Myers MW50 Installation Manual

MW50 SERIES

SUBMERSIBLE SEWAGE PUMP

INSTALLATION AND SERVICE MANUAL

Automatic and manual models. Single phase power only — 115 or 230 volt.

NOTE! To the installer: Please make sure you provide this manual to the owner of the equip ment or to the responsible
party who maintains the system.

Part # 23833A275 | © 2012 Pentair Pump Group, Inc. | 11/08/12

DESCRIPTION AND APPLICATION

General: The MW50 is available in 115 volt or 230

volt, single phase, 1/2 HP motors. All units are single
seal only, available in automatic or manual with either
10' or 20' power cords. All power cords have either
115 volt or 230 volt grounded plugs.

These pumps are NOT for use in swimming pools or
fountains.

The pump has a mercury-free, 115 or 230 volt
mechanical piggyback float switch, available in 10'
and 20' lengths. The switch is provided with a cable
tie to be mounted to the discharge pipe and tethered
a minimum of 4". Plug the switch cord plug into a
proper voltage, properly grounded outlet. Plug the
power cord into the back of the switch cord and tape
the cords to the discharge pipe every 12".

MOTOR TYPE

MW50: The MW50 Series pumps are designed for

use in residential sewage applications. These units
are designed for handling raw sewage discharged for
residential and light commercial developments.

Impellers are enclosed two-vane type to handle
2" spherical solids and are made of engineered
thermoplastic or bronze. The discharge pipe size is 2"
NPT for attachment to almost all sewage applications.

AIR LOCKING

A sump pump is said to be air locked if water traps air
in the pump and it cannot get out, thus preventing the
pump from operating.

The MW50 pumps have a 1/16" air vent hole in the
impeller chamber to let out trapped air. If this hole
becomes plugged, the pump may air lock. As a
secondary precaution a 1/8" hole should be drilled
in the discharge pipe below the check valve. The
check valve should be 12 to 18 inches above pump
discharge. Do not put check valve directly into pump
discharge opening.

The motors used are pressed into the cast iron
housing and surrounded by dielectric oil for the
greatest heat dissipation. A permanent split capacitor,
1/2 HP, 1625 RPM motor is used. The unit has
Class A motor insulation, and is available in single
phase, 115 or 230 volt with overload protection and
uses a lower ball bearing - upper sleeve bearing. The
pump has no starting switches and does not require
a control panel for simplex installation.

SAFETY WARNINGS

WARNING: Risk of electric shock. Pumps are
supplied with a grounding conductor and
grounding-type attachment plug on the power
cord. To reduce the risk of electric shock, be
certain that it is connected only to a properly
grounded, grounding-type receptacle. DO NOT
cut off ground pin or use an adapter fitting. DO
NOT use an extension cord with this pump. Entire
plug may be cut off if a control panel is used.

When wiring this pump, follow all local electrical and
safety codes and ordinances as well as the most
recent National Electric Code (NEC-ANSI/NFPA 70).

LEVEL CONTROLS

All pumps must use sealed level control switches for
automatic operation. All automatic pumps have built­in level control float switches. The power cord has a
GROUND PIN that plugs into a grounded receptacle.
The grounded receptacle cannot be used in the wet
sump or basin due to DANGER of current leakage.

Manual pumps can be made automatic with MLC or
MFLC controls with a series plug. Plug the MLC or
MFLC witch cord series plug into a proper voltage
GROUNDED RECEPTACLE. Then plug the pump
cord plug into the back of the switch cord series plug.
NOTE: The float control must be tethered a minimum
4" to pump or discharge pipe. Control must float free
from pump and basin wall.

On all duplex units or simplex installations with
additional options like high water alarm, the power
cord plug must be cut off and wired into a control
panel or into a sealed junction box if used in wet
sump or basin. The AWS-1 control also acts as a
sealed junction box for connecting power cord to
pump cord.

23833A275 11/08/12

All pumps have a GROUND WIRE that is connected to
the motor. This wire goes to the receptacle or control
panel which must be connected to a good outside
GROUND such as a metal water pipe or GROUND
STAKE DRIVEN AT LEAST 8 feet into the ground.

