DF-94063N
Revised 09-03
Section 15
Installation and Operation of the
(00-02-0170)
DF Series Hydrostatic Head Level Switches
Please read the following information before installing. A visual inspection of this product for damage during shipping is rec-
ommended before mounting. It is your responsibility to have a qualified person install this unit and make sure it conforms to NEC
and local codes.
GENERAL INFORMATION
*
WARNING
BEFORE BEGINNING INSTALLATION OF THIS MURPHY PRODUCT
**
✔ Disconnect all electrical power to the machine.
✔ Make sure the machine cannot operate during installation.
✔ Follow all safety warnings of the machine manufacturer.
✔ Read and follow all installation instructions.
CAUTION: Certain dangers to human safety and to equip-
ment may occur if some equipment is stopped without
pre-warning. It is recommended that monitored functions
be limited to alarm only or to alarm before shutdown.
Description
Specifications
Snap-switch Ratings
The DF series are diaphragm operated “hydrostatic head pressure”
level switches. A pressure sensitive diaphragm operates a snap-switch
that can be wired directly to electric pilot circuits to control pumps at
predetermined levels. Typical application is to start and stop electric
driven pump(s) to maintain tank levels. It is also applicable to engine
driven pumps.
SPDT (standard–all models)
• 5 A @ 125, 250, or 480 VAC
• 1/2 A @ 125 VDC, 1/4 A @ 250 VDC
Case/Lid: Aluminum (standard); all non-explosion proof models.
Bottom Plate: Glass-filled nylon.
The Nitrile sensing diaphragm is impervious to most liquids and is
sensitive enough to control levels with 1/4 in. (6 mm) repeatability.
See model descriptions for limits of switch trip point adjustability.
Materials include aluminum body, nylon bottom plate and a special
alloy leaf snap-switch as standard.
Process Connection: 1 NPT (standard)
Maximum Pressure Rating: 25 psi (172 kPa) [1.72 Bar].
Conduit Connection (electrical): 1/2 NPT.
Warranty
This simple level switch is highly reliable and can be worked into most
new or existing system without major modification or special tools.
A limited warranty on materials and workmanship is given with this FW
Murphy product. A copy of the warranty may be viewed or printed by going
DF755 and DF757 are suitable for atmospheric tanks in a non-haz-
ardous location.
The SPDT snap-switch for the DF755 is preset for a 4 in. (102 mm)
differential in liquid level, operating at approx. 6 inches (152 mm) ris-
ing, and resetting at approx. 2 inches (51 mm) falling level.
The DF757 trip point is adjustable over a 108 inches (2743 mm) dif-
ferential.
DF-94063N page 1 of 4
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BASIC OPERATION
DF755EX
DF755
DF757
C
C
B
C
B
B
D
Vent (DF755EX)
or Tube Fitting
(DF756)
A
A
A
Hydrostatic Head
Pressure
Hydrostatic Head
Pressure
Hydrostatic Head
Pressure
As the liquid level rises, hydrostatic head pressure is applied to the
diaphragm A. The diaphragm is forced upward forcing the actuator arm
to activate the snap-switch
Setpoint Adjustment (DF757)
1. Locate threaded adjustment shaft and adjustment
knobs (see drawing above).
B
C.
Models DF755 and DF755EX are factory set and operate at approximately
2 in. (51 mm) and 6 in. (152 mm) rising above the level at which the
diaphragm is mounted. The switch resets back to normal condition at
approx. 2 inches (51 mm) falling level. The trip point(s) for Model DF757
are adjustable between 2 in. (51 mm) and 110 in. (2794 mm) for high and
2. To increase low level setpoint, rotate lower
knob counterclockwise.
NOTE: If adjustment shaft turns
when rotating adjustment knobs,
Adjustment
Shaft
grasp the adjustment shaft with a
pair of needle nose pliers–then
rotate knob.
low (make/break) operation by knobs,
D.
For sealed tanks, model DF755EX can be fitted with a tube fitting to bal-
ance the top of the diaphragm chamber to a tank gas blanket (see Typical
Applications). The DF755EX is supplied with an atmospheric vent fitting.
USING THE DF755 WITH MAC1 VOLUME CELL ACCESSORY
The MAC1 Volume Air Cell when attached to the DF755 can monitor tion for the DF755. All fittings and connections should be air-tight to
water levels on a sump. Activate alarms or start a pump directly. The avoid loss of “charge”. Tube lengths longer than 4 ft. (1.2 m) should
MAC1 Volume Air Cell is non-corrosive and provides 1/4-20 stainless have provision for periodic air purging.
steel mounting studs.
Installation of the Volume Cell
Install the volume cell according to the level you wish the pump to start
and stop. Secured the volume cell with a substantial bracket which will
not allow the cell to be “floated”
The MACT1 Tubing Kit provides 4 ft. (1.2 m) flexible, non-corrosive
1/4 in. (6 mm) tubing (cut to fit). The kit includes necessary fittings to
attach tubing.
Both the MAC1 air cell and MACT1 tubing kit are available from
Murphy.
or tilted when the water level
DF755
rises. The DF755 should be
installed well above the highest
water level and in a position
that will allow access for
adjustment or repair.
Volume Cell Operation
As liquid rises around the volume cell, it compresses air inside the cell
and forces it up in the sensor line. As air pressure increases due to the
water level continuing to rise, sufficient pressure will be applied to acti-
vate the internal snap-switch, which in turn starts the pump. As the liq-
uid level is pumped down, pressure decreases and the above procedure
is reversed. The pump is stopped and held in a standby condition. An
air purge may be required in the sensor line. Consult factory.
