Gast 120R User manual

®
Registered Trademark/™ Trademark of Gast Manufacturing Inc. ©Copyright 2021 Gast Manufacturing Inc. All Rights Reserved.
www.gastmfg.com
ISO 9001 CERTIFIED
A UNIT OF IDEX CORPORATION
Part No. 70-7100 (Rev A)
Operation and Maintenance Manual
120R Rocking Piston
Oil-less Air Compressor

© 2021, Gast Manufacturing
We reserve the right to make any alterations which may be due to any technical improvements
Printed in the USA

Part No. 70-7100 (Rev. A)
Dear Customer:
Thank you for purchasing this Gast product. It is manufactured to the highest standards using quality
materials. Please follow all recommended maintenance, operational, and safety instructions and you will
receive years of trouble free service.
TABLE OF CONTENTS
Product Use, Criteria, and Purpose ......................................................................3
Mounting ..............................................................................................4
Plumbing ..............................................................................................4
Accessories. ...........................................................................................4
Motor Control ..........................................................................................4
Electrical Connection ...................................................................................4
Extension Cords ........................................................................................4
Operation ..............................................................................................5
Start Up................................................................................................5
Maintenance ...........................................................................................6
Shut Down Procedures .................................................................................6
Service Kit Installation ..................................................................................6
Parts and Ordering Information..........................................................................8
Troubleshooting Chart ..................................................................................9
Warranty Policy .......................................................................................10
WARNING
PLEASE READ THIS MANUAL COMPLETELY BEFORE INSTALLING AND USING THIS PRODUCT.
SAVE THIS MANUAL FOR FUTURE REFERENCE AND KEEP IN THE VICINITY OF THE PRODUCT.

© 2021, Gast Manufacturing
We reserve the right to make any alterations which may be due to any technical improvements
Printed in the USA

Part No. 70-7100 (Rev. A)
PRODUCT USE CRITERIA, AND PURPOSE
• Pump only clean, dry air.
• Operate at 32°F to 104°F (0°C to 40°C).
• Protect unit from dirt and moisture.
• Do not pump flammable or explosive gases or use in an
atmosphere that contains such gases.
• Protect all surrounding items from exhaust air. This exhaust
air can become very hot.
• Corrosive gases and particulate material will damage unit.
Water vapor, oil-based contaminants, or other liquids must
be filtered out.
• Consult your Gast Distributor/Representative before using at
high altitudes.
• This pump is oil-less and requires NO lubrication.
• Compressor surfaces can become hot during operation. Do
not touch.
Your safety and the safety of others is extremely important.
We have provided many important safety messages in this
manual and on your product. Always read and obey safety
messages.
This is the safety alert symbol. This symbol alerts
you to hazards that can kill or hurt you and others.
The safety alert symbol and the words “DANGER”
and “WARNING” will precede all safety messages.
These words mean:
mDANGER
You will be killed or seriously injured if you don’t follow in-
structions.
mWARNING
You can be killed or seriously injured if you don’t follow
instructions.
All safety messages will identify the hazard, tell you how to
reduce the chance of injury, and tell you what can happen if
the safety instructions are not followed.
INSTALLATION
WARNING
Electrical Shock Hazard
Disconnect electrical power at the circuit breaker or fuse
box before installing this product.
Install this product where it will not encounter water or
other liquids.
Install this product where it will be weather protected.
Electrically ground this product.
Failure to follow these instructions can result in death, fire,
or electrical shock.
Correct installation is your responsibility. Make sure you have
the proper installation conditions and that installation clearances
do not block air flow.
WARNING
Blocking air flow over the product in any way can cause
the product to overheat.

© 2021, Gast Manufacturing
We reserve the right to make any alterations which may be due to any technical improvements
Printed in the USA

