The ESAB LAF 1251 / LAF 1251M are remote-controlled, 3-phase welding power sources designed for high-efficiency mechanical submerged-arc welding (SAW). These units are fan-cooled and incorporate a thermal cutout for overload protection. When an overload occurs, a yellow lamp on the front panel illuminates, and the unit automatically resets once the temperature returns to a permitted level.
Users are responsible for observing all relevant safety precautions, which must meet the requirements for this type of equipment. All work must be carried out by trained personnel familiar with the equipment's operation. Operators must ensure no unauthorized persons are in the working area when the equipment starts and that no one is unprotected when the arc is struck. The workplace must be suitable for the purpose and free from drafts. Personal safety equipment, such as safety glasses, flame-proof clothing, and safety gloves, should always be worn. Loose-fitting items like scarves, bracelets, and rings should be avoided as they can become trapped or cause burns. General precautions include ensuring the return cable is securely connected and that work on high-voltage equipment is only performed by a qualified electrician. Appropriate fire extinguishing equipment must be clearly marked and close at hand. Lubrication and maintenance should not be carried out during operation.
Warnings and Cautions:
- DANGER! Immediate hazards can result in immediate, serious personal injury or loss of life.
- WARNING! Potential hazards can result in personal injury or loss of life.
- CAUTION! Hazards can result in minor personal injury.
- ELECTRIC SHOCK - Can kill: Install and ground the unit according to the instruction manual. Do not touch live electrical parts or electrodes with bare skin, wet gloves, or wet clothing. Insulate yourself from work and ground, and ensure a safe working position.
- ELECTRIC AND MAGNETIC FIELDS - Can be dangerous to health: Welders with pacemakers should consult their physician before welding, as EMF may interfere with pacemakers. To minimize exposure, route electrode and work cables together on the same side of your body, securing them with tape. Do not place your body between the torch and work cables, and never coil the torch or work cable around your body. Keep the welding power source and cables as far away as possible. Connect the work cable to the workpiece as close as possible to the welding area.
- FUMES AND GASES - Can be dangerous to health: Keep your head out of the fumes. Use ventilation, extraction at the arc, or both, to remove fumes and gases from your breathing zone and the general area.
- ARC RAYS - Can injure eyes and burn skin: Protect your eyes and body with 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 with earmuffs or other hearing protection.
- MOVING PARTS - Can cause injuries: Keep all doors, panels, and covers closed and securely in place. Only qualified personnel should remove covers for maintenance and troubleshooting. Reinstall panels/covers and close doors after service. Stop the engine before installing or connecting the unit. Keep hands, hair, loose clothing, and tools away from moving parts.
- FIRE HAZARD: Sparks (spatter) can cause fire. Ensure no inflammable materials are nearby. Do not use on closed containers.
- HOT SURFACE - Parts can burn: Do not touch hot parts barehanded. Allow a cooling period before working on equipment. Use proper tools and/or insulated welding gloves to handle hot parts.
- MALFUNCTION: Call for expert assistance in the event of malfunction.
- 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, due to potential difficulties in ensuring electromagnetic compatibility.
- NOTE! Dispose of electronic equipment at a recycling facility in observance of European Directive 2012/19/EC. It is the user's responsibility to obtain information on approved collection stations.
Installation:
Installation must be carried out by a professional.
- Mains supply requirements: High power equipment may affect grid power quality. Connection restrictions or requirements regarding maximum permissible mains impedance or minimum supply capacity may apply. The installer or user is responsible for ensuring the equipment can be connected, consulting the distribution network operator if necessary.
- Location: Secure the equipment, especially on uneven or sloping ground (not exceeding 10°). Place the welding power source on a level foundation and ensure nothing obstructs cooling.
- Connections:
- The welding power source is connected for 400 V. For other supply voltages, remove the left side plate and perform the switchings on the main and control transformer according to the "CONNECTION INSTRUCTION" chapter.
- Connect the mains cable with the correct cable area and fuse according to local regulations (refer to the "Mains connection" section).
- Remove the front plates (x 2).
