AHT 20-350 Operating instructions

ISSUE 2008_06
7425MUM020 CANADA
AHT 20-350
REFRIGERATING AIR DRYER
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USER’S MAINTENANCE AND SPARE PARTS MANUAL
Air Cooled

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Dear Customer,
thank you for choosing our product. In order to get the best performances out of this product, please read
this manual carefully.
To avoid incorrect operation of the equipment and possible physical risk to the operator, please read and
strictly follow the instructions contained in this manual.
Note, these instructions are in addition to the safety rules that apply in the country where the dryer is
installed. Before packing for shipment each AHT series refrigerated air dryer undergoes a rigorous test to
ensure the absence of any manufacturing faults and to demonstrate that the device can perform all the
functions for which it has been designed.
Once the dryer has been properly installed according to the instructions in this manual, it will be ready for
use without any further adjustment. The operation is fully automatic, and the maintenance is limited to few
controls and some cleaning operations, as detailed in the following chapters.
This manual must be maintained available in any moment for future references and it has to be
intended as inherent part of the relevant dryer.
Due to the continuous technical evolution, we reserve the right to introduce any necessary change without
giving previous notice.
Should you experience any trouble, or for further information, please do not hesitate to contact us.
IDENTIFICATION PLATE
Model

Serial No.

Code
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Nominal Flow Rate
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Max Air Pressure
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Max Inlet Air Temp.
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Ambient Temp.
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Refrigerant (Type and qty)
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Refrig. Design Pres. HP/LP
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Electric Supply
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Electric Nominal Power
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Fuse Max.
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Manufactured

The product identification plate,
on the back of the dryer, shows
all the primary data of the
machine. Upon installation, fill
in the table copying the data
shown on the identification
plate. These data must always
be referred to the manufacturer
or to the dealer when
information or spares are
needed, even during the
warranty period.
The removal or the alteration of
the identification plate will void
the warranty rights.
TAD0004
Refrig. Design Pres. HP/LP
Max Inlet Air Temp.
Electric Supply
Manufactured
Fuse Max.
Electric Nominal Power
Refrigerant
Ambient Temp.
Nominal Flow Rate
Max Air Pressure
Code
Serial No.
Model
°F
V/ph/Hz
A
W/A
type/oz
psig
°F
scfm
psig
WARRANTY CONDITIONS
For 24 months from the delivery date, the warranty covers faulty parts, which will be repaired or replaced
free of charge, except the travel, hotel and restaurant expenses of our technician.
The warranty doesn’t cover any responsibility for direct or indirect damages to persons, animals or
equipment caused by improper usage or maintenance, and it’s limited to manufacturing faults only.
The right to warranty repairs is subordinated to the strict compliance with the installation, use and
maintenance instructions contained in this manual.
The warranty will be immediately voided in case of even small changes or alterations to the dryer.
To initiate repairs during the warranty period, the data reported on the identification plate must be provided.

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1. SAFETY RULES
1.1 Definition of the Conventional Signs Used in This Manual
1.2 Warnings
1.3 Proper Use of the Dryer
1.4 Instructions for the use of pressure equipment according to PED Directive 97/23/EC
2. INSTALLATION
2.1 Transport
2.2 Storage
2.3 Installation site
2.4 Installation layout
2.5 Correction factors
2.6 Connection to the Compressed Air System
2.7 Electrical connections
2.8 Condensate Drain
3. START UP
3.1 Preliminary Operations
3.2 First Start-up
3.3 Start-up and Shut down
4. TECHNICAL SPECIFICATIONS
4.1 Technical Specifications AHT 20-150 -1 (115/1/60)
4.2 Technical Specifications AHT 20-350 -2 (230/1/60)
5. TECHNICAL DESCRIPTION
5.1 Control panel
5.2 Operation
5.3 Flow Diagram (Air-Cooled)
5.4 Refrigerating compressor
5.5 Condenser
5.6 Filter Drier
5.7 Aftercooler
5.8 Pre-filter (3 micron)
5.9 Capillary Tube
5.10 Alu-Dry Module
5.11 Hot Gas By-pass Valve
5.12 Refrigerant Pressure Switches PA-PB-PV
5.13 Safety thermo-switch TS
5.14 DMC14 Electronic instrument (Air Dryer Controller)
5.15 Electronic level controlled condensate drain Bekomat 31 AHT 20-100
5.16 Electronic level controlled condensate drain Bekomat 32 AHT 150-350
5.17 Maintenance BEKOMAT
6. MAINTENANCE, TROUBLESHOOTING, DISMANTLING
6.1 Controls and Maintenance
6.2 Troubleshooting
6.3 Maintenance operation on the refrigerating circuit
6.4 Dismantling of the Dryer
7. LIST OF ATTACHMENTS
7.1 Dryers Dimensions
7.2 Exploded View
7.3 Electric Diagrams

