SMC Networks IDU3E-23-C User manual

IDX-OM-K037-C
Initial issue: October, 2006
3nd edition: November, 2016
PRODUCT NAME
Refrigerated Air Dryer
MODEL / Series
IDU3E-23-C,K,L,R,T,V
IDU4E-23-C,K,L,R,T,V
IDU6E-23-C,K,L,R,T,V
Please read this manual prior of using the air dryer.
Keep the manual readily available for reference.
© 2016 SMC CORPORATION All Rights Reserved.
Operation Manual

Dear Customers
Thank you for selecting SMC RefrigeratedAir Dryer.
This operationmanualmust be read and understood thoroughly before using the product. It provides all essential
information pertaining to safety, as well as, maximizing product efficiency in order to extend the life of the product.
In addition, it is strongly recommended that you follow all the safety guidelines and regulations set forth by the
local government agencyfor proper installation and usage.
This manual explains about installation and trial operation of the product. These tasks should be performed only
byindividuals with the proper training and have a good understanding of the air dryer.
There is no production amends or financialcompensation due to dryers trouble.
This manual contains confidential information proprietary to SMC. It must not be reproduced or disclosed to
others, or used in anyother way, in part or in whole, except as authorized in writing by SMC.
Caution: Please understand that the contents of this operation manual are subjected to
change without prior notice.

Table of Contents
Table of Contents - 1
To Customers
Chapter i Safety Instructions
i - 1 Warning: Before Using Air Dryer.........................................................i - 1
i - 1 - 1 Hazard, Warning, and Caution Used in This Manual....................................i - 1
i - 2 Danger Classifications/Position of Hazard warning Label........i - 2
i - 2 - 1 Danger Classifications..................................................................................i - 2
i - 2 - 2 Hazard of Electricity .....................................................................................i - 3
i - 2 - 3 Hazard of Hot Surface..................................................................................i - 3
i - 2 - 4 Hazard of Rotating Fan Motor ......................................................................i - 3
i - 2 - 5 Danger of CompressedAir Circuit................................................................i - 3
i - 2 - 6 Positions of Hazard Warning Label...............................................................i - 4
i - 2 - 7 Hazard of Refrigerant...................................................................................i - 5
i - 2 - 8 Cautions about Usage..................................................................................i - 6
i - 2 - 9 Other Label ..................................................................................................i - 6
i - 3 Disposal.......................................................................................................i –7
i - 4 Limited warranty and Disclaimer / Compliance Requirements ........i –8
Chapter 1Parts Name and Functions
1 - 1 Parts Names and Functions................................................................ 1 - 1
Chapter 2Transportation / Installation
2 - 1 Transportation.......................................................................................... 2 - 1
2 - 2 Installation.................................................................................................. 2 - 2
2 - 2 - 1 Location ..................................................................................................... 2 - 2
2 - 2 - 2 Anchorage.................................................................................................. 2 - 3
2 - 2 - 3 Air piping.................................................................................................... 2 - 3
2 - 2 - 4 Drain Tube.................................................................................................. 2 - 3
2 - 2 - 5 Electric Wiring............................................................................................ 2 - 4
2 - 3 Cautions about reinstallation............................................................. 2 - 6
Chapter 3Operation / Shutdown
3 - 1 Check points before operation .......................................................... 3 - 1
3 - 2 Operation.................................................................................................... 3 - 1
3 - 3 Shutdown................................................................................................... 3 - 2
3 - 4 Cautions about restart........................................................................... 3 - 2
3 - 5 Check points before restart................................................................. 3 - 2
3 - 6 Precautions for long-term non-operation...................................... 3 - 2
Chapter 4Maintenance
4 - 1 Daily inspection....................................................................................... 4 - 1
4 - 2 Periodical maintenance........................................................................ 4 - 1
4 - 2 - 1 Cleaning the condenser and aftercooler fins............................................... 4 - 1
4 - 2 - 2 Service parts .............................................................................................. 4 - 1
4 - 2 - 3 Cleaning of Auto Drain Strainer .................................................................. 4 - 1
Chapter 5Troubleshooting............................................................................................ 5 - 1
Table of Contents

