ESAB LAF 1251 User manual

Instruction manual
0449 505 101 GB 20230412 Valid for: serial no. 126-xxx-xxxx
LAF 1251 / LAF 1251M

TABLE OF CONTENTS
0449 505 101 © ESAB AB 2023
1SAFETY ....................................................................................................... 4
1.1 Meaning of symbols ............................................................................... 4
1.2 Safety precautions ................................................................................. 4
2INTRODUCTION.......................................................................................... 8
3TECHNICAL DATA ...................................................................................... 9
4INSTALLATION............................................................................................ 10
4.1 Location................................................................................................... 10
4.2 Connections............................................................................................ 11
5OPERATION ................................................................................................ 12
5.1 Controls................................................................................................... 12
6MAINTENANCE........................................................................................... 13
6.1 Cleaning .................................................................................................. 13
6.1.1 Welding power source.......................................................................... 13
6.1.2 Contactor.............................................................................................. 13
7ORDERING SPARE PARTS ........................................................................ 14
DIAGRAM ............................................................................................................ 15
CONNECTION INSTRUCTION............................................................................ 19
ORDERING NUMBERS....................................................................................... 21
Rights reserved to alter specifications without notice.

1 SAFETY
0449 505 101 -4- © ESAB AB 2023
1 SAFETY
1.1 Meaning of symbols
As used throughout this manual: Means Attention! Be Alert!
DANGER!
Means immediate hazards which, if not avoided, will result in immediate,
serious personal injury or loss of life.
WARNING!
Means potential hazards which could result in personal injury or loss of life.
CAUTION!
Means hazards which could result in minor personal injury.
WARNING!
Before use, read and understand the instruction manual
and follow all labels, employer´s safety practices and
Safety Data Sheets (SDSs).
1.2 Safety precautions
Users of ESAB equipment have the ultimate responsibility for ensuring that anyone who
works on or near the equipment observes all the relevant safety precautions. Safety
precautions must meet the requirements that apply to this type of equipment. The following
recommendations should be observed in addition to the standard regulations that apply to
the workplace.
All work must be carried out by trained personnel well-acquainted with the operation of the
equipment. Incorrect operation of the equipment may lead to hazardous situations which can
result in injury to the operator and damage to the equipment.
1. Anyone who uses the equipment must be familiar with:
○ its operation
○ location of emergency stops
○ its function
○ relevant safety precautions
○ welding and cutting or other applicable operation of the equipment
2. The operator must ensure that:
○ no unauthorised person is stationed within the working area of the equipment
when it is started up
○ no-one is unprotected when the arc is struck or work is started with the
equipment
3. The workplace must:
○ be suitable for the purpose
○ be free from drafts

1 SAFETY
0449 505 101 -5- © ESAB AB 2023
4. Personal safety equipment:
○ Always wear recommended personal safety equipment, such as safety glasses,
flame-proof clothing, safety gloves
○ Do not wear loose-fitting items, such as scarves, bracelets, rings, etc., which
could become trapped or cause burns
5. General precautions:
○ Make sure the return cable is connected securely
○ Work on high voltage equipment may only be carried out by a qualified
electrician
○ Appropriate fire extinguishing equipment must be clearly marked and close at
hand
○ Lubrication and maintenance must not be carried out on the equipment during
operation
WARNING!
Arc welding and cutting can be injurious to yourself and others. Take precautions
when welding and cutting.
ELECTRIC SHOCK - Can kill
• Install and ground the unit in accordance with instruction manual.
• Do not touch live electrical parts or electrodes with bare skin, wet gloves or
wet clothing.
• Insulate yourself from work and ground.
• Ensure your working position is safe
ELECTRIC AND MAGNETIC FIELDS - Can be dangerous to health
• Welders having pacemakers should consult their physician before welding.
EMF may interfere with some pacemakers.
• Exposure to EMF may have other health effects which are unknown.
• Welders should use the following procedures to minimize exposure to
EMF:
○ Route the electrode and work cables together on the same side of
your body. Secure them with tape when possible. Do not place your
body between the torch and work cables. Never coil the torch or work
cable around your body. Keep welding power source and cables as
far away from your body as possible.
○ Connect the work cable to the workpiece as close as possible to the
area being welded.
FUMES AND GASES - Can be dangerous to health
• Keep your head out of the fumes.
• Use ventilation, extraction at the arc, or both, to take fumes and gases
away from your breathing zone and the general area.
ARC RAYS - Can injure eyes and burn skin
• Protect your eyes and body. Use the correct welding screen and filter lens
and wear protective clothing.
• Protect bystanders with suitable screens or curtains.
NOISE - Excessive noise can damage hearing
Protect your ears. Use earmuffs or other hearing protection.