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1.1 DEFINITION OF THE CONVENTIONAL SIGNS USED IN THIS MANUAL
Carefully read instruction manual before attempting any service or maintenance procedures on the
dryer.
Caution warning sign. Risk of danger or possibility of damage to equipment, if related text is not
followed properly.
Electrical hazard. Warning message indicates practices or procedures that could result in personal
injury or fatality if not followed correctly.
Danger hazard. Part or system under pressure.
Danger hazard. High temperature conditions exist during operation of system. Avoid contact until
system or component has dissipated heat.
Danger hazard. Treated air is not suitable for breathing purposes; serious injury or fatality may
result if precautions are not followed.
Danger hazard: In case of fire, use an approved fire extinguisher, water is not an acceptable
means in cases of fire.
Danger hazard. Do not operate equipment with panels removed.
Maintenance or control operation to be performed by qualified personnel only 1.
ARIA
AIR
LUFT
AIR
Compressed air inlet connection point.
ARIA
AIR
LUFT
AIR
Compressed air outlet connection point.
Condensate drain connection point.
Operations which can be performed by the operator of the machine, if qualified 1.
NOTE : Text that specifies items of note to be taken into account does not involve safety precautions.
In designing this unit a lot of care has been devoted to environmental protection:
•CFC free refrigerants
•CFC free insulation parts
•Energy saving design
•Limited acoustic emission
•Dryer and relevant packaging composed of recyclable materials
This symbol requests that the user heed environmental considerations and abide with suggestions
annotated with this symbol.
1Experienced and trained personnel familiar with national and local codes, capable to perform the needed activities, identify and
avoid possible dangerous situations while handling, installing, using and servicing the machine. Ensuring compliance to all
statutory regulations.

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1.2 WARNINGS
Compressed air is a highly hazardous energy source.
Never work on the dryer with pressure in the system.
Never point the compressed air or the condensate drain outlet hoses towards anybody.
The user is responsible for the proper installation of the dryer. Failure to follow instructions given in
the “Installation” chapter will void the warranty. Improper installation can create dangerous
situations for personnel and/or damages to the machine could occur.
Only qualified personnel are authorized to service electrically powered devices. Before attempting
maintenance, the following conditions must be satisfied :
•Ensure that main power is off, machine is locked out, tagged for service and power cannot be
restored during service operations.
•Ensure that valves are shut and the air circuit is at atmospheric pressure. De-pressurize the
dryer.
These refrigerating air dryers contain R134a or R404A HFC type refrigerant fluid. Refer to the
specific paragraph - maintenance operation on the refrigerating circuit.
Warranty does not apply to any unit damaged by accident, modification, misuse, negligence or
misapplication. Unauthorized alterations will immediately void the warranty.
In case of fire, use an approved fire extinguisher, water is not an acceptable means in cases of
electrical fire.
1.3 PROPER USE OF THE DRYER
This dryer has been designed, manufactured and tested for the purpose of separating the humidity normally
contained in compressed air. Any other use has to be considered improper.
The Manufacturer will not be responsible for any problem arising from improper use; the user will bear
responsibility for any resulting damage.
Moreover, the correct use requires the adherence to the installation instructions, specifically:
•Voltage and frequency of the main power.
•Pressure, temperature and flow-rate of the incoming air.
•Ambient temperature.
This dryer is supplied tested and fully assembled. The only operation left to the user is the connection to the
plant in compliance with the instructions given in the following chapters.
The purpose of the machine is the separation of water and eventual oil particles present in
compressed air. The dried air cannot be used for breathing purposes or for operations leading to
direct contact with foodstuff.
This dryer is not suitable for the treatment of dirty air or of air containing solid particles.

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1.4 INSTRUCTIONS FOR THE USE OF PRESSURE EQUIPMENT ACCORDING TO
PED DIRECTIVE 97/23/EC
To ensure the safe operation of pressure equipments, the user must conform strictly to the above directive
and the following :
1. The equipment must only be operated within the temperature and pressure limits stated on the
manufacturer’s identification plate.
2. Welding on heat-exchanger is not recommended.
3. The equipment must not be stored in badly ventilated spaces, near a heat source or inflammable
substances;
4. Vibration must be eliminated from the equipment to prevent fatigue failure.
5. Automatic condensate drains should be checked for operation every day to prevent a build up of
condensate in the pressure equipment.
6. The maximum working pressure stated on the manufacturer’s identification plate must not be
exceeded. Prior to use, the user must fit safety / pressure relief devices.
7. All documentation supplied with the equipment (manual, declaration of conformity etc.) must be kept for
future reference.
8. Do not apply weights or external loads on the vessel or its connecting piping.
TAMPERING, MODIFICATION AND IMPROPER USE OF THE PRESSURE EQUIPMENT ARE
FORBIDDEN. Users of the equipment must comply with all local and national pressure
equipment legislation in the country of installation.
2.1 TRANSPORT
Check for visible loss or damage, if no visible damage is found place the unit near to the installation point
and unpack the contents.
•Always keep the dryer in the upright vertical position. Damage to compo
nents could result if unit is laid on
its side or if placed upside down.
•Store machine in a clean, dry environment, do not expose to severe weather environments.
•Handle with care. Heavy blows could cause irreparable damage.
2.2 STORAGE
SCC0001
Even when packaged, keep the machine
protected from severity of the weather.
Keep the dryer in vertical position, also when
stored. Turning it upside down some parts could
be irreparably damaged.
If not in use, the dryer can be stored in its
packaging in a dust free and protected site at a
maximum temperature of 120°F (50°C), and a
specific humidity not exceeding 90%. Should
the stocking time exceed 12 months, please
contact the manufacturer.
The packaging materials are recyclable. Dispose of material in compliance with the rules
and regulations in force in the destination country.