Table of Contents
Table of Contents - 2
Chapter 6 References
6 - 1 Specifications...........................................................................................6 –1
6 - 2 Refrigerant with GWP reference........................................................ 6 - 1
6 - 3 Dimensions................................................................................................ 6 - 2
6 - 4 Electrical Circuit...................................................................................... 6 - 2
6 - 5 Compressed Air and Refrigerant Circuit / Operation Principles.....6 - 3
Chapter 7 Option Specification C
7 - 1 Safety instructions.................................................................................. 7 - 1
7 - 2 Precautions for the installation and handling of the product 7 - 1
7 - 3 Specifications........................................................................................... 7 - 1
Chapter 8 Specification for Option K
8 - 1 Safety instructions.................................................................................. 8 - 1
8 - 2 Specifications........................................................................................... 8 - 2
Chapter 8 Specification for Option L
9 - 1 Safety instructions.................................................................................. 9 - 1
9 - 2 Specification.............................................................................................. 9 - 1
9 - 3 Specification of heavy duty auto drain (ADH4000-04).............. 9 - 2
9 - 4 Installation of heavy duty auto drain............................................... 9 - 2
9 - 5 Maintenance.............................................................................................. 9 - 2
Chapter 9 Specification for Option R
10 - 1 Safety instructions................................................................................ 10 - 1
10 - 2 Specifications of the GFCI................................................................. 10 - 2
10 - 3 How to connect the power supply.................................................. 10 - 2
Chapter 10 Specification for Option T
11 - 1 Safety instructions.................................................................................11 - 1
11 - 2 Specifications..........................................................................................11 - 1
11 - 3 Remote operation...................................................................................11 - 2
11 - 4 How to connect the power supply and signal cable.................11 - 2
11 - 5 Electric circuit..........................................................................................11 - 3
Chapter 12 Specification for Option V
12 - 1 Safety instructions................................................................................ 12 - 1
12 - 2 Specifications......................................................................................... 12 - 2
12 - 3 How to perform maintenance........................................................... 12 - 2
Chapter 13 Service Record
13 - 1 Service Record....................................................................................... 13 - 1

i Safety Instructions
i- 1
iSafety Instructions
Be sure to read and comprehend important cautionary
notifications in this operation manual before use
i-1 Warning: Before Using Air Dryer
In this chapter, the stated contents are especially about safety.
This Air Dryer is installed downstream of the air compressor to remove moisture. The manufacturer is not
responsible for any misuses or misapplications.
This air dryer operates with high voltage and hot surfaces during operation. In addition, this air dryer
has high speed rotating fan and motor, which can cause serious injury upon accidental contact. It is
advised that you contact the factory or SMC authorized dealer for spare parts or other servicing needs.
We strongly recommend that any one who is working with this air dryer need to read and understand the
instructions in this manual beforehand. Often, it’s necessary for the people involved, to receive training
in order to address the issues of safety and proper application.
When short period power shortage (including instantly recovered shortage) is recovered, it may take a
longer starting period than usual starting or may not start due to the protective devices.
In this case, turn off the ON-OFF switch on dryer panel and wait 3 minutes. After this step, turn on the
switch to restart. Whenever open the cover panel of this unit, do not miss to turn off the ON-OFF switch,
because dryer may start itself when the power supply is recovered.
Connections to a power source where the product is exposed to transient stresses exceeding
overvoltage category II (as defined in IEC60664-1).
Only connect to TN-S power distribution systems with N conductively connected to PE.
i-1-1 Hazard, Warning, and Caution Used in This Manual
This product is designed with the first priority on safety. However, there are some inherent risks
that cannot be eliminated. This manual classifies these risks into the following three categories
according to the severity: DANGER, WARNING and CAUTION. Read the warning statements
carefully and thoroughly understand them before operating or performing maintenance on the unit.
DANGER
“DANGER”indicates that there is an imminence hazard that will cause serious
injury or death if not avoided.
Do not operate the product without the cover panel.
WARNING
“WARNING”indicates that there is a hazard that may cause serious injury or
death if not avoided.
CAUTION
“CAUTION”indicates that there is a hazard that may cause minor injury.