1 SAFETY
0449 505 101 -6- © ESAB AB 2023
MOVING PARTS - Can cause injuries
• Keep all doors, panels and covers closed and securely in place. Have only
qualified people remove covers for maintenance and troubleshooting as
necessary. Reinstall panels or covers and close doors when service is
finished and before starting engine.
• Stop engine before installing or connecting unit.
• Keep hands, hair, loose clothing and tools away from moving parts.
FIRE HAZARD
• Sparks (spatter) can cause fire. Make sure that there are no inflammable
materials nearby.
• Do not use on closed containers.
HOT SURFACE - Parts can burn
• Do not touch parts bare handed.
• Allow cooling period before working on equipment.
• To handle hot parts, use proper tools and/or insulated welding gloves to
prevent burns.
MALFUNCTION - Call for expert assistance in the event of malfunction.
PROTECT YOURSELF AND OTHERS!
CAUTION!
This product is solely intended for arc welding.
WARNING!
Do not use the power source for thawing frozen pipes.
CAUTION!
Class A equipment is not intended for use in residential
locations where the electrical power is provided by the
public low-voltage supply system. There may be
potential difficulties in ensuring electromagnetic
compatibility of class A equipment in those locations,
due to conducted as well as radiated disturbances.

1 SAFETY
0449 505 101 -7- © ESAB AB 2023
NOTE!
Dispose of electronic equipment at the recycling
facility!
In observance of European Directive 2012/19/EC on
Waste Electrical and Electronic Equipment and its
implementation in accordance with national law,
electrical and/or electronic equipment that has reached
the end of its life must be disposed of at a recycling
facility.
As the person responsible for the equipment, it is your
responsibility to obtain information on approved
collection stations.
For further information contact the nearest ESAB dealer.
ESAB has an assortment of welding accessories and personal protection equipment
for purchase. For ordering information contact your local ESAB dealer or visit us on
our website.

2 INTRODUCTION
0449 505 101 -8- © ESAB AB 2023
2 INTRODUCTION
LAF 1251 / LAF 1251M are remote-controlled 3-phase welding power sources designed for
high-efficiency mechanical submerged-arc welding (SAW).
The welding power sources are fan-cooled and are monitored by a thermal cutout against
overload. When the thermal cutout is deployed the yellow lamp on the front panel illuminates
automatically. The reset is carried out automatically when the temperature has decreased to
a permitted level.

3 TECHNICAL DATA
0449 505 101 -9- © ESAB AB 2023
3 TECHNICAL DATA
LAF 1251 LAF 1251M
Mains connection 380/400/415/500 V, 3~50 Hz 220/230/400/415/500 V, 3~50 Hz
440/550 V, 3~60 Hz 230/400/440/550 V, 3~60 Hz
Primary current Imax 104 A Imax 171 A
Permissible load at:
100 % duty cycle 1250 A / 44 V 1250 A / 44 V
Setting range 100-1250 A / 24-44 V 100-1250 A / 24-44 V
No-load voltage 53 V 53 V
No-load power 210 W 210 W
Efficiency at max current 89 % 88 %
Power factor at max
current 0.89 0,94
Apparent power at max
current 69 kVA
Active power at max
current 61.7 kW
Operating temperature -10 to +40 °C
Continual sound pressure
at no-load <70 dB(A)
Weight 490 kg 490 kg
Dimensions L × W × H 774 × 598 × 1430 mm 774 × 598 × 1430 mm
Insulation class
(transformer) H H
Enclosure class IP 23 IP 23
Application class
Enclosure class
The IP code indicates the enclosure class, i.e. the degree of protection against penetration
by solid objects or water.
Equipment marked IP23 is intended for indoor and outdoor use.
Application class
The symbol indicates that the power source is designed for use in areas with increased
electrical hazard.

4 INSTALLATION
0449 505 101 - 10 - © ESAB AB 2023
4 INSTALLATION
The installation must be carried out by a professional.
NOTE!
Mains supply requirements
High power equipment may, due to the primary current drawn from the mains
supply, influence the power quality of the grid. Therefore connection restrictions or
requirements regarding the maximum permissible mains impedance or the required
minimum supply capacity at the interface point to the public grid may apply for some
types of equipment (see "TECHNICAL DATA" chapter). In this case it is the
responsibility of the installer or user of the equipment to ensure, by consultation with
the distrubution network operator if necessary, that the equipment may be
connected.
4.1 Location
WARNING!
Secure the equipment - particularly if the ground is uneven or sloping.
• Place the welding power source on a level foundation.
• Make sure there is nothing to prevent the cooling.
Lifting instructions

