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Stationary
Air Compressor
Manual
For US General Models
3848 93274 90836
US660V US560V US7580V
For questions concerning this air compressor,
please call: 1-866-869-3114.
Printed In USARev. 0110
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TABLE OF CONTENTS
PAGE
1 Safety Guidelines - Definitions
Before Using the Air Compressor
2 When Installing or Moving the Compressor
Before Each Use
3 Follow Safety Precautions for Electrical Connection
Plan Ahead to Protect Your Eyes, Hands, Face & Ears
When Operating
4 Spraying Precautions
Perform These Maintenance Operations
5 Warning Labels
Glossary
6 Wiring
Starting the Compressor
7-8 Troubleshooting
9 Parts
10 Warranty Statement
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SAFETY GUIDELINES - DEFINITIONS
Safety is a combination of common sense, staying alert and knowing how your compressor works.
Read this manual to understand this compressor.
DANGER
means if safety information is not followed someone will be seriously injured or killed
WARNING
means if safety information is not followed someone could be seriously injured or killed
CAUTION
means if safety information is not followed someone may be seriously injured or killed
IMPORTANT SAFETY INSTRUCTIONS
Save these instructions
Improper operation or maintenance of this product could result in serious injury and property
damage. Read and understand all warnings and operation instructions before using this compressor.
Before using the air compressor
Things you should know Inspect your work area
Air compressors are utilized in a variety of air
system applications. Because air compressors
and other components (hoses, connectors, air
tools, spray guns, etc.) make up a high pressure
pumping system, the following safety precautions should be observed at all times.
Only persons familiar with these rules of
safe operation should use the air
compressor.
1. Read the instruction manual carefully before
attempting to assemble, disassemble or
operate your system. Be thoroughly familiar
with the controls and the proper use of the
equipment.
2. Review and understand all safety instructions
and operating procedures in this manual.
1. Keep work area clean.
2. Cluttered areas and benches invite accidents.
Floors must not be slippery from wax or dust.
Inspect your compressor
1. To reduce the risk of injury from accidental
starting, turn switch off and disconnect the
power before checking it.
2. If any part is missing, bent or broken in any
way, or any electrical part does not work prop erly, keep the compressor off and disconnected.
3. Check hoses for weak or worn condition
before each use, making certain all connections
are secure. Do Not use if defect is found.
WARNING
3. Review the maintenance methods for this
compressor (See “Maintaining Your
Compressor” section).
Do not operate compressor if damaged during
shipping, handling or use. Damage may result
in bursting and cause injury or property damage.
DANGER
This compressor is Not designed for and should
not be used in breathing air applications.
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When installing or moving the compressor
WARNING
This compressor is extremely top heavy. The
compressor must be bolted to the floor with
vibration pads before operating to prevent
equipment damage, injury or death. Do Not
tighten bolts completely as this may
cause stress to the tank welds.
To reduce the risk of a dangerous
environment
1. Keep work area well lit.
2. Operate compressor in a well-ventilated
area free from flammable liquids and vapors.
3. Operate compressor in a ventilated area so
that compressor may be properly cooled and
the surrounding air temperature will not be
more than 100°F.
4. Never use a compressor in a wet
environment.
6. A minimum clearance of 18 inches between
the compressor and a wall is required
because objects could obstruct airflow.
7. The compressor should be located where it can
be directly wired to a circuit breaker. The
compressor should be wired by a qualified
electrician.
8. Never store flammable liquids or gases in
the vicinity of an operating compressor.
9. Do Not locate the compressor air inlet near
steam, paint spray, sandblasting areas or
any other source of contamination. The
debris could damage the motor and pump.
WARNING
Never use plastic (PVC) pipe for compressed
air. Serious injury or death could result.
CAUTION
5. Protect material lines and air lines from
damage or puncture. Keep hose and
wires away from sharp objects, chemical
spills, oil, solvents and wet floors.