i Safety Instructions
i- 2
i-2 Danger Classifications & Position of Hazard warning Labels
To help you recognize the hazards, the unit utilizes special graphics to indicate different hazards. Confirm the
contents of the hazards and the location of the labels before operation.
Warning
Only properly trained, qualified personnel are allowed to perform tasks such as:
Operation, installation, relocation of product and maintenance works.
Should any problem occurs, address it according to instruction in this manual.
Identify problems following the guidelines in Chapter 5 for Troubleshooting before
proceed with maintenance works.
The product should not be turn on in the event of any problems.
When the product gets out of order, shutdown immediately, and contact for
service
i-2-1 Danger Classifications
Specific danger classification of this product is as follows.
Hazard of Electricity
Since this product operates with high voltage, there is the danger of electric
shock. This special symbol is used, along with key words: “CAUTION”, “WARNING”
or “DANGER”, on the product and in this manual.
Hazard of Hot Surface
Since this product becomes hot while running, there is the danger of burn injury.
This special symbol is used, along with key words: “CAUTION”,“WARNING” or
“DANGER”, on the product and in this manual.
Hazard of Rotor
Since this product has parts that rotate at high speed while running, there is the
danger of bodily injury. This special symbol is used, along with key words: “CAUTION”,
“WARNING” or “DANGER”, on the product and in this manual.

i Safety Instructions
i- 3
i-2-2 Hazard of Electricity
Warning
Inside of this product, there is a power-supplying section with high voltage separated
by the cover panel. Do not operate the product with the cover panel off.
i-2-3 Hazard of Hot Surface
Warning
Since this product has parts that become hot during operation, there is the danger of
burn-associated injuries. These parts remain hot even after power is off. Wait until the
unit has cooled down before touching.
i-2-4 Hazard of Rotating Fan Motor
Warning
Since this product has parts that rotate during operation, there is the danger of injury
resulting from direct contact. The fan and rotor will start/stop automatically. Thus, do
not work on them when power is on.
i-2-5 Danger of Compressed Air Circuit
Warning
Before replacing or cleaning parts, be sure to relief the pressure remained inside of the
product until the gauge indicates “0”. High pressure can propel object at high velocity
and cause injury.

i Safety Instructions
i- 4
i-2-6 Positions of Danger Warning Label
Warning
Read with caution and pay attention to the notations of danger warning labels.
Do not remove or rub danger warning labels.
Confirm the positions of danger warning labels.
Front
WARNING 警告
!
1 Remove panels for maintenance only.
2 Never insert anything into product to ensure
safety.
3 Cut power prior to maintenance to prevent
electric shock.
4 Settle product to room temp.before main-
tenance toprevent burn or frostbite.
5 Ensure zero air pressure before replacing parts.
1 点検以外はﾊﾟﾈﾙを取り外さないこと。
2 回転物があるので指、棒状の物を差し
込まないこと。
3 感電の恐れがあるので、点検の前には電源を
切ること。
4 火傷の恐れがあるので、点検の前には装置を
常温にすること。
5 部品交換の前には必ず、空気圧力を"0"に
すること。
!

i Safety Instructions
i- 5
Front
i-2-7 Hazard of Refrigerant
Caution
This product uses Fluorocarbon (HFC) as a refrigerant.
It is strictly forbidden to emit Fluorocarbon into the atmosphere. Before you repair the
refrigerant circuit, you should collect the refrigerant with proper evacuation system.
The collected refrigerant should be properly recycled by qualified agency. Only
personnel with proper credential are allowed to handle refrigerant.
Only properly trained qualified personnel are allowed to remove the cover panel of the
product.
The quantity and the type of Fluorocarbon are mentioned on the specification label.
See Page i - 6.

i Safety Instructions
i- 6
i-2-8 Cautions about Usage
Warning
Please follow the instructions on all warning labels. Do not remove or deface
warning labels, and confirm the location of warning labels.
i-2-9 Other Label
Front
Front
CAUTION 注意
!
1 Read manual before operation.
2 Ensure vantilation and maintenance
space.
3 Keep water away from the product.
4 Secure In / Out connector with spanner
during piping.
5 Wait 3 minutes before restart.
6 Ensure Running Condition / Evaporating
Temp. in green zone.
1 ご使用前に必ず取扱説明書を読んでください。
2 通風、メンテナンススペースを確保して
ください。
3 雨や水滴がかからないようにしてください。
4 ＩＮ／ＯＵＴポートをスパナで固定して
配管してください。
5 再起動は運転停止３分後に行ってください。
6 ＲＵＮＮＩＮＧ ＣＯＮＤＩＴＩＯＮ・蒸発温度計は
グリーン帯で使用してください。
Specification Label

