Settings and Adjustments, Setpoint Adjustment

L404F,T,V PRESSURETROL® CONTROLLERS

L404T

B (OMITTED)

L404V

B	R-W	B R-W
	CONTROL
	SET POINT
B-R BREAKS
(R-W MAKES)	DIFFERENTIAL
	DIFFERENTIAL
	(ADJUSTABLE)
		B-R MAKES
		(R-W BREAKS)
B-R W		B-R W
		B-R W
SWITCH ACTION ON		SWITCH ACTION ON
PRESSURE RISE		PRESSURE FALL

BREAKS ON PRESSURE	MAKES ON PRESSURE
RISE TO SET POINT	RISE TO SET POINT
	M1801B

Fig. 8. L404T,V terminal blocks and internal schematics.

OIL PRESSURE	MAIN OIL VALVE
CONTROLLER	SOLENOID
FLAME
SAFEGUARD
CONTROL
L2
	M9789

Fig. 9. Hookup of an oil pressure controller used on a

single burner system with an integral oil pump.

	OTHER
	CONTROLLERS,
OIL PRESSURE	LIMITS, AND

INDICATES CLOSED SWITCH CONTACTS.	M19639B

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.

DIFFERENTIAL

PRESSURE ADJUSTING SCREW

ADJUSTING SCREW

	CONTROLLER	INTERLOCKS
	L1	FLAME
	L1	SAFEGUARD
	(HOT)	SAFEGUARD
	(HOT)	CONTROL
		CONTROL
	L2	L2
		M9790

SCALEPLATES

MAIN SCALE PRESSURE INDICATOR

GROUND SCREW

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.

DIFFERENTIAL

SETTING

INDICATOR

DIAPHRAGM	OPERATING
ASSEMBLY	LEVER
	M19640A

Fig. 12. view of L404 PressureTrol® Controller.

Scaleplate Adjustment

The L404F,T,V has been carefully calibrated during manufacture and should not require recalibration.

However, if recalibration is necessary, remove the cover and loosen the setscrews which hold the scaleplate. Adjust the plate up or down, as required, to bring the device into calibration. Tighten the setscrews securely and replace the cover.

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