WARNING
Do Not secure compressor with toggle bolts
into drywall. Drywall sheeting or plaster will not
support the weight of the compressor.
Never use the shipping skid for mounting the
compressor.
NOTICE
This compressor is not intended for outdoor
installation.
WARNING
Never install a shut off valve between the compressor pump and tank. Personal injury and/or
equipment damage could occur.
Note: Tank Outlet Size: 1/2” NPT for Stock# 3848 & 93274
3/4” NPT for Stock# 90836
Before each use
Inspect your work area Inspect your compressor
1. Keep work area clean. Cluttered areas and
benches invite accidents.
2. The floor must not be slippery from wax or
dust.
1. To reduce the risk of injury from accidental
starting, turn the switch off and disconnect
power.
2. If any part is missing, bent or broken in any
way, or any electrical part does not work
properly, keep the compressor off and dis connect power. Do Not use if defect is found.
3. Check hoses for weak or worn condition
before each use, making certain all connect ions are secure. Do Not use if a defect is
found.
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Follow the safety precautions for electrical connections
1. Follow all local electrical and safety codes,
as well as the National Electric Code (NEC)
and the Occupational Safety and Health
Act (OSHA).
2. Wiring and fuses should follow electrical
codes, current capacity and be properly
grounded.
Plan ahead to protect your eyes, hands, face and ears
Dress for safety
1. Wear safety glasses (meeting ANSI Z87.1 or
in Canada CSA Z94.3-99) and use hearing
protection when operating the unit. Everyday
glasses are not safety glasses.
2. Wear shoes to prevent shock hazards.
3. Tie back long hair.
Pay attention to your hands
WARNING
Keep fingers away from running compressor.
Fast moving and hot parts may cause injury
and/or burns.
3. Protect wires from contact with sharp objects.
CAUTION
All electrical connections should be made by
a qualified electrician.
WARNING
Be careful when touching the exterior of compressor, pump, motor and air lines; they may
become hot enough to cause injury.
WARNING
Never operate the compressor without a
beltguard. The compressor can start automatically without warning. Personal injury or
property damage could occur from contact
with moving parts.
CAUTION
The compressor may be hot even if the unit is
stopped.
When operating
1. Do not exceed the pressure rating of any
component of the system.
2. Release pressure within the system slowly
to prevent flying dust and debris.
3. If the equipment starts to abnormally vibrate,
STOP the compressor immediately and
check for the cause.
WARNING
Use of a mask or respirator per chemical
manufacturers’ instructions may be necessary if there is a chance of inhaling toxic fumes.
Read mask and respirator instructions carefully. Consult a safety expert if you are not
sure about the use of certain masks or
respirators.
WARNING
Never change the safety valve or pressure
switch settings. Keep safety valve free from
paint and other accumulations. See compressor
specification decal for maximum operating
pressure. Do not operate with the pressure
switch set higher than the maximum operating
pressure.
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Spraying precautions
WARNING
Never point a spray gun at yourself or any
other person or animal. Accidental discharge
may result in serious injury.
Reduce the risk of dangerous
environment
WARNING
Extreme caution should be taken when
spraying flammable liquids as the spark from
a motor or pressure switch may cause a fire
or explosion. Ample ventilation must be
provided.
WARNING
Spray in a well ventilated area to keep fumes
from collecting and causing serious injury and
fire hazards.
Perform these maintenance operations
1. Do Not spray in the vicinity of open flames
or other places where a spark can cause
ignition. Do Not smoke when spraying
paint, insecticides, or other flammable
substances.
Be informed about the materials you use
1. When spraying with solvents or toxic chemi cals, follow the instructions provided by the
chemical manufacturer. Consult a safety
expert if unsure about the use of masks or
respirators.
2. If the material you intend to spray contains
trichloreoethane and methylene chloride, do
not use accessories that contain aluminum or
galvanized materials, as these chemicals can
react with galvanized components causing
corrosion and weakening equipment. Use
stainless steel accessories.
