
23833A665 11/08/12 2
USAGE
The MRG20 is a submersible wastewater grinder
pump designed specifically for individual residential
applications. The pumps are to be used for domestic
sewage only and are not to be used for pumping
commercial or industrial sewage such as motels,
schools, apartments, factories, etc. THIS PUMP IS
NOT FOR USE IN HAZARDOUS LOCATIONS!
INSPECTING PUMP
Before making any piping or electrical connections,
check the pump for shipping damage or cracks.
Using a flat screwdriver placed in the slot on the
shaft end, turn shaft and impellers to be sure they are
free. DO NOT TURN IMPELLER WITH FINGERS AS
EDGES ARE SHARP.
POWER SUPPLY
The MRG20 grinder pump should be connected only
to a 230 volt, single phase, 60 Hz power source.
The pump will draw approximately 9.1 amperes at
minimum flow and 15.0 full load amperes. The pump
must be connected to a grounded power socket. DO
NOT cut off the ground pin from the power cord plug.
POWER CORD
A power cord is attached to the grinder pump via
three insulated quick-disconnect terminals.
The power cord should be replaced if it has
been damaged in any way or the cord jacket
has become brittle.
MOTOR TYPE
The MRG20 grinder pump contains a 3/4 frame, 2
HP, single phase, 60 Hz, 3450 RPM, capacitor start
- capacitor run motor with Class F insulation and
built-in on-winding overload protection. Motor has
upper and lower ball bearings and is oil-cooled and
lubricated.
nCAUTION!
THE MRG20 GRINDER PUMP SHOULD NEVER BE
WORKED ON WITHOUT FIRST DISCONNECTING
THE POWER CORD.
OIL TYPE
The motor housing contains dielectric transformer oil
to provide good heat transfer and lubrication of ball
bearings; no other lubrication is required. Oil level
may be checked by removing the nut and washers
from the top of the motor housing. The oil level
should be 3-7/8" from the boss with pump setting
vertically. Do not overfill with oil. Only dielectric
transformer oil obtained from a Myers authorized
service center should be used.
PUMP SWITCH INSTALLATION
INSTRUCTIONS
Mounting the Switch
1. Determine pumping range for installation. Do not
tether less than 3-1/2" from pipe.
2. Tighten strap around discharge pipe,
keeping switch cable between strap and pipe
to prevent slippage.
3. Space small ties at least 1" apart. To readjust ties,
press small tie tabs down.
4. To lock releasable tab, run remaining
strap between tab and head. Tuck strap
back through head.
Piggyback Plug Install
nElectrical outlet must not be located in
pump chamber.
nElectrical outlet voltage, piggyback plug voltage,
and pump voltage must match.
1. Follow steps 1 through 4 of “Mounting the Switch.”
2. Insert switch’s piggyback plug into outlet.
3. Plug pump into piggyback plug.
4. Check installation. Allow system to cycle to ensure
proper operation.
Direct Wire Install
1. Follow steps 1 through 4 of “Mounting the Switch”
2. Further wiring of switch should be done by
qualified professionals only.
3. Check installation. Allow system to cycle to ensure
proper operation.
liquid-tight
connector
230V
pump
230V
power
source
junction
box
black
white
L1
L2
G
G
L1
L2
G
230 VAC
In 230 VAC pump installations, one side of
the line going to the pump is always HOT.
This condition exists if the switch is on or
off. Install double pole disconnect on all
230 VAC pump circuits.
n WARNING