Part No. 70-7100 (Rev. A)
MOUNTING
This product can be installed on a horizontal surface. Mounting
the product to a stable, rigid operating surface and using
supplied shock mounts will reduce noise and vibration. This
product is provided with vibration mounts and adjustable
mounting foot. To adjust mounting pattern, loosen vibration
mounts to and slide mounting bracket to desired location. Secure
vibration mounts to body and mounting bracket before attaching
compressor to application.
Optional mounting orientation is available. Consult Factory or
Distributor for details.
PLUMBING
Remove plugs from the IN and OUT ports. Connect with pipe
and fittings that are the same size or larger than the product’s
threaded ports. Be sure to connect the intake and exhaust
plumbing to the correct inlet and outlet ports. Ports will not
support plumbing.
ACCESSORIES
The product’s external intake and exhaust muffler will provide
adequate filtration in most applications. Check filters periodically
and replace when necessary. Consult your Gast Distributor/
Representative for additional filter recommendations.
Install relief valves and gauges at inlet or outlet or both, to
monitor performance. Check valves may be required to prevent
back streaming through the pump.
MOTOR CONTROL
It is your responsibility to contact a qualified electrician
and assure that the electrical installation is adequate and in
conformance with all national and local codes and ordinances.
The metal capacitor must be grounded.
Determine the correct overload setting required to protect the
motor (see motor starter manufacturer’s recommendations).
Select fuses, motor protective switches or thermal protective
switches to provide protection. Fuses act as short circuit
protection for the motor, not as protection against overload.
Incoming line fuses must be able to withstand the motor’s
starting current. Motor starters with thermal magnetic overload
or circuit breakers protect motor from overload or reduced
voltage conditions.
The wiring diagram supplied with the product provides required
electrical information. Check that power source is correct to
properly operate the dual-voltage motors.
WARNING
Electrical Shock Hazard
This product must be properly grounded.
Do not modify the plug provided. If it will not fit the outlet,
have the proper outlet installed by a qualified electrician.
If repair or replacement of the cord or plug is necessary,
do not connect the grounding wire to either flat blade
terminal. The wire with insulation that is green or
green with yellow stripes is the grounding wire.
Check the condition of the power supply wiring.
Do not permanently connect this product to wiring that
is not in good condition or is inadequate for the
requirements of this product.
Failure to follow these instructions can result in death, fire,
or electrical shock.
grounding pin
220/240-volt grounded
connectors will differ in shape.
Model with a Power Supply Cord
This product must be grounded. For 220/240-volt circuits
connect power supply cord grounding plug to a matching
grounded outlet. Do not use an adapter. (See above diagram.)
In the event of an electrical short circuit, grounding reduces the
risk of electric shock by providing an escape wire for the electric
current. This product may be equipped with a power supply cord
having a grounding wire with an appropriate grounding plug.
The plug must be plugged into an outlet that is properly installed
and grounded in accordance with all local codes and ordinances
Check with a qualified electrician or serviceman if the
grounding instructions are not completely understood, or if you
are not sure whether the product is properly grounded. Do not
modify the plug provided. If it will not fit the outlet, have the
proper outlet installed by a qualified electrician.

© 2021, Gast Manufacturing
We reserve the right to make any alterations which may be due to any technical improvements
Printed in the USA

Part No. 70-7100 (Rev. A)
Model that is Permanently Wired
This product must be connected to a grounded, metallic,
permanent wiring system, or an equipment grounding terminal or
lead on the product.
Power supply wiring must conform to all required safety codes
and be installed by a qualified person. Check that supply voltage
agrees with that listed on product nameplate.
Extension Cords
Use only a 3-wire extension cord that has a 3-blade grounding
plug. Connect extension cord plug to a matching 3-slot
receptacle. Do not use an adapter. Make sure your extension cord
is in good condition. Check that the gage wire of the extension
cord is the correct size wire to carry the current this product will
draw.
An undersized cord is a potential fire hazard and will cause a
drop in line voltage resulting in loss of power causing the product
to overheat. The following table indicates the correct size cord
for length required and the ampere rating listed on the product
nameplate. If in doubt, use the next heavier gage cord. The
smaller the gage number, the heavier the wire gage.
Minimum gage for extension cords
Amps Volts Length of cord in feet
240v 50 100 200 300 400 500 600 800 1000
0-2 18 18 18 16 16 14 14 12 12
2-3 18 18 16 14 14 12 12 10 10
3-4 18 18 16 14 12 12 10 10 8
4-5 18 18 14 12 12 10 10 8 8
5-6 18 16 14 12 10 10 8 8 8
6-8 18 16 12 10 10 8 6 6 6
8-10 18 14 12 10 8 8 6 6 4
10-12 16 14 10 8 8 6 6 4 4
12-14 16 12 10 8 6 6 6 4 2
14-16 16 12 10 8 6 6 4 4 2
16-18 14 12 8 8 6 4 4 2 2
18-20 14 12 8 6 6 4 4 2 2
OPERATION
WARNING
Injury Hazard
Install proper safety guards as needed.
Keep fingers and objects away from openings and
rotating parts.
When provided, motor terminal covers must be in place
for safe operation.
Product surfaces become very hot during operation,
allow product surfaces to cool before handling.
Air stream from the product may contain solid or liquid
material that can result in eye or skin damage, wear proper
eye protection.
Wear hearing protection. Sound level from motor may
exceed 70 dBA.
Failure to follow these instructions can result in burns,
eye injury, or other serious injury.
It is your responsibility to operate this product at recommended
pressures or vacuum duties and room ambient temperatures. Do
not start against a vacuum or pressure load.
Start Up
If motor fails to start or slows down significantly under load, shut
off and disconnect from power supply. Check that the voltage
is correct for motor and that motor is turning in the proper
direction. Check the plug, cord and switch for damage. If so
equipped, the thermal protection switch has tripped, the motor
can restart after cooling.

