Pentair Myers MRG20 Manual

NOTE! To the installer: Please make sure you provide this manual to the owner of the equipment or to the responsible
party who maintains the system.
MODEL MRG20
GRINDER PUMP
INSTALLATION AND SERVICE MANUAL
2 HP Grinder Pump for Residential Applications.
Part # 23833A665 | © 2012 Pentair Pump Group, Inc. | 11/08/12

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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

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SAFETY WARNINGS
nWARNING! Risk of electrical shock. Pumps are
supplied with a grounding conductor and grounding-
type attachment plug on the power cord. To reduce
the risk of electrical shock, be certain that it is
connected only to 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. When wiring this pump follow all local
electrical, safety codes and ordinances as well as most
recent National Electric Code (NEC-ANSI/NFPA).
The MRG20 grinder pumps have a GROUND WIRE
that is connected to a screw in the metal motor
housing. This wire goes to the receptacle or control
box which must be connected to follow all local
electrical, safety codes and ordinances as well as most
recent National Electric Code (NEC-ANSI/NFPA).
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.
DISMANTLING PUMP FOR
REPLACEMENT PARTS
Before dismantling pump for replacement parts, clean
pump thoroughly.
RUN
CAPACITOR
START
CAPACITOR
20 µF
370 V 324 µF - 389 µF
125 V
BROWN BLACK
PHASE
MAIN
ORANGE
YELLOW
BLUE
RED
LINE
LINE
WHITE
PROTECTOR
SENSATA TECHNOLOGIES TYPE 15HM2412
WIRING SCHEMATIC
2
3
5
1
4
6
WIRING SCHEMATIC – AO SMITH®WIRING DIAGRAM – MARATHON®
START
CAPACITOR
RUN
CAPACITOR

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Pump does not run or hum.
See A, B, C, D, E or F.
Pump runs but does not
deliver water.
See G, H, I, J, K or L.
Pump runs and pumps out sump
but does not stop.
See M.
Pump runs but delivers only
small amount of water.
See I, J, K, L or N.
Fuse blows or circuit breaker
trips when pump starts.
See K, L, N, O or P.
Motor runs for short time
then stops. Then after
short period starts again.
Indicates tripping overload
caused by symptom shown.
See K, L, N or P.
For any other symptoms
contact a Myers authorized
service facility.
A. Line circuit breaker may be off;
or fuse, if used, may be blown
or loose.
B. Water level in sump may be too
low. Run in more water.
C. Pump cord plug may not be
making contact in receptacle.
D. If pump is using the series cord
plug, the two plugs may not be
plugged tight together.
E. Float may be stuck. Be sure
float operates freely in basin.
Check tether length of switch.
F. If all symptoms check OK,
motor winding may be
open; take to service center
for repair.
G. Check valve may be installed
backward. Arrow on valve
points in direction of flow.
H. Discharge shut-off valve, if
used, may be closed.
I. Pump may be air locked. Start
and stop several times by
plugging and unplugging cord.
Check vent hole on pump case
for plugging.
J. Pump head may be too high.
Horizontal distance does
not affect pumping, except
loss due to friction.
K. Inlet holes in pump base may
be clogged. Remove pump
and clean out openings.
L. Impeller or volute openings may
be plugged or partially plugged.
Remove pump and clean.
Check tether length of switch.
M. Float is stuck in up position.
Be sure float operates freely
in basin.
N. Pump impeller may be
partially clogged causing
motor to run slow, resulting in
motor overload.
O. Fuse size or circuit breaker is
too small. Must be 20 amps.
P. Defective motor stator. Return
to Myers service center.
TROUBLESHOOTING GUIDE

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75
432
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6
MOTOR END PARTS
COMMON PARTS LIST
For use with product built with
AO Smith®motor.
Ref. No. Part No. Description
1 26433D002 CASE, VOLUTE
2 21584B000 FLANGE, W/SHREDDING RING
3 19099A012 SCREW, CAP 1/4" x 1" LONG., SST (3 REQ’D)
4 21583B000 RETAINER, IMPELLER, SST
5 07597A018 SCREW, FLAT HEAD, 1/4" x 3/4" LONG
6 25371B006 HANDLE
7 21582B000 IMPELLER, GRINDING
8 05013A039 SCREW, SET 1/4" x 3/8" LONG (2 REQ’D)
926434C010 IMPELLER, PUMP PLASTIC
26434C000 IMPELLER, CAST IRON (OPTIONAL)
10 26430D001 PLATE, SEAL/BEARING
11 05014A181 GASKET, TETRASEAL 7" x 6-3/4" x 1/8"
12 145890022 HOUSING, MOTOR
13 19100A012 SCREW, CAP, 5/16" x 1-1/4" LONG (8 REQ’D)
14 21576A010 SEAL, 7/8" SHAFT
15 27739D000 MOTOR, 2 HP, 230V, 1 PH
16 05022A092 PLUG, PIPE 1/4 NPT
17 05030A235 WASHER, SST, 3/32" THICK
18 05014A193 GASKET, RUBBER
19 05030A234 WASHER, SST, 1/32" THICK
20 25341A002 NUT, SOLID
21 25338B001 CORD, POWER
22 14595-020-1 SWITCH, FLOAT
– 152240021 RUN CAPACITOR
– 12141A018 START CAPACITOR