1. Do regular maintenance; keep all nuts, bolts,
and screws tight, to be sure equipment is in
safe working condition.
2. Inspect tank yearly for rust, pin holes or any
other imperfections that could cause it to
become unsafe.
WARNING
NEVER attempt to repair or modify a tank!
Welding, drilling or any other modification will
weaken the tank resulting in damage from
rupture or explosion. Always replace worn,
cracked or damaged tanks.
3. Clean electrical equipment with an approved
cleaning agent, such as a dry, non-flam mable cleaning solvent.
Daily
Check oil level at sight glass.
Drain moisture from tank.
Verify the pressure switch unloader is
working by listening for a brief hissing sound
when the compressor shuts off.
4. Drain tanks of moisture after each day’s use.
If unit will not be used for awhile, it is best to
leave the drain cock open until such time as it
is to be used. This will allow moisture to
completely drain out and help prevent
corrosion of inside of tank.
5. Always disconnect from power source before
working on or near a motor, or its connected
load. If power disconnect point is out-of sight, secure it in the “OFF” position and tag it
to prevent unexpected application of power.
WARNING
Disconnect power and depressurize system
before servicing air compressor. Slightly open
drain cock after shutting off compressor.
Monthly
(Make sure the main power is off.) Check the belts
for tension. Belts should not move up and down
when the compressor runs and when stopped,
should not have more than ½ in of play when
depressed. Be careful not to over tighten belts
during adjustment.
Remove and check air filter, replace if necessary.
Visually check the compressor for loose parts,
excessive noise or vibration.
Change oil every 3 months or 300 hours. A
compressor grade non-detergent oil should be
used. (40 wt for 3848 and 30wt for Models
93274 and 90836).
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WARNING LABELS
Find and read all warning labels found on the air compressor.
WIRING
GLOSSARY OF TERMS
Air Filter
Porous element contained within a metal or
plastic housing attached to the compressor
cylinder head which removes impurity from the
intake air of the compressor.
Air Tank
Cylindrical component which contains the
compressed air.
Check Valve
Device which prevents compressed air from
flowing back from the air tank to the compressor pump.
Electric Motor
Device which provides the rotational force
necessary to operate the compressor pump.
Pressure Switch
Device which automatically controls the on/off
cycling of the compressor. It stops the
compressor when the cut-off pressure in
the tank is reached and starts the compressor
when the air pressure drops below the cut-in
pressure.
PSI (Pounds per Square Inch)
Measurement of the pressure exerted by the
force of air. The actual psi is measured by a
pressure gauge on the compressor.
Pump
Device which produces the compressed air
with a reciprocating piston contained within a
cylinder.
Safety Valve
Pressure Gauge
Device which shows the tank or regulated
pressure of the compressed air.
Device which prevents air pressure in the air
tank from rising over a predetermined limit.
Thermal Overload Switch
Device, integrated into the electric motor winding,
which automatically “shuts off” the compressor
if the temperature of the electric motor exceeds
a predetermined limit.
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WIRING
WIRING
WARNING
ALL ELECTRICAL WIRING SHOULD BE DONE
BY A QUALIFIED ELECTRICIAN
General Information
Adequate wiring and motor protection
should be provided for all stationary
compressors. Wiring used for other
machinery should not be used. A
qualified electrician familiar with local
electrical codes in your area should be
used. Size supply wiring per NEC (National
Electric Code) requirements.
WARNING
To reduce the risk of electrical hazards, fire
hazards or damage to the compressor, use
proper circuit protection. Your compressor
is wired at the factory for operation using
the voltage shown. Connect the compressor
to a power source with the correct breaker
size.
WARNING
Electrical connections must be properly
grounded. Ground connections should be
connected at the grounding screw.
For Models 3848 & 93274
Incoming power should
be connected to the
posts marked (line)
Do Not Make
Connections On
Prewired Posts (Motor)!
