HTP Invertig 251: The Perfect Upgrade for Our Mechanical Contracting Business
At Industrial Welding Services, we rely on equipment that delivers when it matters most. After years of success with the HTP Invertig 221, we decided it was time to upgrade our shop machine. The Invertig 221 has been a workhorse for our mobile on-site welding jobs, consistently providing the performance we need.
As a commercial and industrial HVAC contractor, we specialize in pipe welding and process pipe welding. For in-shop heli-arc welding, we’ve used the Everlast 255ext for years. While the Everlast machine works well for TIG welding, it lacked capabilities for stick welding, particularly running 6010 electrodes. We grew tired of moving our mobile inverter machine from the truck to the shop for stick welding jobs.
The transition to the HTP Invertig 251 has been seamless. It offers the same exceptional welding characteristics we loved with the Invertig 221, but with an upgraded user interface that makes adjusting settings easier than ever. HTP also went the extra mile by offering the machine with a Miller 14-pin connector to support Miller foot pedals and hand controls.
The HTP Invertig 251 is versatile, capable of welding in both AC and DC polarity. It’s available in single 240v and dual voltage 120v/240v options, making it perfect for any shop or jobsite. With the Invertig 251, we’ve enhanced our welding capabilities and streamlined our workflow, ensuring we’re always ready for any welding process.
Comparing the Miller Maxstar 210 & the HTP Invertig 251
When we initially looked into the HTP welding machines, we compared the HTP Invertig 251 to the Miller Maxstar 210 specifically. The Miller Maxstar 210 is a proven machine and we still continue to use these machines in the field.
When comparing the two machines, you first notice the Miller has a much higher price tag and DC only. One very nice quality of the Miller Maxstar is the capability to run in 1 or 3 phase and multiple voltages from 120v, 240v, and 480v. The Miller has a very good duty cycle as well, but the HTP Invertig is not far behind.
The HTP Invertig 251 is hard to beat for the price, its available features, and great SMAW & GTAW capabilities. If you’re looking for a very capable machine in a very fair price range, look no further.
Included Accessories with the HTP 251
The HTP Invertig 251 accessory package included with the machine includes everything necessary to start tig welding. The only thing you will need to provide is an argon cylinder for shielding gas. This machine is also a very capable SMAW or stick welding machine, however you will need to provide your own stinger (electrode holder) to be able to perform this process. Also included, but not pictured is the user manual and usb update drive.
The machine we purchased utilizes the Miller 14 pin connector, to accomodate any Miller foot pedal or hand control. We have numerous Miller accessories from over the years, so having the ability to swap between those accessories was a very nice added touch by the HTP crew.
Victor Regulator
Heavy Hitter 350 Tig Rig
CK Slider Control
Ground Clamp
HTP Invertig 251 AC / DC
The HTP Invertig 251 is an Italian made welding machine that offers exceptional build quality, arc dynamics, and innovative features. It delivers 1 amp starting and 250 amp maximum output, with a user-friendly menu displayed on a 5.1” HD LCD color screen.
For career or hobby welders, the Invertig 251 can handle whatever you throw at it. It supports multiple arc starting methods, including foot pedals, slider and rotary hand controls. HTP offers a 14 pin input option to pair all your Miller Welding accessories, including Millers wireless foot pedal, cold wire feed, and more.
In DC mode, you can weld with standard TIG, pulse DC TIG, or use the Soft Pulse option for quieter welding. The DC double pulse feature is perfect for welding Titanium and Stainless steel, offering reduced heat input, HAZ, and distortion, while improving travel speed. Fast-Tack technology helps hold parts in place for precise welding.
In AC mode, you can customize waveforms for both positive and negative sides, adjust balance and frequency up to 400Hz, and choose asymmetric AC. The new zero-crossing current stabilizes the puddle for smoother welding. For thick aluminum, the Mix AC/DC feature combines DC into the AC arc for enhanced penetration, making it ideal for heavy-duty work.
Beyond TIG, the HTP Invertig 251 excels as a stick welding machine, ideal for professional pipe welders or hobbyists. It effortlessly handles 6010 5P+ electrodes and ensures smooth performance with 7018 electrodes, delivering a well-defined, smooth weld bead with superior arc characteristics.
The HTP Invertig 251 is the ultimate choice for welders seeking precision, reliability, and versatility.