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2.3 INSTALLATION SITE
Failure to install dryer in the proper ambient conditions will affect the dryer’s ability to condense
refrigerant gas. This can cause higher loads on the compressor, loss of dryer efficiency and
performance, overheated condenser fan motors, electrical component failure and dryer failure due to
the following: compressor loss, fan motor failure and electrical component failure. Failures of this type
will affect warranty considerations.
Do not install dryer in an environment of corrosive chemicals, explosive gasses, poisonous gasses;
steam heat, areas of high ambient conditions or extreme dust and dirt.
In case of fire, use an approved fire
extinguisher, water is not an acceptable
means in cases of fire.
Minimum installation requirements:
•Select a clean dry area, free from dust, and
protected from atmospheric disturbances.
•The supporting area must be smooth, horizontal
and able to hold the weight of the dryer.
•Minimum ambient temperature +34 °F (+1 °C).
•Maximum ambient temperature +120°F (50°C),
•Allow at least a clearance of 40in (1m) on each
side of the dryer for proper ventilation and to
facilitate eventual maintenance operations.
The dryer does not require attachment to the floor
surface; however installations where the unit is
suspended require an attachment to the hanging
apparatus.
40in-1m
40in-1m
40in-1m
40in-1m
20-50
1in-26mm
1/2in - 14mm
3/8in - 10mm
14in - 354mm
LGT0012
1.1/4in
30mm
2.4 INSTALLATION LAYOUT
1Air compressor
2Condensate separator
3Line filter (min. 20 micron)
4By-pass group
5AHT Dryer
Aftercooler
Pre-Filter (FTP Series - 3 micron)
Alu-Dry Module
6Compressed air tank
7Final filter
1
- A -
- B -
2
8
3
8
6
8
8
8
5
5.1
5.2
5.3
IN
OUT
8
7
4
6
8
7
8
2 3
1
8
8
5
8
8
5.3
OUT
5.2
5.1
IN
4
8Condensate drain
In case of heavily polluted inlet air (ISO 8573.1 class 4.-.4 or worse quality), we recommend the additional
installation of a pre-filter (20 micron minimum) to prevent a clogging of the heat exchanger.
Type A installation is suggested when the compressor operates at reduced intermittence and the total consumption
equals the compressor flow rate.
Type B installation is suggested when the air consumption can consistently change with peak values highly exceeding
the flow rate of the compressor. The capacity of the tank must be sized in order to compensate eventual instantaneous
demand conditions (peak air consumption).

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2.5 CORRECTION FACTORS
Correction factor for operating pressure changes :
Inlet air pressure psig
60 80 100 120 140 160 180 200
barg
4 5.5 7 8 10 11 12.5 14
Factor (F1) 0.79 0.91 1.00 1.07 1.13 1.18 1.23 1.27
Correction factor for ambient temperature changes:
Ambient temperature ºF
≤80 90 100 105 110 115 120
ºC
≤27 32 38 40 43 46 50
Factor (F2) 1.22 1.11 1.00 0.94 0.89 0.83 0.78
Correction factor for inlet air temperature changes:
Air temperature ºF
≤140 160 170 180 195 210
ºC
≤60 70 76 82 90 100
Factor (F3) 1.26 1.13 1.07 1.00 0.90 0.81
Correction factor for DewPoint changes:
DewPoint ºF
37 41 45 50
ºC
3 5 7 10
Factor (F4) 0.78 0.90 1.00 1.12
How to find the air flow capacity: How to select a suitable dryer for a given duty:
Air flow
capacity =XFactor (F1)
Factor
(F2)
XFactor
(F3)
X X Factor
(F4)
Nominal
duty
= ÷
Factor
(F1)
Factor
(F2)
÷
Factor
(F3)
÷ ÷
Factor
(F4)
Design
air flow
Std. air
flow rate
Minimum
Example: Example:
An AHT 150 has a nominal duty of 150 scfm
(255 m3/h). What is the maximum allowable flow
through the dryer under the following operating
conditions:
−Inlet air pressure = 120 psig (8 barg)
−Ambient temperature = 105°F (40°C)
−Inlet air temperature = 195°F (90°C)
−Pressure DewPoint = 45°F (7°C)
Each item of data has a corresponding numerical
factor as follows:
The procedure here is to list the operating
conditions and then to locate the corresponding
numerical factors:
−Design air flow = 95 scfm (161 m3/h)
−Inlet air pressure = 120 psig (8 barg)
−Ambient temperature = 105°F (40°C)
−Inlet air temperature = 195°F (90°C)
−Pressure DewPoint = 45°F (7°C)
In order to select the correct dryer model the
required flow rate is to be divided by the correction
factors relating to above mentioned parameters:
= 137 scfm →This is the maximum flow
rate that the dryer can accept under these
operating conditions.
= 104 scfm →Therefore the model suitable
for the conditions above is AHT 150 (150 scfm
or 255 m3/h - nominal duty).
=
x
x
x
x
1.07
150
0.94
1.00
0.90
capacity
Air flow
=
÷
÷
÷
÷
1.07
95
0.94
1.00
0.90
flow rate
Minimum

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2.6 CONNECTION TO THE COMPRESSED AIR SYSTEM
Operations to be performed by qualified personnel only.
Never work on compressed air system under pressure.
The user is responsible to ensure that the dryer will never be operated with pressure exceeding
the maximum pressure rating on the unit data tag.
Over-pressurizing the dryer could be dangerous for both the operator and the unit.
The air temperature and the flow entering the dryer must comply within the limits stated on the identification
plate. The system connecting piping must be kept free from dust, rust, chips and other impurities, and must
be consistent with the flow-rate of the dryer. In case of treatment of air at particularly high temperature, the
installation of a final refrigerator could result necessary. In order to perform maintenance operations, it
recommended that a dryer by-pass system be installed as shown in the following illustration.
Dryer Ø [137-F] A [in - mm]
AHT 20-50 1/2” 3 1/2“ - 90
AHT 75 1” 15 7/8“ - 405
AHT 100-150 1.1/4” 18 11/16“ - 475
AHT 200-250 1.1/2” 23 3/8“ - 565
AHT 300-350 2" 22 3/4“ - 575
In realising the dryer, particular measures have been taken in order to limit the vibration which could occur
during the operation. Therefore we recommend to use connecting pipes able to insulate the dryer from
possible vibrations originating from the line (flexible hoses, vibration damping fittings, etc.).
CAUTION:
PIPING THE DRYER, INLET/OUTLET CONNECTIONS MUST BE SUPPORTED AS
SHOW IN THE DIAGRAM.
FAILING WILL RESULT IN DAMAGE

