Rtech MTS 255HF User manual

www.r-techwelding.co.uk
email: [e-mail]
Tel: [phone] Fax [phone]
MTS 255HF
MIG-TIG-MMA WELDING MACHINE
OPERATION INSTRUCTIONS
Version 2020-10

2

3
Thank you for selecting the R-Tech MTS255-HF Inverter MIG (Synergic) - MMA – HF DC TIG Welder.
The MTS255-HF has many benefits over traditional transformer welders including infinite power control,
adjustable arc force and features a heavy duty wire feed mechanism to provide very smooth wire feed and
weld characteristics
Ideal for automotive work with its minimum current of 25-30 Amps and industrial welding with its
maximum output of 250 Amps (MIG/TIG) and 200 amps (MMA)
We want you to take pride in operating our MTS255-HF as much pride as we have taken in making this
product for you. Please read all information in this manual before operation
PLEASE EXAMINE CARTON AND EQUIPMENT FOR DAMAGE IMMEDIATELY
Please record your equipment identification below for future reference. This information can be found on the data plate at
rear of machine.
Product: MTS255-HF
Serial No..
Date of Purchase
Where Purchased
Whenever you request replacement parts or information on this equipment please always supply the
information you have recorded above
This product is covered by 3 years parts and labour warranty, we will cover cost of collection, repair and returning item to you
within mainland UK (other areas are RTB warranty). External items, torch, earth lead etc. are covered by 3 months warranty.
Any faults/damage found caused by customer will be charged pro-rata.
Please read this operator manual completely before attempting to use this equipment. Pay particular attention
to the safety instructions we have provided you for your protection
The level of seriousness to be applied to each section is explained below
WARNING
This statement appears where the information must be followed exactly to avoid serious personal injury.
CAUTION
This statement appears where the information must be following to avoid a minor personal injury or damage to this equipment.

4
Product Description
Premium features include: -
• Inverter power source – more efficient to operate, provides smoother weld characteristics.
• Heavy duty wire feed unit for long working life and consistent wire feeding.
• MIG (Synergic) - MMA - DC Tig welding modes
• Infinite welding voltage to allow fine tuning of weld characteristics
• Adjustable arc force – controls splatter – ideal for thin materials
• Synergic MIG Operation with settings for steel, stainless steel and aluminum
• MIG Operation with from 25 amps to 250 amps - ideal for very thin and thick materials
• Digital amp & volts meters
• 9 memory job stores - Easily switch between stored settings for job in hand
• Euro type torch fittings for easy torch fitment/replacement
• 35% Duty cycle at maximum amps @ 40ºC
Recommended Processes
The R-Tech is recommended for the MIG welding processes within its output capacity of 250 Amps DC
Equipment Limitations
The R-Tech POWER MTS255-HF is protected from overloads beyond the output ratings and duty cycle as per machine
specifications with thermostat protection of the output coils and rectifiers.
Welding Capability Duty Cycle
The R-Tech MTS255-HF is rated at 250 Amps (MIG) at 35% duty cycle on a ten-minute basis. If the duty cycle is
exceeded a thermal protector will shut machine off until the machine cools.
The R-Tech MTS255-HF is rated at 200Amps (MMA) at 35% duty cycle on a ten-minute basis. If the duty cycle is
exceeded a thermal protector will shut machine off until the machine cools.
The R-Tech MTS255-HF is rated at 250 Amps (TIG) at 35% duty cycle on a ten-minute basis. If the duty cycle is
exceeded a thermal protector will shut machine off until the machine cools.