Grounding Screw
3848
Voltage
Full Load Amps
Breaker Size
230V / 1 ph
Incoming power should
be connected to L1 and
L2 at the Top of the
Magnetic Starter.
For 90836
93274
230V / 1 ph
16
23
40 amp30 amp
90836
230V / 1 ph
32
60 amp
CAUTION
Overheating, short circuiting and fire damage
will result from inadequate wiring.
STARTING THE COMPRESSOR
STARTING THE COMPRESSOR
Prior to actually running the compressor,
check the following items:
Crankcase oil - Make sure the sight glass
shows ½ full or slightly above.
Make sure all rags, tools, oil, etc. are away
from the unit.
Open the air system to free it of any pressure.
Switch the compressor on for a few
revolutions to make sure the rotation is
correct. Correct rotation is clockwise
when facing the sight glass on the pump.
Ground
Operate the compressor for a few minutes
unloaded (air system open) then allow the
compressor to pump up. Make sure the
electrical pressure switch properly switches
off the compressor according to the setting
desired. (130 psi for 3848, 165 for 93274,
and 175 psi for 90836.)
CAUTION
Make sure the pressure in the tank does
not exceed its rating. 3848 should
operate at a maximum of 130 psi, 93274
should operate at a maximum of 165 psi,
& 90836 at a maximum of 175 psi. If the
pressure gauge indicates a pressure that
is higher than these maximum pressures,
shut off compressor immediately and call
1-866-869-3114.
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TROUBLESHOOTING GUIDE
Low discharge pressure
Excessive noise
“knocking”
Excessive oil carryover
1. Compressor too small for
application
2. Air leaks
3. Restricted intake air
4. Blown gasket(s)
5. Broken or misaligned valves
1. Loose drive pulley or flywheel
2. Low on oil
3. Worn connecting rod or
connecting rod bearing
4. Noisy check valve
1. Worn piston rings
2. Restricted intake air
3. Too much oil in compressor
4. Incorrect oil viscosity
1. Reduce air demand or use a compressor
with more air capacity.
2. Listen for air leaks. Apply a soap solution
to all fittings and connections. Bubbles
will form at points of leakage. Tighten
or replace fittings or connections.
3. Clean or replace air filter.
4. Replace necessary gaskets.
5. Remove head and inspect for broken or
misaligned valves. Replace valves, if
necessary.
Install a new head gasket
!
CAUTION
each time head is removed
1. Tighten drive pulley or flywheel bolt.
2. Check for proper oil level. Low or dirty
oil may cause bearing damage.
3. Replace connecting rod and/or connecting
rod bearings.
4. Replace check valve.
!
DANGER
with air pressure in tank
1. Replace with new piston rings.
2. Clean or replace air filter.
3. Drain oil to proper oil level.
4. Use a quality non-detergent 30 or 40wt
oil specified for each model (Page 4).
Do not remove check valve
Water in tank and/or
discharge line
Will not run or motor
hums
Breaker or reset
repeatedly trips
Tank does not hold
pressure when not
running and shut off
valve is closed
1. Normal. Amount of water will
increase as humidity in the
air increases.
1. Low voltage
2. Malfunctioning pressure switch
3. Malfunctioning check valve
1. Incorrect breaker size
2. Low voltage
3. Malfunctioning motor
4. Loose electrical connections
5. Malfunctioning pressure switch
6. Malfunctioning check valve
1. Malfunctioning check valve
2. Loose fittings or connections
3. Crack or pin hole in tank
1. Drain tank at least once per day.
2. Add an inline filter to reduce moisture in
in the air line.
1. Check voltage with volt meter across both
legs of incoming power. Check reset button
on motor.
2. Repair or replace pressure switch.
3. Replace check valve or pressure switch.
Do not remove check valve
!