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2.7 ELECTRICAL CONNECTIONS
Qualified personnel should carry out connecting unit to the main power. Be sure to check the local
codes in your area.
Before connecting the unit to the electrical supply, verify the identification plate for the proper electrical
information. Voltage tolerance is +/- 5%.
Dryer supplied at 115/1/60 voltage comes with a mains connecting cable already installed and ending with a
North-American standard plug 2 poles + ground. Dryer supplied at 230/1/60, voltages comes with a box for
the connection to the mains.
Be sure to provide the proper fuses or breakers based on the data information located on the nameplate.
The mains socket must be provided with a mains magneto-thermal differential breaker (I∆n=0.03A),
adjusted on the basis of the consumption of the dryer (see the nominal values on the data plate of the
dryer). The cross section of the power supply cables must comply with the consumption of the dryer, while
keeping into account also the ambient temperature, the conditions of the mains installation, the length of the
cables, and the requirements enforced by the local Power Provider.
Connect to a properly grounded outlet. Improper connection of the equipment-grounding
conductor can result in risk of electric shock. Do not use adapters on the main socket- if it does
not fit the outlet, have a proper outlet installed by a qualified electrician.
2.8 CONDENSATE DRAIN
The condensate is discharge at the system pressure.
Drain line should be secured.
Never point the condensate drain line towards anybody.
The dryer comes already fitted with two electronically level controlled BEKOMAT condensate drains.
Connect and properly fasten the condensate drain to a collecting plant or container.
The drain cannot be connected to pressurized systems.
Don’t dispose the condensate in the environment.
The condensate collected in the dryer contains oil particles released in the air by the compressor.
Dispose the condensate in compliance with the local rules.
We suggest to install a water-oil separator where to convey all the condensate drain coming from
compressors, dryers, tanks, filters, etc.
3.1 PRELIMINARY OPERATION
Verify that the operating parameters match with the nominal values stated on the identification plate
of the dryer (voltage, frequency, air pressure, air temperature, ambient temperature, etc.).
This dryer has been thoroughly tested, packaged and inspected prior to shipment. Nevertheless, the unit
could be damaged during transportation, check the integrity of the dryer during first start-up and monitor
operation during the first hours of operation.
Qualified personnel must perform the first start-up.
When installing and operating this equipment, comply with all National Electrical Code and any
applicable federal, state and local codes.
Who is operating the unit is responsible for the proper and safe operation of the dryer.
Never operate equipment with panels removed.

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3.2 FIRST START-UP
This procedure should be followed on first start-up, after periods of extended shutdown or
following maintenance procedures.
Qualified personnel must perform the start-up.
Sequence of operations (refer to paragraph 5.1 Control Panel) :
•Ensure that all the steps of the “Installation” chapter have been observed.
•Ensure that the connection to the compressed air system is correct and that the piping is suitably fixed
and supported.
•Ensure that the condensate drain pipe is properly fastened and connected to a collection system or
container.
•Ensure that the by-pass system (if installed) is open and the dryer is isolated
•Ensure that the manual valve of the condensate drain circuit is open.
•Remove any packaging and other material which could obstruct the area around the dryer.
•Activate the mains switch.
•Switch on the dryer by closing the main switch on the control panel (pos. 1).
•Ensure that DMC14 electronic instrument is ON.
•Ensure the consumption matches with the values of the data plate.
•Ensure the fan work properly - wait for its first interventions.
•Allow the dryer temperature to stabilise at the pre-set value.
•Slowly open the air inlet valve.
•Slowly open the air outlet valve.
•Slowly close the central by-pass valve of the system (if installed).
•Check the piping for air leakage.
•Ensure the drain is regularly cycling - wait for its first interventions.
3.3 START-UP AND SHUT DOWN
Start-up (refer to paragraph 5.1 Control Panel) :
•Check the condenser for cleanliness.
•Verify that the system is powered.
•Switch on the dryer by closing the main switch on the control panel (pos. 1).
•Ensure that DMC14 electronic instrument is ON.
•Wait a few minutes; verify that the DewPoint temperature displayed on electronic instrument DMC14 is
correct and that the condensate is regularly drained.
•Switch on the air compressor.
Shut down (refer to paragraph 5.1 Control Panel) :
•Verify that the DewPoint temperature displayed on electronic controller DMC14 is correct.
•Shut down the air compressor.
•After a few minutes, Shut down the dryer using the main switch on the control panel (pos. 1).
NOTE : A DewPoint within 32°F (0°C) and +60°F (15°C) displayed on DMC14 is correct according to the
possible working conditions (flow-rate, temperature of the incoming air, ambient temperature, etc.).
During the operation, the refrigerating compressor will run continuously. The dryer must remain on during
the full usage period of the compressed air, even if the air compressor works intermittently.
The number of starts must be no more than 6 per hour. The dryer must stop running for at
least 5 minutes before being started up again.
The user is responsible for compliance with these rules. Frequent starts may cause
irreparable damage.