- Connect the ground cable to the screw marked with the ground symbol.
- Tighten the cable clamp.
- 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):
- 380/400/415/500 V, 3~50 Hz; 440/550 V, 3~60 Hz. Imax 104 A.
- Cable area (mm²): 3x70 + 35 (380/400/415/500 V, 50 Hz); 3x35 + 25 (440/550 V, 60 Hz).
- Fuse, slow (A): 120 (380/400/415/500 V, 50 Hz); 100 (440/550 V, 60 Hz).
- Mains connection (LAF 1251M):
- 220/230/400/415/500 V, 3~50 Hz; 230/400/440/550 V, 3~60 Hz. Imax 171 A.
- Cable area (mm²): 3x70 + 35 (220/230/400/415/500 V, 50 Hz); 3x35 + 25 (230/400/440/550 V, 60 Hz).
- Fuse, slow (A): 160 (220/230/400/415/500 V, 50 Hz); 100 (230/400/440/550 V, 60 Hz).
- The mains cable areas and fuse sizes are based on Swedish regulations. For other regions, supply cables must be suitable for local and national regulations.
Operation:
- Never use the welding power source without side plates.
- The power source must be set to analogue mode to use the PEI control unit.
- Front panel controls:
- Main circuit-breaker: Switches mains voltage and fan on/off. Position "1" is On, "0" is Off.
- Indicator lamp (white): Illuminates when the main switch is On.
- Indicator lamp for overheating (yellow): Illuminates when the thermal cutout is deployed due to excess temperature. Goes out when the temperature decreases to a permitted level.
- Pushbutton: Resets the automatic fuse FU2 for 42 V supply voltage.
Technical Specifications:
- Permissible load at 100% duty cycle: 1250 A / 44 V (for both LAF 1251 and LAF 1251M).
- Setting range: 100-1250 A / 24-44 V (for both models).
- No-load voltage: 53 V (for both models).
- No-load power: 210 W (for both models).
- Efficiency at max current: 89% (LAF 1251), 88% (LAF 1251M).
- Power factor at max current: 0.89 (LAF 1251), 0.94 (LAF 1251M).
- Apparent power at max current: 69 KVA (for both models).
- Active power at max current: 61.7 kW (for both models).
- Operating temperature: -10 to +40 °C (for both models).
- Continual sound pressure at no-load: <70 dB(A) (for both models).
- Weight: 490 kg (for both models).
- Dimensions L × W × H: 774 × 598 × 1430 mm (for both models).
- Insulation class (transformer): H (for both models).
- Enclosure class: IP 23 (for both models). This indicates protection against penetration by solid objects or water. Equipment marked IP23 is suitable for indoor and outdoor use.
- Application class: S (for both models). This symbol indicates the power source is designed for use in areas with increased electrical hazard.
Maintenance:
- All warranty undertakings cease if the customer attempts any work to rectify faults during the warranty period.
- Cleaning the welding power source: Clean as necessary. Dry compressed air is recommended. Blocked air inlets or outlets will lead to overheating.
- Cleaning the contactor: Never use compressed air to clean the contactor without first taking it apart completely. To ensure reliable operation, magnetic parts must be kept clean. If cleaning is necessary, the contactor must be disassembled, and all pieces cleaned. Alternatively, the contactor can be replaced.
Ordering Spare Parts:
- Repair and electrical work should be performed by an authorized ESAB service technician using only ESAB original spare and wear parts.
- The LAF 1251 / LAF 1251M is designed and tested according to IEC-/EN 60974-1 and IEC-EN 60974-10. The service unit performing repairs must ensure the product still conforms to these standards.
- Spare parts and wear parts can be ordered through your nearest ESAB dealer (esab.com). When ordering, state product type, serial number, designation, and spare part number from the spare parts list for correct delivery.
- Ordering numbers:
- 0460 514 880: Welding power source LAF 1251
- 0460 514 881: Welding power source LAF 1251M
- 0459 839 058: Spare parts list LAF 1251 / LAF 1251M
- The spare parts list is available as a separate document on www.esab.com.
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