4 INSTALLATION
0449 505 101 - 11 - © ESAB AB 2023
4.2 Connections
• On delivery the welding power source is connected
for 400 V.
• For other supply voltage:
Remove the left side plate.
Perform the switchings on the main and control
transformer in accordance with the connection
instruction in "CONNECTION INSTRUCTION"
chapter.
• Select the mains cable with the correct cable area
and fuse the cable with the correct fuse in
accordance with local regulations (see the table
below in "Mains connection" section).
• Remove the front plates (× 2).
•Connect the ground cable to the screw marked .
• Tighten the cable clamp (1).
• Connect the mains cables to the main connection terminals L1, L2 and L3 (5).
• Connect the control cable between the welding power source and the control box to
the 28-pin connector (2) on the inside of the welding power source.
• Connect the 1-pin measuring cable (4) for measuring the arc voltage to the return
cable/welding head.
• Connect a suitable welding and return cable in the connectors (3) marked + and - on
the front of the welding power source.
• Fit the side/front plates.
Mains connection
LAF 1251 50 Hz 60 Hz
Voltage (V) 380 400 / 415 500 440 550
Phase current I1eff (A) 104 99 80 99 80
Cable area (mm2)3×35 + 25 3×35 + 25 3×25 + 16 3×35 + 25 3×25 + 16
Fuse, slow (A) 120 100 80 100 80
LAF 1251M 50 Hz 60 Hz
Voltage (V) 230 400 / 415 500 230 400 / 440 550
Phase current I1eff (A) 171 99 80 171 99 80
Cable area (mm2)3×70 + 35 3×35 + 25 3×25 + 16 3×70 + 35 3×35 + 25 3×25 + 16
Fuse, slow (A) 160 100 80 160 100 80
NOTE!
The mains cable areas and fuse sizes as shown above are in accordance with
Swedish regulations. For other regions, supply cables must be suitable for the
application and meet local and national regulations.

5 OPERATION
0449 505 101 - 12 - © ESAB AB 2023
5 OPERATION
General safety regulations for handling the equipment can be found in the "SAFETY"
chapter of this manual. Read it through before you start using the equipment!
NOTE!
Never use the welding power source without side plates.
NOTE!
The power source must be set to analogue mode to use the PEI control unit.
5.1 Controls
The front panel contains:
1. Main circuit-breaker for switching the mains voltage and the fan on and off in
the welding power source.
• Position "1" On
• Position "0" Off
2. • The indicator lamp (white) illuminates when the main switch is switched
on.
3. Indicator lamp for overheating (yellow)
• The indicator lamp illuminates when the thermal cutout is deployed due
to excess temperature in the welding power source.
• The indicator lamp goes out when the temperature in the welding
power source has decreased to a permitted level.
4. Pushbutton resetting the automatic fuse FU2 for 42 V supply voltage.

6 MAINTENANCE
0449 505 101 - 13 - © ESAB AB 2023
6 MAINTENANCE
CAUTION!
All warranty undertakings from the supplier cease to apply if the customer attempts
any work to rectify any faults in the product during the warranty period.
6.1 Cleaning
6.1.1 Welding power source
WARNING!
Blocked air inlets or outlets will lead to overheating.
• Clean the welding power source as necessary.
Dry compressed air is recommended for the purpose.
6.1.2 Contactor
WARNING!
Never use compressed air to clean the contactor without first taking it apart
completely.
NOTE!
To ensure the reliable operation of the contactor, the magnetic parts must be kept
clean.
If the contactor has to be cleaned it must be taken apart, and all the pieces be
cleaned.
Alternatively, the contactor can be replaced.

7 ORDERING SPARE PARTS
0449 505 101 - 14 - © ESAB AB 2023
7 ORDERING SPARE PARTS
CAUTION!
Repair and electrical work should be performed by an authorised ESAB service
technician. Use only ESAB original spare and wear parts.
LAF 1251 / LAF 1251M is designed and tested in accordance with the international and
European standards IEC-/EN60974-1 and IEC-EN60974-10. It is the obligation of the
service unit which has carried out the service or repair work to make sure that the product
still conforms to the said standard.
Spare parts and wear parts can be ordered through your nearest ESAB dealer, see
esab.com. When ordering, please state product type, serial number, designation and spare
part number in accordance with the spare parts list. This facilitates dispatch and ensures
correct delivery.

DIAGRAM
0449 505 101 - 15 - © ESAB AB 2023
DIAGRAM
Valid for serial no 126-xxx-xxxx

DIAGRAM
0449 505 101 - 16 - © ESAB AB 2023

DIAGRAM
0449 505 101 - 17 - © ESAB AB 2023
Valid from serial no. 126-342-xxxx

DIAGRAM
0449 505 101 - 18 - © ESAB AB 2023

CONNECTION INSTRUCTION
0449 505 101 - 19 - © ESAB AB 2023
CONNECTION INSTRUCTION
LAF 1251

CONNECTION INSTRUCTION
0449 505 101 - 20 - © ESAB AB 2023
LAF 1251M