The Lincoln Electric 6-PACK RACK FLEXTEC 500 MULTI-PROCESS WELDER (K4099-1) is a factory-wired, six-welder industrial rack system housing six FLEXTEC 500 multi-process inverter power sources on a single portable rack with one shared primary power connection. Rated at 500 A per welder, the FLEXTEC 500 delivers higher output than the FLEXTEC 450 rack variants — making the K4099-1 the right specification for heavy structural steel, thick-plate FCAW, and demanding construction environments where six operators need simultaneous high-amperage weld output. The system ships factory-installed with all power sources pre-wired to the internal distribution panel, fully NEC-compliant and IP23-rated.
| Parameter | Value |
|---|---|
| Model / SKU | 6-PACK RACK FLEXTEC 500 / K4099-1 |
| Number of Power Sources | 6 × FLEXTEC 500 |
| Output per Welder (Rated) | 500 A / 40 V @ 60% duty cycle |
| Output per Welder (100% DC) | 450 A / 38 V |
| Input Power | 380–600 V, 3-phase, 50/60 Hz |
| Main Disconnect | Common 3-phase disconnect switch |
| IP Rating | IP23 |
| Processes per Welder | MIG (GMAW), FCAW, Stick (SMAW), DC TIG |
| Lifting | Overhead lifting eyes |
| Fork Slots | Two forklift slots |
| Fusing | Individual per power source |
| Standards | NEC-compliant; CE, UL, CSA per individual FLEXTEC units |
The 6-Pack Rack FLEXTEC 500 is the go-to specification for large-scale construction and fabrication projects requiring the highest per-welder output in a portable multi-operator format:
- Heavy structural steel and bridge fabrication — Six 500 A welders operating simultaneously on heavy plate and rolled sections, with one primary power drop for the full rack.
- Offshore platform and ship construction — High-amperage FCAW on thick hull sections; IP23 rating for marine environmental exposure.
- Industrial construction (refineries, power plants) — Turnaround and new construction requiring concentrated welding manpower, with single-point safety disconnect for lockout/tagout compliance.
- Modular and skid fabrication — High-output FCAW and multi-process capability on steel-intensive module packages.
- Pipeline construction support — Forklift slots and lifting eyes for rapid rack repositioning as the construction front moves.
The FLEXTEC 500 platform in this rack is optimized for simplicity and reliability at higher output levels:
- 500 A Output per Welder — Each FLEXTEC 500 delivers 50 A more rated output than the FLEXTEC 450, enabling higher deposition rate FCAW on thick structural members and eliminating the need to derate from the 60% duty cycle rating during normal production.
- Simple Operator Panel — The FLEXTEC design philosophy eliminates unnecessary operator controls. Process selection and input power connection are streamlined, reducing setup errors and training time for new operators.
- 380–600 V Multi-Voltage Input — Single primary connection covers US 460 V, Canadian 575 V, and international 380 V three-phase services, simplifying specification for international projects.
- Broad Feeder Compatibility — FLEXTEC 500 is compatible with analog across-the-arc feeders (LN-25X, LN-15), digital ArcLink feeders, and downstream wire feeder systems for FCAW-G and GMAW production.
- IP23 Environmental Rating — All six FLEXTEC 500 units are rated for outdoor and light-precipitation environments per IEC IP23, matching the demands of heavy construction jobsites.
- Individual Overcurrent Fusing — Each power source has its own fuse for independent overcurrent protection — a fault on one welder does not interrupt the remaining five operators.
- Factory-Installed and Pre-Wired — Rack arrives with all six units installed in the rack and connected to the internal distribution panel, eliminating field wiring labor on the primary conductor and distribution panel.
The six FLEXTEC 500 outputs in the K4099-1 rack support the same feeder compatibility as standalone FLEXTEC units:
- Lincoln LN-25X Extra Torque (K4267-5) — Preferred for high-deposition 3/32 in. FCAW wire; CrossLinc voltage control over the weld cable without additional cables.
- Lincoln LN-25X K4267-4 — Standard torque with flowmeter for GMAW and standard-diameter FCAW.
- Lincoln 4-Pack Rack FLEXTEC 450 (K2956-2) — Lower-output 4-welder configuration for applications not requiring full 500 A output.
- LN-15 across-the-arc feeders — For conventional FCAW and SMAW setups without CrossLinc.
Browse the full range of Lincoln multi-operator systems and welding equipment at WeldingMart.
What is the per-welder output of the 6-Pack Rack FLEXTEC 500?
Each of the six FLEXTEC 500 power sources in the K4099-1 delivers 500 A at 60% duty cycle (40 V) and 450 A at 100% duty cycle (38 V). For continuous production welding, the 450 A / 100% rating is the appropriate ceiling for long-duration weld passes.
How does the 6-Pack Rack FLEXTEC 500 differ from the 4-Pack Rack FLEXTEC 450?
The 6-Pack Rack K4099-1 houses six FLEXTEC 500 power sources (500 A rated) versus four FLEXTEC 450 units (450 A rated) in the 4-Pack K2956-2. The 6-Pack is specified for larger crews and higher-output requirements; the 4-Pack is the choice when four welding stations at 450 A is sufficient.
What input power is required for the 6-Pack Rack FLEXTEC 500?
The K4099-1 accepts 380–600 V, 3-phase, 50/60 Hz. A licensed electrician must verify panel ampacity to support six simultaneous 500 A welding loads before installation. Consult Lincoln's installation documentation for minimum service conductor sizing.
Can I use the LN-25X with CrossLinc on the 6-Pack Rack FLEXTEC 500?
Yes. The FLEXTEC 500 supports CrossLinc operation, so each LN-25X feeder (K4267-4 or K4267-5) can control voltage at the feeder location without a separate control cable. Pair one LN-25X per FLEXTEC 500 output for maximum flexibility on long cable runs.
Is the K4099-1 rack suitable for outdoor and construction environments?
Yes. The FLEXTEC 500 power sources are IP23-rated for outdoor and light-precipitation environments. The rack enclosure protects the primary wiring and distribution panel from direct weather exposure. For severe wet environments, additional weather enclosure protection is recommended.
Does the 6-Pack Rack have casters?
The K4099-1 ships with forklift slots and overhead lifting eyes for crane or forklift positioning. Casters are not included in the base configuration; contact WeldingMart for caster kit options compatible with this rack model.