SPL/45-94117B page 3 of 4
(BP) Latch Relay Contact Models
Primarily designed to maintain a specific temperature range by turning ON or
OFF heaters or coolers having 125 VAC circuitry, the SPLBP and 45TEBP
SWICHGAGE
®
models are applicable to a variety of situations where tempera-
tures are variable and controlling factors. As the pointer touches a preset high or
low limit contact/snap-switch, the magnetic latching relay sets or resets to latch
a heater or cooler ON or OFF. The relay unlatches, (resets) when the opposite
contact operates. Pictured below is a typical application.
For applications with higher voltages, a Murphy TR assembly can be used
in conjunction with any 4-1/2 in. (114 mm) dial SWICHGAGE
®
.
SPLC and SPLFC SWICHGAGE
®
temperature indicator gages include 2 pilot
duty, pointer-type limit contacts (one for high and one for low) that can be used
for alarm and/or shutdown. The SPLC and SPLFC models will complete a cir-
cuit when the gage pointer and either limit contact meet. This provides an elec-
trical signal to alert the operator of critical temperature conditions or, when
required, to shut-down the equipment.
Both limit contacts (high and low) are field adjustable by simply turning the
fingertip type knob to the desired point on the scale dial.
The graphic below shows details of a typical SPLFC SWICHGAGE
®
model.
The 45TE series SWICHGAGE
®
incorporates 2 SPDT snap-switches instead
of the pointer-type contacts of the SPL. Unlike the SPL that completes an elec-
trical circuit as soon as the pointer touches the contact, the 45TE trip point indi-
cators will stop the pointer movement slightly before the switches operate. As
temperature continues to increase (reaching high set point) or to decrease
(reaching low set point), the electrical circuit is then made. It provides the abili-
ty to set the trip point exactly with the indicator needle—no guessing or equip-
ment calibration is needed as on blind switches. The 45TE trip points (high and
low) can be easily set using its stacked knob adjustment. See the schematic
below for details.
How the SPL Works
How the 45TE Works
Capillary Tube
Low Limit
High Limit
Latching Relay
Terminal Block for
customer wiring
SPLBP
REMOTE COOLER
OFF
Power
Supply
ENGINE
Coolant line
TEMPERATURE
MURPHY
SWICHGAGE®
TULSA, U.S.A.
270
250
230
170
350
330
320
310
390
°
C
°
F
ON
Sensing Bulb
(not shown)
Pointer
SPL Series
High Limit
Contact
Adjustment
Dial Cutaway
to Show
Mechanism
Pointer
Low Limit
Contact
Adjustment
TEMPERATURE
MURPHY
SWICHGAGE®
TULSA, U.S.A.
270
250
230
200
170
350
600
700
800
900
°
C
°
F
45TE Series
High Limit
Snap-switch
Stacked Knob
Adjustment
Low Limit
Snap-switch
Dial Cutaway to
Show Mechanism
Pointer
High Trip Point
Indicator
Low Trip Point
Indicator
TEMPERATURE
MURPHY
SWICHGAGE®
TULSA, U.S.A.
270
250
230
200
170
350
600
700
800
900
°
C
°
F
SPLFC model shown
45TEF model shown