Sensor Line
(MACT1 Tube Kit)
NOTE: Periodically operate pump
manually until water level reaches a
point approximately 1/2 in. (13 mm)
below bottom of the volume cell. This
Volume Cell
(MAC1)
will automatically re-charge the unit
and compensate for normal
absorption of air into water.
Small electric air pumps are
available to automatically
Choosing a Volume Cell
The volume cell should be constructed of material which will be unaf-
fected by the liquid being measured. For proper “pressure-to-level”
ratio, the minimum dimensions of the volume cell should be 6 in. (152
mm) inside diameter and 3 in. (76 mm) inside depth. The sensor line
can be of any diameter or material either flexible, or solid, as long as it
is of sufficient length to reach from the volume cell to the desired loca-
charge system at all times.
DF-94063N page 3 of 4
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TYPICAL WIRING
Starts at High Level, Stops at Low
Starts at Low Level, Stops at High
Start motor when predetermined low level is reached and stop when high
level is reached. Keeps tank level within selected limits. Motor starter
Start motor when predetermined high level is reached and stop when low level
is reached. Motor starter equipped with H.O.A.
HIGH
equipped with H.O.A.
HIGH
N.O.
N.O.
C
DF755
#1
DF755
#1
C
N.C.
N.O.
N.C.
N.O.
C
DF755
#2
DF755
#2
C
N.C.
N.C.
MOTOR
LOW
LOW
MOTOR
Single Magneto Shutdown
Dual Magneto Shutdown
Wiring of magneto to N.O. switch terminal will shut down engine at prede- Shutdown dual magneto engines using Murphy MS2120 Magnetic Switch.
termined high level, shown below. Wire to N.C. terminal to shutdown on Diagram below shows hookup for low level shutdown. Wiring changes and
low level.
mounting locations are necessary for high level shutdowns.
MAGNETO
Model MS2120
Magneto
N.O.
C
N.C.
6
1
2
3
4
5
N.O.
C
Magneto
N.C.
Jumper #2 & #5
SERVICE PARTS
DF755
DF757
Description
Part Number
15050081
15050082
80040607
15000122
80040605
15000123
15050083
15000313
15000121
Cover (aluminum)
Case (aluminum)
15050081
15050594
80040607
15000174
Cover (aluminum)
Case (aluminum)
Cover Screws (3), #6–32 x 5/16 round head
SPDT snap-switch and movement assembly/repair kit (5 amp)
Screws (3) for switch assembly to case, #6–32 x 1/4 round head
Diaphragm repair kit
Bottom Plate (1 NPT connection)
Bracket and movement repair kit
SPDT snap-switch and insulator repair kit (5 amp)
Cover Screw (3), #6–32 x 5/16 round head
SPDT snap-switch and bracket assembly/repair kit (5 amp)
Screws (2) for switch bracket and assembly to case (#6–32 x 1/4 round head) 80040605
Spring and piston assembly/repair kit
Diaphragm repair kit
Bottom Plate (1 NPT connection)
SPDT snap-switch and insulator repair kit (5 amp)
15000190
15000123
15050083
15000230
DF755EX
Cover (aluminum)
15050154
15050155
15050305
15000118
80040605
15000119
15000123
15050083
80040814
00000827
86060203
85030402
86060801
15000117
Case (aluminum)
Gasket
SPDT snap-switch and movement assembly/repair kit (5 amp)
Screws (2) for switch assembly to case, #6–32 x 1/4 round head
Actuator assembly/repair kit
Diaphragm repair kit
Bottom Plate (1 NPT connection)
Screw (1), #8–32 x 1/4 round head
Terminal cup washer
Plug 1/8 plastic pipe hex (DF755EX)
Connector, 1/4 tube x 1/8 pipe male (DF756)
Plug 1/2 NPT hex (brass)
SPDT snap-switch and insulator repair kit (5 amp)
CONTROL SYSTEMS & SERVICES DIVISION
P.O. Box 1819; Rosenberg, Texas 77471; USA
+1 281 633 4500 fax +1 281 633 4588
e-mail [email protected]
FRANK W. MURPHY, LTD.
Church Rd.; Laverstock, Salisbury SP1 1QZ; U.K.
+44 1722 410055 fax +44 1722 410088
e-mail [email protected]
MACQUARRIE CORPORATION
1620 Hume Highway
Campbellfield, Vic 3061; Australia
+61 3 9358 5555 fax +61 3 9358 5558
e-mail [email protected]
FW Murphy
P.O. Box 470248
MURPHY DE MEXICO, S.A. DE C.V.
Blvd. Antonio Rocha Cordero 300, Fracción del Aguaje
San Luis Potosí, S.L.P.; México 78384
+52 444 8206264 fax +52 444 8206336
Villahermosa Office +52 993 3162117
e-mail [email protected]
MURPHY SWITCH OF CALIFORNIA
41343 12th Street West
Palmdale, California 93551-1442; USA
+1 661 272 4700 fax +1 661 947 7570
e-mail [email protected]
Tulsa, Oklahoma 74147 USA
+1 918 317 4100
fax +1 918 317 4266
e-mail [email protected]
USA–ISO 9001:2000 FM 28221
UK–ISO 9001:2000 FM 29422
In order to consistently bring you the highest quality, full featured products, we reserve the right to change our specifications and designs at any time.
DF-94063N page 4 of 4
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