i Safety Instructions
i - 7
i-3 Disposal
When you dispose of the product, you should collect the refrigerant and the refrigerant oil inside the refrigerant
circuit.
Caution
This product contains Fluorocarbon HFC.
It is strictly forbidden to emit Fluorocarbon into the atmosphere. Before you
repair the refrigerant circuit, you should collect the refrigerant with proper
evacuation system. The collected refrigerant should be properly recycled by
qualified agency. Only personnel with proper credential are allowed to
handle refrigerant.
Only properly trained and qualified personnel are allowed to remove the
cover panel of the product.
The quantity and the type of Fluorocarbon are mentioned on the
specification label. See Page i - 6.
Caution
Dispose of the refrigerant and refrigerant oil according to the regulation of
local government.
Only personnel with proper credential are allowed to collect refrigerant and
refrigerant oil.
Only properly trained and qualified personnel are allowed to remove the
cover panel of the product.
For any questions, please contact our factory or SMC authorized dealers.

i Safety Instructions
i - 8
i –4 Limited warranty and Disclaimer / Compliance Requirements
The product used subject to the following “Limited warranty and Disclaimer“and “Compliance Requirements.
Read and accept them before using the product.
Limited warranty and Disclaimer
1. The warranty period of the product is 1 year in service or 1.5 years after the product is delivered.
Also, the product may have specified durability, running distance or replacement parts. Please consult
your nearest sales branch.
2. For any failure or damage reported within the warranty period which is clearly our responsibility, a
replacement product or necessary parts will be provided.
This limited warranty applies only to our product independently, and not to any other damage incurred
due to the failure of the product.
3. Prior to using SMC products, please read and understand the warranty terms and disclaimers noted in
the specified catalog for the particular products.
Compliance Requirements
1. The use of SMC products with production equipment for the manufacture of weapons of mass
destruction (WMD) or other weapon is strictly prohibited.
2. The exports of SMC products or technology from one country to another are govemed by the relevant
security laws and regulation of the countries involved in the transaction. Prior to the shipment of a SMC
product of a SMC product to another country, assure that all local rules goveming that export are known
and followed.
Caution
The Product is provided use in manufacturing industries.
The product herein described is basically provided for peaceful use in manufacturing industries.
If considering using the product in other industries, consult SMC beforehand and exchange
specifications or a contact if necessary.
If anything is unclear, contact your nearest sales branch.

1 Name and Functions Parts
1 - 1
1 Parts Name and Functions
1-1 Parts Name and Functions
•IDU3E to 6E
Front
Switch with Lamp
The lamp is continuously ON
during normal operation.
Evaporation Thermometer
Indicates the evaporating
temperature of refrigerant on
low-pressure side.
During normal operation, the
indicator remains in the
green zone.
Ventilation Grille
Hot air will be exhausted by
condenser fan. Do not block
these vents.
Panel Lock (x 2)
Another one is on opposite side
Drain Tube
Discharges drain.
Auto Drain
Do not remove the insulation on
the auto drain.
View with Front Panel removed
IDU3E to 6E

1 Name and Functions Parts
1 - 2
•IDU3E to 6E
Rear Panel
You can see the terminal block when you
remove this cover. Connect the power
cable through the membrane grommet.
Rubber Grommet
Power cord inlet
Front
L
N
PE
Customer Connection Side
Terminal Connecting Screw: M3
Ring terminals: 1.25-3
(Width 6.5mm and below)
(Screw head dimension: 0.25”(6.5mm)
（）

2 Transportation / Installation
2 - 1
2 Transportation / Installation
Warning
Only properly trained, qualified personnel are allowed to perform tasks such as:
Operation, installation, relocation of product and maintenance works.
Strongly recommend to prepare the spare dryer when applying the dryer for
important product or system.
2 - 1 Transportation
When you transport the product, you should follow the instructions below:
You should lift the product from the base surface with careful attention to prevent tipping over.
Do not lay the product sideways, or you will damage the product.
Do not suspend the product from the ceiling or hang from the wall.
Do not transport the product with any part such as an air filter mounted on the fittings at the air inlet or
outlet port of the product. If it is unavoidable to transport the product with such a part mounted, support
the mounted part with a bracket to prevent the product from being affected by vibration during
transportation.
Warning
This product is heavy.
Each model IDU3E to 6E weights about 20kg or more. It must be transported by more
than one person, a forklift is necessary.