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4.1 TECHNICAL SPECIFICATIONS AHT 20-150 -1 (115/1/60)
150 150 255
4245
5.0 - 0.35
R404A
20.1/2 - 0.58
1500 - 880
FTP 055
1/2
8500 1100
10.1
1350
12.2
146 - 66
100 100 170
2830
3.0 - 0.21
1.1/4”
16 - 0.45
1000 - 590
880
8.7
1020
11.2
134 - 61
75 75
127
2123
200 - 14
3.8 - 0.26
1”
14 - 0.40
900 - 530
FTP 030
1/3+
6200
770
8.3
890
8.9
110 - 50
50 50 85
1415
4.1 - 0.28
10.1/4 - 0.29
1/5+
3600
460
4.7
510
5.1
73 - 33
40 40 68
1132
2.9 - 0.20
FTP 012
1/6
2500
310
3.1
360
3.9
71 - 32
30 30 51
849
2.8 - 0.19
8 - 0.22
1/8
2100
280
2.5
320
3.0
68 - 31
- 1 (115/1/60)
20 20 34
566
≤45 - ≤7
100 (120) - 38 (50)
34 - 1
180 (210) - 82 (100)
100 - 7
200 - 16
1.5 - 0.10
1/2”
R134.a
7 - 0.20
500 - 290
FTP 008
1/10
1680
115/1/60
210
2.3
240
2.7
< 70
66 - 30
[scfm]
[m3/h]
[l/min]
[°F – °C] [°F – °C] [°F – °C] [°F – °C]
[psig – barg] [psig – barg]
[psi – bar]
[NPT-F]
[oz – kg]
[cfm – m3/h]
[model]
[Btu/h]
[Ph/V/Hz]
[W]
[A]
[W]
[A]
[dbA]
[lbs – kg]
AHT MODEL
Air flow rate at nominal condition 1
Pressure DewPoint at nominal condition 1
Nominal (max.) ambient temperature Min. ambient temperature Nominal (max.) inlet air temperature Nominal inlet air pressure Max. inlet air pressure Air pressure drop - ∆p Inlet - Outlet connections Refrigerant type Refrigerant quantity 2
Cooling air flow Pre-Filter (3 micron) Nominal refrigerating compressor power Heat load Standard Power Supply 2
Nominal electric absorption Max. electric absorption Max. level noise at 40 in (1m) Weight
1The nominal condition refers to an ambient temperature of 100°F (38°C) with inlet air at 100psig (7barg) and 100°F (38°C).
2Check the data shown on the identification plate.

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4.2 TECHNICAL SPECIFICATIONS AHT 20-350 -2 (230/1/60)
350 350 594
9905
4.5 - 0.31
50 – 1.40
6350 - 3700
FTP 120
2700
12.8
3420
15.6
304 - 138
300 300 509
8490
4.1 - 0.28
2”
44 – 1.25
6150 - 3600
1.1/4
20400
2600
12.1
3300
15.0
291 - 132
250 250 425
7075
5.1 - 0.35 33.1/2 - 0.95
5000 - 2900
1.1/8
FTP 080
17500
1820
8.1
2280
10.4
185 - 84
200 200 340
5660
3.3 - 0.23
1.1/2”
30.1/2 - 0.87
3500 - 2060
5/8
11900
1550
7.0
1650
7.3
165 - 75
150 150 255
4245
5.0 -0.35
R404A
20.1/2- 0.58
1500 - 880
1/2
FTP 055
8500 1100
5.1
1350
6.1
146 - 66
100 100 170
2830
3.0 - 0.21
1.1/4”
16 - 0.45
1000 - 590
880
4.3
1020
5.6
134 - 61
75 75
127
2123
200 - 14
3.8 - 0.26
1”
14 - 0.40
900 - 530
1/3+
FTP 030
6200
770
4.2
890
4.5
110 - 50
50 50 85
1415
4.1 - 0.28
10.1/4 – 0.29
1/4
4000
460
2.3
510
2.5
73 - 33
40 40 68
1132
2.9 - 0.20
FTP 012
310
1.6
360
1.9
71- 32
30 30 51
849
2.8 - 0.19
8 - 0.22
1/6
2500
280
1.3
320
1.5
68 - 31
- 2 (230/1/60)
20 20 34
566
≤45 - ≤7
100 (120) - 38 (50)
34 - 1
180 (210) - 82 (100)
100 - 7
230 - 16
1.5 - 0.10
1/2”
R134.a
7- 0.20
500 - 290
1/10
FTP 008
1680
230/1/60
210
1.1
240
1.4
< 70
66 - 30
[scfm]
[m3/h]
[l/min]
[°F – °C] [°F – °C] [°F – °C] [°F – °C]
[psig – barg] [psig – barg]
[psi – bar]
[NPT-F]
[oz – kg]
[cfm – m3/h]
[model]
[Btu/h]
[Ph/V/Hz]
[W]
[A]
[W]
[A]
[dbA]
[lbs – kg]
AHT MODEL
Air flow rate at nominal condition 1
Pressure DewPoint at nominal condition 1
Nominal (max.) ambient temperature Min. ambient temperature Nominal (max.) inlet air temperature Nominal inlet air pressure Max. inlet air pressure Air pressure drop - ∆p Inlet - Outlet connections Refrigerant type Refrigerant quantity 2
Cooling air flow Nominal refrigerating compressor power Pre-Filter (3 micron) Heat load Standard Power Supply 2
Nominal electric absorption Max. electric absorption Max. level noise at 40 in (1m) Weight
1The nominal condition refers to an ambient temperature of 100°F (38°C) with inlet air at 100psig (7barg) and 100°F (38°C).
2Check the data shown on the identification plate.