© 2021, Gast Manufacturing
We reserve the right to make any alterations which may be due to any technical improvements
Printed in the USA

Part No. 70-7100 (Rev. A)
MAINTENANCE
WARNING
Electrical Shock Hazard
Disconnect electrical power supply before performing
maintenance on this product.
If product is hard-wired into system, disconnect electrical
power at the circuit breaker or fuse box before
performing maintenance on this product.
Failure to follow these instructions can result in death, fire,
or electrical shock.
WARNING
Injury Hazard
Product surfaces become very hot during operation,
allow product surfaces to cool before handling.
Air stream from the product may contain solid or liquid
material that can result in eye or skin damage, wear proper
eye protection.
Clean this product in a well-ventilated area.
Failure to follow these instructions can result in burns,
eye injury, or other serious injury.
It is your responsibility to:
• Regularly inspect and make necessary repairs to product
in order to maintain proper operation.
• Make sure that pressure is released from product before
starting maintenance.
Check intake and exhaust filters after first 500 hours of
operation. Clean filters and determine how frequently filters
should be checked during future operation. This one procedure
will help to assure the product’s performance and service life.
1. Disconnect electrical power supply to unit.
2. Vent all air lines.
3. Remove filter cover.
4. Check filter element. Replace filter if element is covered
with contamination or shows signs of increasing differential
pressure.
5. Reinstall filter element and filter cover.
Check that all external accessories such as relief valves and
gauges are attached to cover and are not damaged before re-
operating product.
SHUT DOWN
It is your responsibility to follow proper shutdown procedures
to prevent product damage. NEVER ADD OIL TO THIS OIL-LESS
PUMP.
Proper shutdown procedures must be followed to prevent
pump damage. Failure to do so may result in premature pump
failure. Gast Manufacturing Rocking Piston Oil-Less Pumps are
constructed of ferrous metals or aluminum which are subject
to rust and corrosion when pumping condensable vapors such
as water. Follow the steps below to assure correct storage and
shutdown between operating periods.
1. Disconnect plumbing.
2. Operate product for at least five minutes without plumbing.
3. Run at maximum vacuum for 10 to 15 minutes.
4. Repeat step 2.
5. Disconnect power supply.
6. Plug open ports to prevent dirt or other contaminants from
entering product.
SERVICE KIT INSTALLATION
WARNING
Electrical Shock Hazard
Disconnect electrical power supply before performing
maintenance on this product.
If product is hard-wired into system, disconnect electrical
power at the circuit breaker or fuse box before
performing maintenance on this product.
Vent all air lines to release pressure or vacuum.
Failure to follow these instructions can result in death, fire,
or electrical shock.
Gast will NOT guarantee field-rebuilt product performance.
For performance guarantee, the product must be returned to a
Gast Authorized Service Facility.