2 Transportation / Installation
2 - 2
2 - 2 Installation
2-2-1 Location
The product should not be used or stored in the following conditions: Those conditions will cause
not only malfunction but also failures.
Environment where the product is exposed to
rainwater, moisture, salt water or oil.
Locations where the product is exposed to dust
or particles
Locations where the product is exposed to
flammable, combustible or explosive fumes.
Locations where the product is exposed to
corrosive gas or solvent.
Locations where the product is exposed to
direct sunlight or radiated heat.
Locations where ambient temperature is
beyond following range:
On-stream: 2 to 40oC
Storage: 0 to 50oC (when there is no drain
water inside of the piping)
Locations where temperature changes rapidly.
Locations where strong electromagnetic noise
is generated.
Circumstances where static electricity is
produced or discharged through the body of the
product.
Locations where strong high frequency shock
wave is generated
Locations where danger of thunder is apparent.
Locations where loading on vehicles, marine
vessels, and so on
Locations where altitude is higher than 2,000
meters
Circumstances where strong vibration or impact
are transmitted.
Circumstances where too much force and
weight are put on the body of the product that
causes it to deform.
Circumstances where not enough clearance
spaces to do maintenance
Spaces needed for maintenance
Front : 600 mm
Rear : 600 mm
Top : 600 mm
Right : 600 mm
Left : 600 mm
Locations where ventilation grille of the product
can be blocked.
Locations where the dryer could intake warm air
(for example from a compressor or other
dryers).

2 Transportation / Installation
2 - 3
2-2-2 Anchorage
The air dryer should be installed on a vibration-free, stable, horizontal, flat surface.
Refer to “Chapter6 6-2 Dimensions” for the dimensions.
IDU3E~6E should be bolted by anchor bolts to prevent falling. We recommend the anchor bolt sets that we are
selling separately as accessories.
2-2-3 Air piping
Connection to the inlet and outlet of compressed air should be made removable by using union and so on.
Pressing the hexagonal fitting with screw wrench and so on, connect the air piping fittings to the body.
When mounting any part such as an air filter on the fitting at the compressed air inlet or outlet port, support the part
to prevent excessive force from being applied to the product.
Be careful not to let the vibration of the air compressor transmit.
If the temperature of compressed air on the inlet side is higher than 50oC, place an aftercooler after the air
compressor. Or, make the temperature of the place where the air compressor is installed lower than 50oC.
Flash the piping sufficiently in order to avoid any foreign substances such asdust, sealing tape, liquid gasket, etc.
when piping before piping connection.Foreign substances in the piping can cause cooling failure or drainage
failure.
Use pipes and fittings that have enough endurance against the operating pressure and temperature. And
connect it firmly to prevent air leakage.
Provide bypass piping to make it possible to do maintenance without stopping the air compressor.
The bypass piping sets
2-2-4 Drain Tube
Apolyurethane tube (10mm) O.D. is attached tothe autodrain. The end of the tube is open to atmosphere to let drain
flow through the tube into a collector or drain pipe.
The compressed air is used to push out the drain periodically. Fix the outlet end of the tube in order to prevent
whipping action during discharge.
Install the drain tube in such a way so that no drain is trapped.
During installation, make sure the dryer does not sit on the drain tube which is at the bottom of the unit. Be careful to
avoid the dryer from crushing the tube during installation.
We recommend the bypass piping sets that
we are selling separately as accessories.