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5.1 CONTROL PANEL
The control panel illustrated below is the only dryer-operator interface.
AHT 20 - 75
K
1
2 3
PQS0003
DMC14
1
0
AHT 100 - 350
K
I
ON
1 3
set
DMC 14
°C
esc
°F
2
PQS0004
1
Main switch 3
Air and refrigerating gas flow diagram
2
Electronic control instrument DMC14
5.2 OPERATION
Operating principal – The dryer models described in this manual all operate on the same principal. First the very hot
moisture laden air directly from the compressor enters the aftercooler (copper tube / aluminum fin cooling surface)
where it is cooled to within 18-20°F (10-12°C) of the ambient air temperature. It leaves the aftercooler with entrained
condensed water droplets which are separated by the 3 micron FTP bulk liquid filter separator element and drained
away by the first drain system. The partially cooled moisture laden air next enters an air to air heat exchanger to pre-cool
it. The compressed air next goes through the evaporator, also known as the air to refrigerant heat exchanger. The
compressed air temperature is reduced to approximately 41°F (5°C), causing additional water vapor to condense to
liquid. The liquid is continuously coalesced and collected in the dryer separator for automatic removal by the second
condensate drain. The cool moisture free compressed air then passes back through the air to air heat exchanger to be
reheated to within the ambient temperature as it exits the dryer.
Refrigerant circuit - Refrigerant gas is cycled through the compressor and exits at high pressure to a condenser
where heat is removed causing the refrigerant to condense to a high-pressure liquid state. The liquid is forced
through a capillary tube where the resulting pressure drop allows the refrigerant to boil off at a predetermined
temperature. Low-pressure liquid refrigerant enters the heat exchanger where heat from the incoming air is
transferred causing the refrigerant to boil; the resulting phase change produces a low pressure, low temperature
gas. The low-pressure gas is returned to the compressor, where it is re-compressed and begins the cycle again.
During those periods when the compressed air load is reduced the excess refrigerant is by-passed automatically
back to the compressor via the Hot Gas By-pass Valve circuit.

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5.3 FLOW DIAGRAM (Air-Cooled)
13
1
12
1c
T1
1b
1a
PB
3 54
P
11 10
7
6
TS
9 M
8
PVA
2
DGF0035
21
28
27
21
26
1
Alu-Dry Module 9
Condenser fan
a - Air-to-air heat exchanger 10
Filter Drier
b - Air-to-refrigerant exchanger 11
Capillary tube
c - Condensate separator 12
T1 Temperature probe (DewPoint)
2
Refrigerant pressure-switch P
B
(AHT 300-350) 13
Condensate drain isolation valve
3
Safety thermo-switch T
S
(AHT 125-350)
…
4
Refrigerant pressure-switch P
A
(AHT 300-350)
21
Bekomat drainer
5
Refrigerant Fan pressure-switch P
V
…
6
Refrigerating compressor
26
Aftercooler
7
Hot Gas By-pass Valve 27
Aftercooler fan (AHT 75-350)
8
Condenser (Air-Cooled) 28
Pre-Filter (3 micron)
Compressed air flow direction
Refrigerating gas flow direction
5.4 REFRIGERATING COMPRESSOR
The refrigerating compressor is the pump in the system, gas coming from the evaporator (low pressure side) is
compressed up to the condensation pressure (high pressure side). The compressors utilized are manufactured by
leading manufacturers and are designed for applications where high compression ratios and wide temperature
changes are present.
The hermetically sealed construction is perfectly gas tight, ensuring high-energy efficiency and long, useful
life. Dumping springs support the pumping unit in order to reduce the acoustic emission and the vibration
diffusion. The aspirated refrigerating gas, flowing through the coils before reaching the compression
cylinders cools the electric motor. The thermal protection protects the compressor from over heating and
over currents. The protection is automatically restored as soon as the nominal temperature conditions are
reached.

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5.5 CONDENSER
The condenser is the component in which the gas coming from the compressor is cooled down and
condensed becoming a liquid. Mechanically, a serpentine copper tubing circuit (with the gas flowing inside)
is encapsulated in an aluminum fin package.
The cooling operation occurs via a high efficiency fan, creating airflow within the dryer, moving air through
the fin package. It’s mandatory that the ambient air temperature does not exceed the nominal values. It is
also important TO KEEP THE CONDENSER UNIT FREE FROM DUST AND OTHER IMPURITIES
5.6 FILTER DRIER
Traces of humidity and slag can accumulate inside the refrigerating circuit. Long periods of use can also
produce sludge. This can limit the lubrication efficiency of the compressor and clog the expansion valve or
capillary tube. The function of the Filter Drier, located before the capillary tubing, is to eliminate any
impurities from circulating through the system.
5.7 AFTERCOOLER
The aftercooler is the element where the incoming hot air undergoes the cooling stage. Mechanically, it is
formed by a copper tubing circuit (with the compressed air flowing inside) immersed in an aluminium blades
package. The cooling operation occurs via a high efficiency axial ventilator which, in applying pressure on
the air contained within the dryer, forces it into the blades package. In models AHT 20-50 the aftercooler is
combined with the dryer’s condenser, thus forming just one heat exchanger battery, cooled by just one high
efficiency axial fan.
It is mandatory that the temperature of the ambient air will not exceed the nominal values of the dryer. It is
important TO KEEP THE UNIT FREE FROM DUST AND OTHER IMPURITIES taken in by the fan.
5.8 PRE-FILTER (FTP Series - 3 micron)
Positioned at the outlet of the aftercooler, it assures a good air cleanliness level, in addition to the complete
removal of the water condensed in the aftercooler. REPLACE THE FILTERING ELEMENT (CARTRIDGE)
AT LEAST EVERY 12 MONTHS.
5.9 CAPILLARY TUBE
It consists of a piece of reduced cross section copper tubing located between the condenser and the
evaporator to form a throttling against the flow of the refrigerating fluid. This throttling creates a pressure
drop, which is a function of the temperature to be reached within the evaporator: the lower the capillary tube
outlet pressure, the lower the evaporation temperature. The length and the diameter of the capillary tubing
are accurately sized with the performance to be reached by the dryer; no maintenance/adjustment
operations are necessary.
5.10 ALU-DRY MODULE
The air-to-air and the air-to-refrigerant heat exchangers plus the demister type condensate separator are
housed in a unique module.
The counter-flows of compressed air in the air-to-air heat exchanger ensure maximum heat transfer. The large
cross section of flow channels within the heat exchanger module leads to low velocities and reduced power
requirements. The air-to-refrigerant exchanger, with counter-current flows, assure excellent performances.
The generous dimensions of the exchange surface determines the correct and complete evaporation of the
refrigerant (preventing liquid returning to the compressor). The high efficiency condensate separator is located
within the drying module. No maintenance is required and it offers the additional advantage of creating a cold
coalescing effect for excellent air drying results. The generous collection volume assures the correct operation
of the dryer even with extremely damp inlet air.