© 2021, Gast Manufacturing
We reserve the right to make any alterations which may be due to any technical improvements
Printed in the USA

Part No. 70-7100 (Rev. A)
Gast offers the following Service Kits for the 120R compressor.
Description Kit Number Service Interval
120R Preventative Maintenance Kit K1027 1000 hours or one year
120R Service Kit K1028 6000 hours or five years
120R Capacitor Replacement Kit K1029 Five years
120R Capacitor Cover K1030 As needed
120R Spare Parts Kits K1031 As needed
120R Side Mount Bracket Kit K1032 As needed
Reducing Bushing 3/8 to 1/4 UK6502 As needed
1. Disconnect electrical power to pump.
2. Disconnect air supply and vent all air lines to release
pressure or vacuum.
3. Consult individual kit instruction to install components
Check that all external accessories such as relief valves and
gauges are not damaged before operating product.
If pump still does not produce proper vacuum or pressure, send
unit to a Gast Authorized Service Facility for repair.

© 2021, Gast Manufacturing
We reserve the right to make any alterations which may be due to any technical improvements
Printed in the USA

Part No. 70-7100 (Rev. A)
EXPLODED PRODUCT VIEW
15
9
11
18
8
7
13
3
12
1
4
14
2
17
19
10
16
5
6
20
ITEM NO.
PART NUMBER
DESCRIPTION QTY.
1
N800NX
MOTOR
1
STATOR (N800NX)
STATOR (N800NX)
1
ROTOR (N800NX)
ROTOR (N800NX)
1
2
AP808B
BODY, LARGE BRG, THRU
4
3
AP808A
BODY, LARGE BRG, TAPPED
1
4
BRG1501
BRG 6006 FCST
2
5
VPA1500
VALVE PLATE ASSEMBLY
1
VPL1500
VALVE PLATE
1
5485150
LEAF VALVE
2
6392165
PHCS M5 X 0.8 X 8.0 TORX TAPTITE
2
VRP1500
VALVE RETAINER
1
5485152
LIMITER
1
6
VPA1501
VALVE PLATE ASSEMBLY
1
VPL1500
VALVE PLATE
1
5485150
LEAF VALVE
2
6392165
PHCS M5 X 0.8 X 8.0 TORX TAPTITE
2
VRP1500
VALVE RETAINER
1
5485152
LIMITER
1
7
BC104
HEX NUT - 1/4-20
4
8
FAC1500 FAN COVER
2
9
SCR1500 SHCS, #10-32 X 2 3/4" LONG
8
10
ORG1500
O-RING
2
11
HDC1500HEAD
1
12
FMB1500
FOOT MOUNTING BRACKET
2
13
AT825
SHOCK_MOUNT (M6 x 1/4-20)
4
14
BB648 HHCS_1/4-20 X 3/8" LONG
4
15
BA504
PIPE PLUG, 3/8 NPT
2
16
CRA1500
CONNECTING ROD SUB-
ASSEMBLY
2
CNR1500G
CONNECTING ROD
1
BRG1500
BRG 6006 FCST
1
ECC1500G
ECCENTRIC
1
6289560
CUP
1
6392350
FHCS M8 X 1.25 X 25.0 UH FZB
TORX
1
CRP1500
RETAINER PLATE
1
CYL1500 CYLINDER, 80mm (3.15)
1
17
FAN1500
FAN, 8-BLADE
1
18
FAN1501
FAN, 8-BLADE
1
19
ORG1501
O-RING
2
20
FIL1500 FILTER
1
Capacitor NOT shown

© 2021, Gast Manufacturing
We reserve the right to make any alterations which may be due to any technical improvements
Printed in the USA

Part No. 70-7100 (Rev. A)
TROUBLESHOOTING CHART
SERVICE AND MAINTENANCE CHART
Date Problem Technician Notes
Low
Pressure
High
Pressure
Low
Vacuum
Excessive
Noise
Over-
heating
Won’t
Start Possible reason
ÒDirty filter
ÒDirty muffler
Ò Ò Dirty valves – clean or replace
Ò Ò Bent/damaged valves – replace
Ò Ò Ò Damaged/worn cup – replace
Ò Ò Ò Leaky hose
Ò Ò Leaky check valve
Ò Ò Ò Ò Plugged vacuum or pressure line
Ò Ò Low voltage
ÒLeaky relief valve
Ò Ò Motor not wired correctly – check
wiring diagram/line voltage