2 Transportation / Installation
2 - 4
Warning
To handle drain discharge, follow the safety guidelines such as wearing protective
goggles, apron, and gloves.
In case that oil gets mixed in the wastewater discharged from the auto drain, the liquid would be
considered as toxic waste and treatment is necessary in accordance with local regulations.
2-2-5 Electric Wiring
Warning
Only properly trained and qualified personnel are allowed to perform wiring work.
・Before wiring, you must disconnect the power. Do not work under any energized
conditions.
・Supply power from a stable source that is free from the effect of surge.
・Ensure that a Ground Fault Circuit Interrupter(GFCI) with appropriate capacity for earth
leakage and load is used in the power supply of the product to prevent electrical shock
and burnout of the compressor motor. See “6-1 List of specifications” for details.
・Supply power of the product should meet the specifications on page 6-1.
・The product must be grounded for safety.
・Do not connect ground wire to a water pipe, a gas pipe, or a lightening rod.
・Do not plug too many leads into a single cocket.
・Circuit breaker must be properly selected to meet safety standard of local regulations.
・Always be sure to connect the protective conductor first, disconnect it last in respect to
the other connections.
・Be sure that the protective conductor has some additional length in respect to the live
conductors, so that it is not subject to mechanical stresses.
・Be sure to install the circuit breaker correctly so that it disconnects all live conductors
and so that the operating handle can be easily accessible.
Specification of power cable
Prepare following power cable.
Power cable: 1.25mm2(16AWG), Three-cores (including the ground cable), External diameter: about 8 to 12mm.
Additional length of about 0.1m (4in) is needed to wire inside of the product.
Length of the power cable
The maximum length of the power cable should be no more than 98ft (30m).
Connecting to the power supply
Connect the power cable and the ground tothe terminal block. Make sure to use the ring terminals for M3 screws.
Applicable crimped terminal: 1.25-3 (Width: 6.5mm and below)

2 Transportation / Installation
2 –5
Wiring procedure
Remove the terminal block cover or the rear panel.
Insert the cord through the rubber grommet and connect it to the terminal block (refer to the label on
the terminal block). M3 screw tightening torque: 0.6 to 1Nm
During wiring work, do not touch other sections except terminal block.
Re-attach the cover or real panel after wiring is done.
2 - 3 Cautions for Reinstallation
Caution
Only properly trained, qualified personnel are allowed to perform reinstallation.
If the product is moved and reinstalled in another place after some trial operations, the following instructions
must be followed as well as procedures in Chapter 2.
Removing the power cable
Disconnect the power source before removing the power cable.
Warning
Only properly trained, qualified personnel are allowed to perform wiring.
Disconnect the power source before wiring. Do not work under energized condition
Disconnecting air pipes
Warning
Only properly trained, qualified personnel are allowed to perform piping works.
Separate the compressor from the product before disconnecting the air pipe. Do not
disconnect any piping when there is residual air pressure inside of the pipe.
Remove the seal tape completely after removing the piping. Loose seal tape can clog up the system.
Releasing residual pressure
Bypass valve should open even after the dryer has been removed.
Close the compressed air inlet and outlet valve.
Unscrew the front panel screws (in 2 places) and remove the front panel.
Open the auto drain residual pressure release valve to release air pressure inside the product. Refer to the
figure at right.
Case Assembly
The ramainder depressure cock.
※It opens when turning in the
drection og the arrow of figure.

3 Operation / Shutdown
3- 1
3 Operation / Shutdown
Caution
Only properly trained and qualified personnel are allowed to perform
operation/shutdown of the product.
3-1 Check points before operation
Before trial run, check the following points:
Installed Conditions:
By visual inspection , check that the product is level.
Model IDU3E to 6E, make sure the product is tied down with anchor bolts.
Do not place heavy objects on the top of the product. Make sure piping does not add weight to the
product.
Power cord, and the ground should be connected firmly.
Drain tube should be connected correctly.
Make sure the piping for compressed air is connected correctly.
3-2 Operation
Start operation according to the procedure below.
Turn on the breaker of the main power supply. Then, turn on the illuminated ON/OFF switch.
The lamp will light up. Few minutes later, the cooling fan will rotate and hot air will be exhausted from
the ventilation grille.
Location of the ventilation grille: Model: IDU3E to 6E: Right Side Ventilation Grille
Open the IN/OUT side valve slowly. Make sure the bypass valve is completely closed. Confirm there
is no air leaks.
Depending on the condition of compressed air or ambient temperature, the cooling fan sometimes
alternates between start/stop at the beginning. Then, the refrigerant compressor will start and the
pointer of the evaporating temperature will indicate in the green zone. If the pointer indicates higher
than the green zone, refer to “Chapter 5 Troubleshooting.”
After running for a while, moisture will be discharging from the drain tube automatically.
Caution
Avoid frequent On/Off operation, which may cause problems.
The auto drain used for the product has a structure that closes the valve with air pressure
higher than 0.15MPa. Therefore, until the pressure increase, air will be emitting from the
drain outlet at the start of opening the “IN”valve. Keep in mind that sometimes the
pressure cannot increase due to under-sized air compressor.