DANGER
with air pressure in tank
1. Make sure the breaker is sized properly.
See page 6 in this manual.
2. Check voltage with volt meter across both
legs of incoming power.
3. Replace motor.
4. Check all electrical connections.
5. Adjust or replace pressure switch.
6. Replace check valve.
Do not remove check valve
!
with air pressure in tank
DANGER
1. Replace check valve.
Do not remove check valve
!
DANGER
with air pressure in tank
2. Tighten or replace fittings or connections.
3. Replace tank. Do not attempt to repair tank.
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TROUBLESHOOTING GUIDE (Continued)
Pressure switch unloader constantly
leaking air
Pressure switch not
unloading
Excessive vibration
Overheating
1. Malfunctioning check valve
1. Malfunctioning pressure
switch
1. Improper installation
2. Loose belts
3. Misaligned flywheel or
drive pulley
1. Compressor too small for
application
2. Cooling surfaces dirty
3. Improper cooling
1. Replace check valve if unloader bleeds
constantly.
Do not remove check valve
!
DANGER
with air pressure in tank
1. Replace pressure switch if it does not release
air pressure briefly when unit shuts off.
Do not remove pressure
switch with air pressure in
!
DANGER
tank
1. Make sure unit is mounted on a level surface
with vibration pads.
2. Replace belts. Align and tighten properly.
3. Align flywheel and drive pulley.
1. Reduce air demand or use a compressor
with more air capacity.
2. Clean all cooling surfaces of dirt and dust.
3. Install compressor in an area with adequate
cool dry air.
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02
08
09
01
10
03
05
06
04
Illustration Part Description
Number
3848
1 Compressor B3800
2 Air Filter 6229020500
3 Electric Motor 1312100390
4 Safety Valve 1312100005
5 Pressure Switch 1312100455
6 Tank Gauge 1312100006
7 Tank Drain
8 Check Valve 1312100168
1312100360
9 Discharge Tube 1312100215
10
Belt Guard
(2 Part Numbers)
6222019500
6214343100
Drive Belts 1312100134
Drive Pulley 1312100442
11
*Part Numbers Subject to Change Without Notice
Compressor Support: 866-869-3114
07
11
93274
T29S
FS008
1312100387
1310251870
1312100459
1312100028
1312100360
1312100168
1312100214
1312100145
1312100146
1312100133
1312100442
90836
B6000
FS002
1312100400
9710533300
1312100510
1312100028
1312100360
1312100169
1312100208
1312100148
1312100150
1312100140 (2)
1312100420
DP75HP1
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LIMITED
WARRANTY
Harbor Freight Tools Co. makes every effort to assure that its products meet high
quality and durability standards, and warrants to the original purchaser that this
product is free from defects in materials and workmanship for a period of one year
(3848) or two years (3847, 93274, and 90836) from date of purchase
(90 days if used by a professional contractor or if used as rental equipment).
This warranty does not apply to damage due directly or indirectly to misuse, abuse,
negligence or accidents; repairs or alterations outside our facilities; or lack of
maintenance. We shall in no event be liable for death, injuries to persons or
property, or for incidental, contingent, special or consequential damages arising
from the use of our product.
Some states do not allow the exclusion or limitation of incidental or consequential
damages, so the above limitation of exclusion may not apply to you. To take
advantage of this warranty, the product or part must be returned to us with
transportation charges prepaid. Proof of purchase date and an explanation of the
complaint must accompany the merchandise. If our inspection verifies the defect,
we will either repair or replace the product at our election or we may elect to refund
the purchase price if we cannot readily and quickly provide you with a replacement.
We will return the repaired products at our expense, but if we determine there is no
defect, or that the defect resulted from causes not within the scope of our warranty,
then you must bear the cost of returning the product. This warranty gives you
specific legal rights and you may also have other rights which vary from state to
state.
3491 Mission Oaks Blvd. PO Box 6009 Camarillo, CA 93011 (800)444-3353
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