WARRANTY
Gast finished products, when properly installed and operated under normal conditions of use, are warranted by Gast to be free from defects in material
and workmanship for a period of twelve (12) months from the date of purchase from Gast or an authorized Gast Representative or Distributor. In order to
obtain performance under this warranty, the buyer must promptly (in no event later than thirty (30) days after discovery of the defect) give written notice
of the defect to Gast Manufacturing Incorporated, PO Box 97, Benton Harbor Michigan USA 49023-0097 or an authorized Service Center (unless specif-
ically agreed upon in writing signed by both parties or specified in writing as part of a Gast OEM Quotation). Buyer is responsible for freight charges both
to and from Gast in all cases.
This warranty does not apply to electric motors, electrical controls, and gasoline engines not supplied by Gast. Gast’s warranties also do not extend to
any goods or parts which have been subjected to misuse, lack of maintenance,neglect, damage by accident or transit damage.
THIS EXPRESS WARRANTY EXCLUDES ALL OTHER WARRANTIES OR REPRESENTATIONS EXPRESSED OR IMPLIED BY ANY LITERATURE, DATA, OR
PERSON. GAST’S MAXIMUM LIABILITY UNDER THIS EXCLUSIVE REMEDY SHALL NEVER EXCEED THE COST OF THE SUBJECT PRODUCT AND GAST
RESERVES THE RIGHT, AT ITS SOLE DISCRETION, TO REFUND THE PURCHASE PRICE IN LIEU OF REPAIR OR REPLACEMENT.
GAST WILL NOT BE RESPONSIBLE OR LIABLE FOR INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,however arising, including but not limited
to those for use of any products, loss of time, inconvenience, lost profit, labor charges, or other incidental or consequential damages with respect to
persons, business, or property, whether as a result of breach of warranty, negligence or otherwise. Notwithstanding any other provision of this warran-
ty, BUYER’S REMEDY AGAINST GAST FOR GOODS SUPPLIED OR FOR NON-DELIVERED GOODS OR FAILURE TO FURNISH GOODS, WHETHER OR NOT
BASED ON NEGLIGENCE, STRICT LIABILITY OR BREACH OF EXPRESS OR IMPLIED WARRANTY IS LIMITED SOLELY, AT GAST’S OPTION, TO REPLACE-
MENT OF OR CURE OF SUCH NONCONFORMING OR NON-DELIVERED GOODS OR RETURN OF THE PURCHASE PRICE FOR SUCH GOODS AND IN NO
EVENTS HALL EXCEED THE PRICE OR CHARGE FOR SUCH GOODS. GAST EXPRESSLY DISCLAIMS ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR USE OR PURPOSE WITH RESPECT TO THE GOODS SOLD. THERE ARE NO WARRANTIES WHICH EXTEND BEYOND THE DESCRIP-
TIONS SET FORTH IN THIS WARRANTY, notwithstanding any knowledge of Gast regarding the use or uses intended to be made of goods, proposed
changes or additions to goods, or any assistance or suggestions that may have been made by Gast personnel.
Unauthorized extensions of warranties by the customer shall remain the customer’s responsibility.
CUSTOMER IS RESPONSIBLE FOR DETERMINING THE SUITABILITY OF GAST PRODUCTS FOR CUSTOMER’S USE OR RESALE, OR FOR INCORPORATING
THEM INTO OBJECTS OR APPLICATIONS WHICH CUSTOMER DESIGNS, ASSEMBLES, CONSTRUCTS OR MANUFACTURES.
This warranty can be modified only by authorized Gast personnel by signing a specific, written description of any modifications.
®
Registered Trademark/™ Trademark of Gast Manufacturing Inc. ©Copyright 2021 Gast Manufacturing Inc. All Rights Reserved.
www.gastmfg.com
ISO 9001 CERTIFIED
A UNIT OF IDEX CORPORATION
Gast Manufacturing
2300 M-139 Highway
Benton Harbor, MI 49023
Ph: 269-926-6171
Fax: [phone]
www.gastmfg.com
Gast Group Limited
c/o IDEX Trading (Shanghai) Co., LTD
Room 3502-3505
No. 1027 Chang Ning Road,
Zhaofeng Plaza
Shanghai, China 200050
Phone [phone]
Fax [phone]
Gast Group Ltd.
Unit 11, The I O Centre
Nash Road
Redditch, B98 7AS
United Kingdom
Phone [phone]
Fax [phone]
Part No. 70-7100 (Rev. A)