Murphy Switch DF Series User Manual

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  
FRANK W. MURPHY, LTD.  
Church Rd.; Laverstock, Salisbury SP1 1QZ; U.K.  
+44 1722 410055 fax +44 1722 410088  
MACQUARRIE CORPORATION  
1620 Hume Highway  
Campbellfield, Vic 3061; Australia  
+61 3 9358 5555 fax +61 3 9358 5558  
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  
MURPHY SWITCH OF CALIFORNIA  
41343 12th Street West  
Palmdale, California 93551-1442; USA  
+1 661 272 4700 fax +1 661 947 7570  
Tulsa, Oklahoma 74147 USA  
+1 918 317 4100  
fax +1 918 317 4266  
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  
Printed in U.S.A.  
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