5
Technical Specifications
Installation
Model No.
R-Tech MTS255-HF
Input
240V 1 ~ AC 50/60Hz
Operation
Rated Input Current
32AMPS
Rated Output Current
250 AMPS
Duty Cycle 35% @ 40OC
250A (MIG/TIG) ,200A(MMA)
Duty Cycle 100% @ 40OC
160A (MIG/TIG),130A(MMA)
Output current Range
MIG: 30-250 AMPS
MMA: 10-200AMPS
TIG: 10-250 AMPS
No Load Voltage
60~80V
MIG Voltage Adjustment
Range
14V - 29V± 3V
Suitable Wire Diameter
0.6mm 0.8mm 1.0mm
Insulation
Class F
Read entire section before starting installation
WARNING!
Electric Shock can kill, only qualified personnel should perform this installation. Turn off input power at the fuse box before
working on this equipment. Do not touch electrically live parts. Always connect the machine to an earthed main supply as
per national recommended standards.
Select suitable location
Place the welder where clean cooling air can freely circulate in and out of the front & rear louvre vents. Dirt, dust or any foreign
material that can be drawn through vents into welder must be kept to a minimum. Failure to observe these precautions can
result in excessive operating temperatures which can lead to plant failure.
Grinding
Do not direct grinding particles towards the welder. An abundance of conductive material can cause plant failure.
Stacking
This machine cannot be stacked.

6
Transport & Unloading
Never underestimate the weight of equipment, never move or leave suspended in the air above people. Always use
recommended lifting equipment.
WARNING!
Falling Equipment can cause injury. Never lift welder with gas bottle attached. Never lift above personnel.
Tilting
Machine must be placed on a secure level surface or on a recommended undercarriage/trolley. This machine may
topple over if this procedure is not followed.
Environmental Rating
The welding power source carries the IP21S rating. It may be used in normal industrial and commercial
environments. Avoid using in areas where water / rain is around.
Read and follow the Electric Shock Warnings in the safety section if welding must be performed under electrically
hazardous conditions such as welding in wet areas or water on the work piece.
Machine grounding and High Frequency Interference Protection
This welder must be grounded to earth. See national electrical codes for proper grounding methods.
The high frequency generator is like a radio transmitter and may cause interference to radio, TV and other electronic
equipment. These problems may be the result of radiated interference. Proper grounding methods can reduce or eliminate this.
Radiated interference can develop in the following ways
• Direct interference from welder power source
• Direct interference from the welding leads
• Direct interference radiated from feedback into power lines
• Interference from re-radiation by un-grounded metallic objects.
Keeping these contributing factors in mind, installing equipment as per following instructions should minimize problems.
• Keep the welder input power lines as short as possible and enclose as much of them as possible in metal conduit or
equivalent shielding. There should be a good electrical contact between this conduit and ground (Earth).
• Keep the work and electrode leads as short as possible. Tape the leads together where practical.
• Be sure the torch and earth lead rubber coverings are free from cuts and cracks that allow welding power
leakage
• Keep earth lead connection to work in good condition Clean area on workbench where earth clamp is
situated on a regular basis.

7
Input Connections
Make sure the voltage, phase and frequency of input power is as specified on machine rating plate located at rear of machine.
Have a qualified electrician provide suitable input power as per national electrical codes. Make sure machine is earthed /
grounded.
Make sure fuse or circuit breaker is correct rating for machine. Using fuses or circuit breakers smaller than
recommended will result in nuisance shut off from welder inrush currents even if welding at low amperages.
On multiple voltage input welders, be sure the machine is connected as per the instructions for the voltage being supplied to
welder Failure to follow these instructions can cause immediate failure within the welder and void machines warranty.
WARNING!
ELECTRIC SHOCK CAN KILL
Turn the input power OFF at the mains switch & fuse box before working on this equipment. Have a
qualified electrician install & service this equipment.
Allow machine to sit for 5 minutes minimum to allow the power capacitors to discharge before working inside this
equipment. Do not touch electrically live parts
The POWER MTS255-HF Inverter Tig Welder requires a 240V 50/60Hz 32amp fused supply. It comes with a 3
metre mains cable attached.
Connect wires according to national coding. (Below states UK coding) Brown wire - Live, Blue
wire - Neutral, Green/Yellow Wire - Earth (Ground)
Connecting to a mains electrical supply
THIS MACHINE IS OF AN INDUSTRIAL SPECIFICATION AND MUST BE FITTED
TO A 32AMP 240V MAINS INPUT
Connecting to an Engine Driven Generator
If connecting this machine to an engine driven generator, please ensure the
following Minimum Generator KVA Output - 10 KVA continuous Generator to
be fitted with AVR (automatic voltage regulation)
DO NOT USE ON A GENERATOR WITHOUT AVR, connecting to a generator without
the above minimum requirements may invalidate your warranty.