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MOTOR END PARTS
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5
7
4
8
9
10
11
12
14
15
16
17
22
21
23
20
19
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25
26
27
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30
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33
COMMON PARTS LIST
Ref. Part Number Description
1 26433D002 CASE, VOLUTE
2 21584B000 FLANGE, W/SHREDDING RING
3 19099A012 SCREW, CAP 1/4" x 1" LONG., SST (3 REQ’D)
4 21583B000 RETAINER, IMPELLER, SST
5 07597A018 SCREW, FLAT HEAD, 1/4" x 3/4" LONG
6 17190A004 CLAMP
7 21582B000 IMPELLER, GRINDING
8 05013A039 SCREW, SET 1/4" x 3/8" LONG (2 REQ’D)
926434C010 IMPELLER, PUMP PLASTIC MG200
26434C000 IMPELLER, CAST IRON (OPTIONAL) MG200
10 26430D001 PLATE, SEAL/BEARING
11 05014A181 GASKET, TETRASEAL 7" x 6-3/4" x 1/8"
12 145890021 HOUSING, MOTOR
13 19100A012 SCREW, CAP, 5/16" x 1-1/4" LONG (8 REQ’D)
14 21576A010 SEAL, 7/8" SHAFT
15 08565A018 BEARING, LOWER
16 N/A STATOR, W/SHELL, 2 HP, 230V, 1 PH
17 N/A ROTOR, W/SHAFT
18 24481A008 SWITCH, MECHANICAL
19 12141A015 CAPACITOR, START WITH RESISTOR
20 20333A001 CLIP, CAPACITOR
21 08565A013 BEARING, UPPER
22 12558A030 RING, RETAINING
23 19331A005 WASHER, SPRING FINGER
24 05022A009 PLUG, PIPE 1/4 NPT
25 05030A235 WASHER, SST, 3/32" THICK
26 05014A193 GASKET, RUBBER
27 05030A234 WASHER, SST, 1/32" THICK
28 25341A002 NUT, SOLID
29 25338B001 CORD, POWER
30 20333A004 CLIP, CAPACITOR
31 23838A010 CAPACITOR, RUN WITH RESISTOR
32 14595-020-1 SWITCH, FLOAT
33 25371B006K HANDLE
For use with product built with
Marathon®motor.
Entire motor can be replaced with 27739D000.

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1101 MYERS PARKWAY 490 PINEBUSH ROAD, UNIT #4
ASHLAND, OHIO, USA 44805 CAMBRIDGE, ONTARIO, CANADA N1T 0A5
419-289-1144 800-363-PUMP
WWW.FEMYERS.COM
Warranty Rev. 12/13
STANDARD LIMITED WARRANTY
Pentair Myers®warrants its products against defects in material and workmanship for a period of 12 months from the
date of shipment from Pentair Myers or 18 months from the manufacturing date, whichever occurs first – provided
that such products are used in compliance with the requirements of the Pentair Myers catalog and technical manuals
for use in pumping raw sewage, municipal wastewater or similar, abrasive-free, noncorrosive liquids.
During the warranty period and subject to the conditions set forth, Pentair Myers, at its discretion, will repair or
replace to the original user, the parts that prove defective in materials and workmanship. Pentair Myers reserves the
right to change or improve its products or any portions thereof without being obligated to provide such a change or
improvement for prior sold and/or shipped units.
Start-up reports and electrical schematics may be required to support warranty claims. Submit at the time of start-
up through the Pentair Myers website: http://forms.pentairliterature.com/startupform/startupform.asp?type=m.
Warranty is effective only if Pentair Myers authorized control panels are used. All seal fail and heat sensing devices
must be hooked up, functional and monitored or this warranty will be void. Pentair Myers will cover only the lower
seal and labor thereof for all dual seal pumps. Under no circumstance will Pentair Myers be responsible for the cost
of field labor, travel expenses, rented equipment, removal/reinstallation costs or freight expenses to and from the
factory or an authorized Pentair Myers service facility.
This limited warranty will not apply: (a) to defects or malfunctions resulting from failure to properly install, operate or
maintain the unit in accordance with the printed instructions provided; (b) to failures resulting from abuse, accident
or negligence; (c) to normal maintenance services and parts used in connection with such service; (d) to units that
are not installed in accordance with applicable local codes, ordinances and good trade practices; (e) if the unit is
moved from its original installation location; (f) if unit is used for purposes other than for what it is designed and
manufactured; (g) to any unit that has been repaired or altered by anyone other than Pentair Myers or an authorized
Pentair Myers service provider; (h) to any unit that has been repaired using non factory specified/OEM parts.
Warranty Exclusions: PENTAIR MYERS MAKES NO EXPRESS OR IMPLIED WARRANTIES THAT EXTEND BEYOND
THE DESCRIPTION ON THE FACE HEREOF. PENTAIR MYERS SPECIFICALLY DISCLAIMS THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR ANY PARTICULAR PURPOSE.
Liability Limitation: IN NO EVENT SHALL PENTAIR MYERS BE LIABLE OR RESPONSIBLE FOR CONSEQUENTIAL,
INCIDENTAL OR SPECIAL DAMAGES RESULTING FROM OR RELATED IN ANY MANNER TO ANY PENTAIR MYERS
PRODUCT OR PARTS THEREOF. PERSONAL INJURY AND/OR PROPERTY DAMAGE MAY RESULT FROM IMPROPER
INSTALLATION. PENTAIR MYERS DISCLAIMS ALL LIABILITY, INCLUDING LIABILITY UNDER THIS WARRANTY, FOR
IMPROPER INSTALLATION. PENTAIR MYERS RECOMMENDS INSTALLATION BY PROFESSIONALS.
Some states do not permit some or all of the above warranty limitations or the exclusion or limitation of incidental or
consequential damages and therefore such limitations may not apply to you. No warranties or representations at any
time made by any representatives of Pentair Myers shall vary or expand the provision hereof.