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L404A-D,F; L604A,L,M
SETTING AND CHECKOUT
SETTING
In all models, the differential is subtractive from the
main scale set point. The upper operating point is deter-
mined by the main scale set point, while the lower operat-
ing point is determined by the main scale setting less the
differential setting. The L404F and L604A (with jumper
installed), L,M have spdt switching action. Operating points
are shown in Fig. 10.
Fig. 10—L404 and L604 operating points.
L404A,C
PRESSURE
RISE
L404B,D
PRESSURE
RISE
L404F;
L604L,M
PRESSURE
RISE
L604A
PRESSURE
RISE
L404C,D AND L604L MANUAL RESET MODELS HAVE A SMALL, FIXED
1
DIFFERENTIAL. THEY CAN BE MANUALLY RESET WHEN THE PRESSURE
FALLS TO THE MAIN SCALE SETPOINT MINUS THE DIFFERENTIAL.
L604M HAS A SMALL, FIXED DIFFERENTIAL OF 3.5 PSI (0.25 kg/cm
2
OR 24.1 kPa.)
Adjust the main scale set point for the desired operating
pressure by turning the main scale adjusting screw (Fig. 11)
on the top of the case until the main scale setting indicator
is at the desired value. On an L404A,B,F with a 5 to 150 psi
2
(.3 to 10.3 kg/cm
[34 to 1034 kPa]) operating range, or an
L604A, adjust the differential setting by turning the dif-
ferential adjusting screw (Fig. 11) until the differential
setting indicator is at the desired value. L404C,D and
L604L are manual reset models: see the next paragraph.
The L604M has a fixed differential. The scaleplates are
marked psi and kg/cm
Trip-Free Manual Reset Feature
(L404C,D and L604L only)
The L404C breaks, the L404D makes, and the L604L
makes R-W and breaks R-B when the pressure rises to the
60-2150—10
MAIN SCALE SETPOINT
(SWITCH BREAKS)
SUBTRACTIVE
DIFFERENTIAL
DIFFERENTIAL SETTING
1
(SWITCH MAKES)
MAIN SCALE SETPOINT
(SWITCH MAKES)
SUBTRACTIVE
DIFFERENTIAL
DIFFERENTIAL SETTING
1
(SWITCH BREAKS)
MAIN SCALE SETPOINT
1
(BREAKS R-B, MAKES R-W)
SUBTRACTIVE
DIFFERENTIAL
DIFFERENTIAL SETTING
(MAKES R-B, BREAKS R-W)
MAIN SCALE SETPOINT
(MAKES R1-W, BREAKS R2-B)
SUBTRACTIVE
DIFFERENTIAL
DIFFERENTIAL SETTING
(BREAKS R1-W, MAKES R2-B)
2
2
.
Setting and Checkout
main scale setpoint. They will not automatically return to
their former positions. To reset one of these controllers,
wait until the pressure falls to the set point minus the
differential (Fig. 10). Then depress the manual reset lever
(Fig. 11) and release it. The controller will not be reset until
you release the manual reset lever. This prevents the con-
troller from becoming an automatic-reset device if the reset
lever is stuck, held in, or tied down.
Fig. 11—Setting a Pressuretrol
SCALEPLATES
DIFFERENTIAL
SETTING
INDICATOR
2
MAIN SCALE
SETTING
INDICATOR
1
ADJUSTABLE DIFFERENTIAL ON THE L404A,B,F; L404L WITH A 5 TO
150 PSI (0.34 TO 10.3 kg/cm
AND L604A MODELS ONLY.
2
)
TRIP-FREE MANUAL RESET LEVER ON THE L404C,D AND L604L
MODELS ONLY.
M8942
CHECKOUT
After the controller has is installed, wired, and set, test it
with the system in operation. First allow the system to
stabilize. Then observe the operation of the controller while
raising and lowering its setpoint. Pressure should increase
when the setpoint is raised and decrease when the set point
is lowered.
Also check the make and break points of the controller.
If they do not agree with a separate, accurately calibrated
pressure gauge, a slight adjustment of the scaleplate(s) may
be necessary.
Use accurate pressure testing equipment when checking
out the controller. Do not rely on inexpensive gauges. The
controllers are carefully calibrated at the factory.
8
®
Controller.
DIFFERENTIAL
ADJUSTING
1
SCREW
MAIN SCALE
ADJUSTING
SCREW
DIFF.
MAIN
50
3.5
3
12
40
.8
10
.7
2.5
.6
30
8
2
.5
6
1.5
.4
20
.3
4
1
.2
10
2
.5
.1
0
0
PSI
DIAPHRAGM
LEVELING
ASSEMBLY
INDICATOR
2
[34 TO 134 kPa] OPERATING RANGE;
MANUAL
RESET
LEVER
2
MERCURY
SWITCH
INDEX
MARK
POINTER
M8943
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