8
Controls and Settings
Front Panel
Fig 1
1) Voltage /MMA Arc-force/TIG down slope Display
The meter on the front panel indicates the actual welding voltage or preset MIG voltage.
Display 1, Volts, Seconds and Percent
2) Current /Wire speed indicating
The current indicating meter on the front panel indicates the actual welding current during the welding，indicates
the wire speed during no welding.
Display 2, Amps & Meters Per Minute
3) Power On indicator.
This will light up when power to the machine is connected and on/off switch in ON position.
4) MIG & TIG post flow gas time in seconds
5) Wire speed - When lit LED display will show wire feed speed in inch/min
6) Current - When lit LED display will show amperage in MIG / TIG / MMA mode

9
7) MIG / TIG / MMA Process Selector
The 1st function represents MIG welding mode in either STD mode (Manual) or SYN mode (SYNERGIC)
The 2nd function represents TIG welding mode.
The 3rd function is MMA (Stick welding),
8) Voltage - When lit LED display 1 will show weldingvoltage
9) Forward selector button
Use this to cycle forwards through the welding parameters
10) Back selector button
Use this to cycle backwards through the welding parameters
11) Duty Cycle / Over current Warning
When the duty cycle has been exceeded or an over current condition will occur, the LED will light. Allow the unit to
cool while running until the light goes off or for 10 minutes before resetting the welder. If the condition persists,
check for loose wires or voltage supply problems or call R-Tech support.
12) Memory channel LED
This displays current memory job number 1 - 9
13) CH (channel) / SAVE & Process Selector
Pressing button will change memory store number and show values stored. To set up a new memory store first
select number to be programmed, then enter setup parameters as required and then press save for 3 seconds to
program current setting to shown memory number, the save LED will light once saved.
14) MMA / STICK parameters
Press to select function required, this will be shown in display (1) and can be adjusted with knob (18)
ARC Force % - This controls the arc response to when electrode is held close/away from workpiece. Arc force
automatically adjusts by changing the volts / amps to maintain a stable arc.
HOT Start % - For controlling the amount of extra amps when the arc is first started and prevents the
electrode sticking to work. Adjustable from 0 - 100% of hot start amps available.
Hot Start Time - Adjusts the time in 0-2 seconds that the hot start will happen at beginning of weld. This helps
to reduce electrode sticking to work.
15) 2T/4T and Pedal/Spool Gun Switch Selector
The torch trigger function is designed to operate for both MIG and TIG functions.
2T (MIG/TIG) - The trigger on either the MIG or TIG torch should be simply held down to start weld and released
when finished welding.
4T (MIG/TIG) - function operates as a torch latch in MIG & TIG mode that locks the torch on without needing to hold
the trigger down when welding.
To operate 4T in MIG mode, simply press the torch trigger and hold it down until the arc starts. To lock it
on, release the trigger and you can then weld without holding the trigger down. To stop, the trigger must be
pressed again and then released.

10
The 4T function in TIG mode acts similarly, but in conjunction with the up/down slope timer. As the torch trigger is
pressed for the second time, the trigger should be held in until the downslope timer completes its cycle. The trigger
may then be released to end the arc. Releasing before the down slope is finished will terminate the arc immediately.
PEDAL is for using the optional remote foot pedal to control TIG amps when welding.
SPOOL is for using the option Spool-on MIG gun. Please note when using spool gun, the wire speed is not controlled
by knob on spool gun, it is controlled from the front panel
16) Wire type selector
Select your wire type according to the basic categories of Steel, S.S (Stainless Steel) or AL(Aluminum). This
input must be made to properly use the Synergic function to automatically adjust the Volts needed to weld at the
selected wire speed.
17) Wire Diameter Selector
Select your wire diameter according of the type wire you are using. Selecting the correct wire diameter is critical to
optimum Synergic function of the welder, automatically compensating the voltage while the wire speed is adjusted.
For alternate full manual control of the welder to function in “normal” MIG mode, select STD. This will allow for full,
independent control of MIG wire speed and voltage.
18) Welding parameter adjustment knob.
When cycling through the various welding settings available, when you have highlighted the parameter you require
using the forward/back buttons (9,10) use this knob to adjust setting which will be shown in display 1 or 2.
19) TIG Start - HF or Lift start selector
Select HF start for automatic TIG arc starting, press trigger with tungsten away from workpiece and arc will start.
Select Lift Start if working on vehicles etc. with sensitive electronics, press trigger and touch tungsten on workpiece
then lift and arc will start.