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5.11 HOT GAS BY-PASS VALVE
This valve injects part of the hot gas (taken from the discharge side of the compressor) in the pipe between the evaporator
and the suction side of the compressor, keeping the evaporation temperature/pressure constant at approx. 36°F (+2 °C).
This injection prevents the formation of ice inside the dryer evaporator at every load condition.
A
4 mm
5/32 in.
+
-
ADJUSTMENT
The hot gas by-pass valve is adjusted during the manufacturing
testing phase. As a rule no adjustment is required; anyway if it is
necessary the operation must be carried out by an experienced
refrigeration engineer.
WARNING : the use of ¼” Schrader service valves must be
justified by a real malfunction of the refrigeration system. Each
time a pressure gauge is connected, a part of refrigerant is
exhausted.
Without compressed air flow through the dryer, rotate the adjusting screw
(position A on the drawing) until the following value is reached:
Hot gas setting (R134.a) : temperature 33°F (+1 / -0 °F)
pressure 29 psig (+1.5 / -0 psi)
temperature 0.5°C (+0.5 / -0 °K)
pressure 2.0 barg (+0.1 / -0 bar)
Hot gas setting (R404A) : temperature 33°F (+1 / -0 °F)
pressure 75.4 psig (+1.5 / -0 psi)
temperature 0.5 °C (+0.5 / -0 °K)
pressure 5.2 barg (+0.1 / -0 bar)
5.12 REFRIGERANT PRESSURE SWITCHES PA- PB- PV
As operation safety and protection of the dryer a series of pressure switches are installed in gas circuit.
PB :
Low-pressure controller device on the pushing side (carter) of the compressor, is enabled only if the pressure drops
below the pre-set value. The values are automatically reset when the nominal conditions are restored.
Calibrated pressure : R 404 A Stop 14.5 psig - Restart 72.5 psig
R 404 A Stop 1.0 barg - Restart 5.0 barg
PA :
This high-pressure controller device, located on the pushing side on the compressor, is activated when the
pressure exceeds the pre-set value. It features a manual-resetting button mounted on the controller itself.
Calibrated pressure : R 404 A Stop 464 psig - Manual reset
R 404 A Stop 32 barg - Manual reset
PV :
Fan control pressure switch is placed at the discharge side of refrigeration compressor. It keeps the
condensation temperature/pressure constant within preset limits (Air-Cooled).
Calibrated pressure : R 134.a Start 160 psig (117°F) - Stop 116 psig (97°F) - Tolerance ±15 psi
R 134.a Start 11 barg (47°C) - Stop 8 barg (36°C) - Tolerance ±1 bar
R 404 A Start 290 psig (113°F) - Stop 232 psig (97°F) - Tolerance ±15 psi
R 404 A Start 20 barg (45°C) - Stop 16 barg (36°C) - Tolerance ±1 bar
5.13 SAFETY THERMO-SWITCH TS
To protect the operating safety and the integrity of the dryer, a thermo-switch
(TS) is installed on the refrigerant gas circuit. The thermo-switch sensor, in
case of unusual discharge temperatures, stops the refrigerating compressor
before it is permanently damaged.
1
2
PQS0005
TS:
Manually reset the thermo-switch only after the nominal operating
conditions have been restored. Unscrew the relative cap (see pos.1 in
the figure) and press the reset button (see pos.2 in the figure).

