8
46-624 Series 3 Liquid Level Switches ASME B31.1 Construction
3.0
Switch Differential Adjustment
The standard differential of Series 3 float models with only
one switch mechanism may be field-adjusted. Adjustment
may be necessary if a wider differential needs to be set to
overcome switch chatter caused by the process.
The differential, or the amount of level travel between
“switch-on” and “switch-off ”, may be adjusted by
repositioning the lower jam nuts on the float stem.
This adjustment is different for high level and low level
controls. Refer to the appropriate section below for
adjustment instructions.
Caution:
Maximum differential adjustment is 1 inch (25 mm).
3.1
Low Level Controls
On low level controls the switch trips on the lower actuation
point and resets on the higher actuation point. Widening
the differential will allow the switch to trip on the original
actuation point and reset at a later, or higher, point.
The differential on low level controls may be adjusted by
repositioning the lower jam nuts on the float stem. The
standard factory setting is for a minimum amount of play
(gap) between the top jam nuts and the attraction sleeve as
shown in
Figure 7
on page 9.
1. Determine what change in differential is necessary.
NOTE: To widen the differential one inch, the lower jam nuts must be
set proportionately lower on the stem (i.e., in this example
1 inch).
2. Make sure power source is turned off.
3. NEMA 4X/7/9—Unscrew and remove switch housing
cover.
4. Disconnect power supply wires from switch mechanism.
Pull wires out of conduit connection opening in housing
base. Refer to
Figure 6
.
5a. Perform system shut-down procedures as required to
relieve pressure from float chamber of control. Allow unit
to cool.
5b. Close shut-off valves (if so equipped) to isolate control
from tank. Drain off liquid in float chamber. Refer to
Figure 3
on page 5.
5c. On installations without shut-off valves, relieve pressure
from the tank. Drain liquid in tank to a level below the
connections of the float chamber.
Float
Enclosing tube
Refer to Figures 7 and 8
Housing base
Enclosing tube nut
Conduit
connection
Switch housing
cover
Chamber
Figure 6