CALIFORNIA PROPOSITION 65 WARNING:

This product and related
accessories contain chemicals known to the
State of California to cause cancer, birth
defects or other reproductive harm.

INSTALLATION

WARNING: Basin or tank must be vented in
accordance with local plumbing codes. These
pumps are not designed for and CANNOT be
installed in locations classified as hazardous in
accordance with the National Electric Code ANSI/
NFPA 70.

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CAUTION: Never enter pump chamber after
sewage or effluent has been in basin. Sewage
water can give off methane, hydrogen sulfide, and
other gases which are highly poisonous. For this
reason, Myers recommends installing effluent
pumps with a quick removal system. The quick
removal system may be a union or Cam-lok®
coupling if the pipe or discharge hose is within
reach from the surface, or a rail system type quick
disconnect on deeper installations.

The dosing tank or pumping chamber must be
constructed of corrosion resistant materials and must
be capable of withstanding all anticipated internal
and external loads. It also must not allow infiltration
or exfiltration. The tank must have provisions for
antibuoyancy. Access holes or covers must be
adequate size and be accessible from the surface to
allow for installation and maintenance of the system.
Access covers must be lockable or heavy enough
to prevent easy access by unauthorized personnel.
The pumping chamber holding capacity should be
selected to allow for emergency conditions.

The discharge pipe must be the same size as the
pump discharge, 2" or larger. In order to ensure
sufficient fluid velocity to prevent any residual
solids from collecting in the discharge pipe, it is
recommended that a minimum flow of 2' per second
be maintained (21 GPM through 2" pipe and 46 GPM
through 3" pipe). It is recommended that PVC or

equal pipe is used for corrosion resistance. A full
flow (ball or gate) shut-off valve must be installed to
prevent back flow of effluent if the pump must be
removed for service. A check valve must be installed
on pressure sewer systems and on other systems
where conditions allow to prevent back flow and to
reduce wear on the pump system.

A high water alarm must be installed on a separate
circuit from the pump circuit. The alarm should have
the ability to be tested for proper operation.

TO REPLACE AUTOMATIC
CONTROL FLOAT

1. Use a wrench to loosen and remove thermoplastic

nut from the cap socket. Use your fingers to
pull and wiggle the cord end connector from the
socket.

2. Align the half circle notch on the cord end

connector with the half circle key in the socket.
Press the connector into the socket all the way.

3. Slide the thermoplastic washer onto the top of the

cord end connector.

4. Screw the thermoplastic nut into the socket.

Tighten the nut snugly, but do not overtighten.
The nut may be tightened a little more after the
connector has set over a period of time.

5. Tether float approximately 3-5/8".

CONDITION

Pump does not run or start when
water is up in tank.

Pump runs but does not deliver flow.

TROUBLE CHECK LIST

PROBABLE CAUSE

1. Check for blown fuse or tripped circuit breaker.

2. Check for defective level switch.

3. Where control panel is used, be sure H-O-A switch is in
the AUTO position. If it does not run, turn switch to the
HAND position and if the pump runs then the trouble is in
the automatic electrical system. Have ELECTRICIAN make
electrical checks.

4. Check for burned-out motor. Occasionally lightning can
damage a motor even with lightning protection.

5. Where plug-in cords are used, be sure contact blades are
clean and making good contact. DO NOT USE PLUG-IN
CORDS INSIDE A SUMP OR WET WELL.

6. Level control ball or weight may be stuck on side of basin.
Be sure it floats freely.

1. Check for air lock. Start and stop pump several times. If this
does not help it may be necessary to loosen a union in the
discharge line to relieve air lock.

2. Check valve may be installed backward. Check flow arrow
on valve body. Check shut-off valve. It may be closed.

3. Check vertical elevation. It may be higher than pump can
develop.

4. Pump inlet may be plugged. Remove pump to check.

CAUTION: ALWAYS UNPLUG POWER CORDS OR TURN OFF ALL MAIN AND BRANCH CIRCUIT BREAKERS
BEFORE DOING ANY WORK ON THE PUMP. If control panel is remote from pump, disconnect lead wires to
motor so that no one can turn the circuit breaker back on.

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23833A275 11/08/12