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| Input Voltage | Dual Voltage 110V/220V (208 to 240V) |
| 240V Single-Phase Input Amps @ Rated Load | 30A |
| Welding Current Single-Phase (240 volt) TIG | 1 to 250A |
| Welding Current Single-Phase (120 volt) TIG | 1 to 150A |
| Welding Current Single-Phase (240 volt) STICK | 10 to 200A |
| Welding Current Single-Phase (120 volt) STICK | 10 to 110A |
| Max Rated Output TIG | 250A |
| Max Rated Output STICK | 200A |
| Open Circuit Voltage | 70V Stick – 90V TIG |
| Class | IP23S |
| Duty-Cycle (TIG) @104F @240Volt | 20% @ 250A
60% @ 160A 100% @ 130A |
| Duty-Cycle (Stick) @104F @240Volt | 25% @ 200A
60% @ 140A 100% @ 120A |
| Duty-Cycle (TIG) @104F @120Volt(20amp) | 40% @ 150A
60% @ 120A 100% @ 110A |
| Duty-Cycle (Stick) @104F @120Volt(20amp) | 40% @ 110A
60% @ 90A 100% @ 75A |
| Welding Modes | Stick TIG 2T (Pedal/Slider)TIG 2T TIG 4T TIG Spot CAC – A (Gouging) |
| Tig Process | AC, DC, AC Mix |
| TIG AC Process | AC, AC Mix, Pulse |
| TIG DC Process | Standard, Pulse, Soft Pulse, Double Pulse, Dynamic Power |
| AC Mix | Yes |
| AC Mix (DC percentage) | 10 to 90% |
| Asymmetric Arc | Yes |
| EN Amperage (%) | 10 to 100% |
| EP Amperage (%) | 10 to 100% |
| AC Frequency (Hz) 2-100A | 20 to 400Hz |
| AC Frequency (Hz) 101-250A | 20 to 200Hz |
| AC Balance (%) | 10 to 90% |
| AC Wave Forms | Square, Triangle, Sine |
| AC Wave Forms mix and match | Yes, All |
| AC Zero Crossing Current | 20 – 80A or AUTO |
| Spot Process | Standard, Fast-Tack |
| Spot Time ON (Seconds) | 0.01 to 10.0s |
| Spot Time OFF (Seconds) | 0.01 to 10.0s |
| Stick Process | Manual, Easy-SET, DC pulse, DC Soft Pulse, AC Standard |
| Pulse Stick | Yes |
| Stick Electrode Selection | Yes |
| Stick Hot Start (%) | 0 to 50% |
| Stick Hot Start Time (seconds) | 0 to 2.5s |
| Stick Arc Force (%) | 0 to 500% |
| Stick DC Polarity | Reverse (DCEP) – Straight (DCEN) |
| General Tig Settings | |
| Pre-Flow (seconds) | 0.1 to 25s |
| Post-Flow (seconds) | 0.1 to 50s |
| Initial Amps (%) | 10 to 90% |
| Initial Amps Time (seconds) | 0 to 25s |
| Final Amps (%) | 10 to 90% |
| Final Amps Time (seconds) | 0 to 25s |
| Slope Up (seconds) | 0.1 to 10.0s |
| Slope Down (seconds) | 0.1 to 10.0s |
| Tig Minimum Amp Regulation | 1 to 100A |
| Tig Hot Start | 5 to 100A or AUTO |
| Tig Tungsten Selection | Yes, .040”, 1/16″, 3/32″, 1/8″ |
| Tig Arc Starting | HF, Lift, Lift Pipe, Pipe Lift Smart |
| Pulse Parameters | |
| Stick Pulse Frequency (PPS) | 0.4 to 5.0 |
| Stick Pulse peak time (%) | 10 to 90% |
| Stick Pulse Background Amps (%) | 10 to 90% |
| Pulses/Second (PPS) TIG AC | 0.4 to 20.0 |
| Pulses/Second (PPS) TIG DC | 0.4 to 1000 |
| Peak Time (%) | 10 to 90% |
| Background Amps (%) | 10 to 90% |
| Automatic Polarity Reversal | Yes |
| Programmable Memories | 8 |
| Cooling (On Demand) | Fan Variable Speed (Forced Air) |
| Dimensions (Length x Width x Height) | 19-3/4″ x 10″ x 15-1/2″ |
| Weight (Lbs.) | 54 Lbs. |
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