790
M19639B
B-R MAKES
(R-W BREAKS)
DIFFERENTIAL
(ADJUSTABLE)
B-R BREAKS
(R-W MAKES)
CONTROL
SET POINT
B R-W
B-R
SWITCH ACTION ON
PRESSURE RISE
INDICATES CLOSED SWITCH CONTACTS.
W
B-R
SWITCH ACTION ON
PRESSURE FALL
W
B R-W