11
Rear machine connections
Fig2
1 Mains input cable (240V AC input)
Fit the required plug as per your electrical installation
2 On/Off Switch
3 Fuse Holder
5A fuse for wire speed motor
4 Gas input connector
Connect input gas hose ensuring connection is tight

12
Connections for TIG (GTAW) Welding
Fig 3
1) Gas outlet
Connect the TIG torch gas hose quick release connector
2) MIG Torch Euro Connector (NOT used in TIG mode)
3) Positive power connector +
Connect the earth lead to by inserting and twisting until tight and the earth clamp to work/ bench
4) Torch switch / Foot pedal socket
Connect TIG torch control plug or Remote Foot Pedal plug
5) Negative power connector -
Connect TIG Torch Dinse to power connector by inserting and twisting until tight
Connect the gas input hose to gas regulator and use 'Pure Argon' Gas, available from local suppliers. Set gas
flow/pressure to 8 LPM, make sure the gas bottle is secured to avoid injury.

13
Fig
Connections for MMA STICK (SMAW) Welding
1 Gas outlet (NOT used in MMA mode)
2 MIG Torch Euro Connector (NOT used in MMA mode)
3 Positive power outlet – Connect electrode holder lead
4. Remote connection (NOT used in MMA mode)
5. Negative power outlet – Connect earth lead

14
Connections for MIG Welding
1 Gas outlet (NOT used in MIG mode)
2 MIG Torch Euro Connector - Connect MIG Torch.
When using Spool Gun for aluminium welding connect torch here and 7 pin plug to socket (4)
3 Positive - Not normally used unless using gasless wire (reverse polarity)
4. Remote connection (NOT used in MIG mode)
If using Spool-On Gun, connect the 7-pin plug here.
5. Negative power outlet – Connect earth lead.

15
How to fit wire reel for MIG mode
TO INSTALL WIRE:
1. Wire reel holder - remove retainer screw cap and fit wire reel and refit securing screw cap. The reel holder features an
internal adjustable braking system so that reel of wire stops quickly when the torch trigger released.
2. Loosen top tensioner arm, rotating counterclockwise
3. Flip tensioner down, releasing top drive rolls.
4. Raise top drive rolls.
5. Inspect the drive roll to make sure that the groove size matches the wire diameter. Reversal of the lower roller may be
necessary. To reverse the roller, remove the thumb screw securing the drive roll. Pull the drive roll off and flip the drive roll
over. Reassemble and tighten roller. If larger roller is needed, contact R-Tech. Be careful to replace the woodruff key between
outer roller and shaft.
6. Thread straightened welding wire over grooves in lower drive roll fully through until it begins to start threading into the gun
section. Lower upper drive rolls onto lower drive roll, keeping wire in the groove.
7. Raise tensioner back into place. Tighten slightly so wire will feed. Notice markings on tensioner for future reference.
8. Hold torch straight out as possible. Press gun trigger to feed wire until the wire exits the end of the torch.
9. Do not over tighten the wire feed pressure rollers as this can cause premature motor and roller failure.
TIP: Correct way to adjust tensioner is to slacken off pressure so that the wire does not feed, slowly adjust pressure until wire
feeds smoothly, you should be able to stop wire feeding by holding wire and it should slip on rollers. If you have too little
pressure the wire will slip when welding causing unwanted burn back into tips, if you have too much pressure wire can snag
in rollers when wire hits work and cause wire tangle by rollers.

16
Connections for using gas / gasless wire
Ensure machine is disconnected from mains before changing torch polarity
When welding with gasless wire you need to reverse the polarity of welding power.
Gas welding is negative earth and positive wire (torch)
Gasless welding is positive earth and negative wire (torch)
1. Gas type wire
Connect as per diagram above, A is power outlet, B is + to torch Fit earth lead to -
negative connector on front of machine
2. Gasless type wire (reverse polarity required for gasless wire)
Connect brass bar from A to C so torch is negative
Fit earth lead to + positive connector on front of machine
Note: Ensure machine is disconnected from mains before changing torch polarity.