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5.14 DMC14 ELECTRONIC INSTRUMENT (AIR DRYER CONTROLLER)
set
Button
-
access the set-up.
esc
Button
-
Exit programming / decrease value.
Button
-
Value increment.
LED -
Dryer in alarm status.
●°C
LED -
Display the set temperature scale (°C).
●°F
LED -
Display the set temperature scale (°F).
DMC 14
°C
°F
escset
DISPLAY
PQS0006
●
LED -
Not used
Through the digital thermometer with an alphanumerical display, the DMC14 controller shows the DewPoint
detected by the probe in the evaporator.
The LED shows any alarm condition, it can happen when :
- pressure DewPoint is too high;
- pressure DewPoint is too low;
- the probe is faulty.
If the probe is faulty, the instrument also shows “PF” message (Probe Failure), and alarm activation is immediate. In
case of “DewPoint too low” condition (ASL parameter, that is fix and equal to 28.5°F or -2°C), the alarm signal is
delayed of a fix time (AdL parameter) equal to 30 sec, while for “DewPoint too high” condition the value (ASH
parameter) is set by the user and the signal is activated with AdH delay time, that can be also set up by the operator
(the instrument is already adjusted during final test of the dryer, please see following values). When DewPoint
returns into operating temperature (set range), the alarm condition is deactivated.
DMC14 allows also remote annunciation of the alarm condition of the dryer; this through a volt free contact on
terminals 8 & 9 - please also see electric drawings into the attachments (max 250V 1A, min 5VDC 10mA)
- with dryer off or in alarm conditions contact is open
- with dryer on and correct operating DewPoint, contact is closed.
OPERATION - After dryer starting, the electronic controller displays current operating DewPoint : it shows
the measured temperature in Celsius degrees ( ● °C) with a 0.5°C resolution, or in Fahrenheit degrees ( ●
°F) with a 1°F resolution.
SET-UP (PROGRAMMING)
To access the set-up, keep pressed simultaneously both
set
and button for at least 5 seconds. In
this way programming operation will be activated and the controller display shows the first parameter
that can be set (Ton). After that, by pressing
set
buttom the display shows the value set for that parameter.
If the value is correct press
set
button to conferm it and to give access on following parameters. To
change the value of selected parameter, must be used
esc
and button, respectively to decrease or
increase the value. All parameters that can be modified are indicated in following table :
Display Description Value range
Set value
Equal to
Ton Not used 01 … 20 02 2 sec
ToF Not used 01 … 20 01 1 min
ASH Alarm threshold for a high DewPoint . 0.0 … 68.0 60 60°F
AdH ASH alarm time before signal 00 … 20 20 20 min
SCL Temperature scale °C … °F °F ° Fahrenheit
Fixed parameters :
ASL (low DewPoint alarm) = -2°C or 28.5°F AdL (signal delay) = 30 sec
It is possibile to exit from set-up conditon in any moment, by pressing simultaneously both
esc
and button.
If any operations are not made during 30 seconds, the controller exits automatically from programming operation.

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5.15 ELECTRONIC LEVEL CONTROLLED CONDENSATE DRAIN BEKOMAT 31
The electronic level controlled drain BEKOMAT has a special condensate management that makes sure that
condensate is drained safely without any unnecessary air-loss. This drain consists of a condensate accumulator
where a capacitive sensor continuously checking liquid level is placed: as soon as the accumulator is filled, the
sensor passes a signal to the electronic control and a diaphragm solenoid valve will open to discharge the
condensate. Right in time the discharge line will be closed again without wasting compressed air.
ATTENTION! These BEKOMAT condensate drains have been specially designed for the use in a
refrigerant dryer AHT. Any Installation in other compressed air treatment units or the exchange against a
different drain brand may lead to malfunction. Do not exceed the max. operating pressure (see type plate)!
MAKE SURE WHEN THE DRYER STARTS THE UPSTREAM VALVE IS OPEN.
CONTROL PANEL FOR BEKOMAT 31 AHT 20-100
TEST
Power
The control panel here illustrated allows checking of drain working.
Power-LED ON - drain ready to work / supplied
Test : test button - discharge test (keep pushed for 2 seconds)
MEMBRANE FUNCTION OF BEKOMAT 31 AHT 20-100
TROUBLESHOOTING BEKOMAT 31 AHT 20-100
The detection of defects should be carried out by qualified personnel.
SYMPTOM POSSIBLE CAUSE - SUGGESTED ACTION
No led lighting up. 
Check for mains failure.
 Verify the electric wiring (internal and/or external).
 Check internal printed circuit board for possible damage.
Pressing of Test
button, but no
condensate discharge.
 The service valve located before the drain is closed - open it.
 The dryer is not under pressure - restore nominal condition.
 Solenoid valve defective. Replace Service Unit (see para 5.17 MAINTENANCE
BEKOMAT).
 The internal printed circuit board is damaged - replace the drain.
Condensate discharge
only when Test button
is pressed.
 Too much internal dirt. Replace Service Unit (see para 5.17 MAINTENANCE
BEKOMAT).
Drain keeps blowing
off air.
 Replace Service Unit (see para 5.17 MAINTENANCE BEKOMAT).
Drain in alarm
condition.
 The service valve located before the drain is closed - open it.
 The dryer is not under pressure - restore nominal condition.
 Replace service unit (see para 5.17 MAINTENANCE BEKOMAT).

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5.16 ELECTRONIC LEVEL CONTROLLED CONDENSATE DRAIN BEKOMAT 32
The electronic level controlled drain BEKOMAT has a special condensate management that makes sure that
condensate is drained safely without any unnecessary air-loss. This drain consists of a condensate accumulator
where a capacitive sensor continuously checking liquid level is placed: as soon as the accumulator is filled, the
sensor passes a signal to the electronic control and a diaphragm solenoid valve will open to discharge the
condensate. Right in time the discharge line will be closed again without wasting compressed air.
ATTENTION! These BEKOMAT condensate drains have been specially designed for the use in a refrigerant
dryer AHT. Any installation in other compressed air treatment units or the exchange against a different drain
brand may lead to malfunction. Do not exceed the max. operating pressure (see type plate)!
MAKE SURE WHEN THE DRYER STARTS THE UPSTREAM VALVE IS OPEN.
CONTROL PANEL FOR BEKOMAT 32 AHT 150-350
The control panel here illustrated allows checking of drain working.
Power-LED ON - drain ready to work / supplied
Test : test button - discharge test (keep pushed for 2 seconds)
Malfunction/Alarm
Test : button - discharge test (keep pushed for 2 seconds)
The BEKOMAT 32 also has an alarm mode function:
If normal conditions have not been restored after 1 minute, a fault signal will be triggered:
• Alarm LED flashes.
• Alarm signal switches over (can be transmitted via potential-free contact terminals 2.2, 2.3, 2.4).
• Valve opens every 4 minutes for a period of 7.5 seconds.
Once the fault is cleared, the BEKOMAT will automatically switch back to the normal mode of operation.