8
44-604 Top Mounting Liquid Level Switches
3.0
Switch Differential Adjustment
The standard differential of the single float Model T20
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 reposition-
ing the lower jam nuts on the float stem. The standard fac-
tory setting is for a minimum amount of play (gap)
between the top jam nuts and the attraction sleeve as
shown in Figure 6.
NOTE: For assistance in computing level differential change for a
specific control, consult the factory giving the model and
serial numbers of the control.
Caution:
Maximum differential adjustment is 0.50 inch.
NOTE: To widen the differential 0.50 inch, the lower jam nuts must
be set proportionately lower on the stem (i.e., in this example
0.50 inch).
Caution:
Before attempting any work on the control, pull discon-
nect switch, or otherwise assure that electrical circuit(s)
through the control is deactivated. Close operating medi-
um supply valve on controls equipped with pneumatic
switch mechanisms.
1. Determine what change in differential is necessary.
2. Make sure power source is turned off.
3. 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 5.
5. Perform system shut-down procedures as required to
relieve pressure from tank or vessel and drain off liquid
head, if required. Allow unit to cool.
NOTE: The amount of level travel between switch-on and switch-off
actuation (differential) may be field 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 6.
This setting may be increased to a maximum of 0.50"
(13 mm), as shown in Figure 7.
6. Remove switch housing assembly by loosening the enclos-
ing tube nut, which is located immediately below housing
base. Refer to Figure 5.
Float
Enclosing tube
Refer to Figures 6 and 7
Housing base
Enclosing tube nut
Conduit
connection
Switch housing
cover
Figure 5