17
Operation
SAFETY PRECAUTIONS
WARNING!
ELECTRIC SHOCK CAN KILL
Do not touch electrically live parts or electrode with skin or wet clothing.
Insulate yourself from work and ground Always
wear dry insulating gloves
WARNING!
FUMES AND GASES can be dangerous
Keep your head out of fumes & gases produced from welding.
Use ventilation or exhaust to remove fumes & gases from breathing zone and general area.
WARNING!
WELDING SPARKS can cause fire or explosion Keep
flammable material away from work area.
Do not weld on containers that have held combustibles
WARNING!
ARC RAYS can burn
Wear eye, ear and body protection Make sure work area is protected by proper shielding to avoid injury to passers-
by.

18
Welding in MIG STD (Manual) Mode
1 Connect the MIG Torch to machine, connect earth lead to machine & work piece.
2 Fit wire reel to machine using guide on page 15
3 Connect welding gas and set flow to approx. 12-14 LPM
4 Set the machine mode to MIG STD (No. 7 front panel)
5 Select 2T or 4T torch operation. (No. 15 front panel)
6 Use the forward and back buttons (No. 9 & 10 front panel) to select any parameters you wish to change then use the
control knob to adjust as required (No. 18 front panel)
Pre-flow gas - Set at 0.1s for most jobs, if longer gas purge is required set accordingly.
MIG wire speed – adjust with control knob (No. 18 front panel) and speed will be shown in display 2
MIG volts - adjust with control knob (No. 18 front panel) and speed will be shown in display 1
Post flow gas – For most MIG welding along post flow gas is not required.
MIG burn back – This is time power/gas stays on after trigger released – this will burn wire back towards tip.
MIG inductance – low setting softer arc with low splatter , high setting harsher arc with deeper penetration.
We suggest setting in middle for most jobs.
Welding operation
Once you have set the machine up as per above instructions press the torch trigger to start welding, gas will flow from the torch
and main welding power will start and wire feed will start and once wire has touched work piece welding will start, to stop
welding release torch trigger.
Adjust the wire feed speed to give the desired weld characteristics
More wire / Less voltage = Dip transfer
Less wire / More voltage = Spray transfer

19
Welding in MIG SYN (Synergic) Mode
1 Connect the MIG Torch to machine, connect earth lead to machine & work piece.
2 Fit wire reel to machine using guide on page 15
3 Connect welding gas and set flow to approx. 12-14 LPM
4 Set the machine mode to MIG SYN (No. 7 front panel)
5 Select 2T or 4T torch operation. (No. 15 front panel)
6 Use the forward and back buttons (No. 9 & 10 front panel) to select any parameters you wish to change then use the
control knob to adjust as required (No. 18 front panel)
Wire type – select either Steel, Stainless Steel or Aluminium wire (No. 16 front panel)
For Steel you will require a mixed Co2/Argon gas
For Aluminium welding you will require 100% pure argon gas.
Pre-flow gas - Set at 0.1s for most jobs, if longer gas purge is required set accordingly.
MIG volts - adjust with control knob (No. 18 front panel) and speed will be shown in display 1
In synergic mode, when you adjust voltage the wire feed speed will automatically adjust.
Post flow gas – For most MIG welding along post flow gas is not required.
MIG burn back – This is time power/gas stays on after trigger released – this will burn wire back towards tip.
MIG inductance – low setting softer arc with low splatter , high setting harsher arc with deeper penetration.
We suggest setting in middle for most jobs.
Welding operation
Once you have set the machine up as per above instructions press the torch trigger to start welding, gas will flow from the torch
and main welding power and wire feed will start, once wire has touched work piece welding will start, to stop welding release
torch trigger.
In synergic mode you can trim the wire speed to give the desired weld.
The machine automatically presets wire feed speed to voltage and wire type / diameter selected, sometimes this will need fine

20
adjustment to suit your welding style / requirements. Select MIG voltage (MIG volts LED lit) an adjust voltage to suit. See Page
24 for more information.
More wire / Less voltage = Dip transfer
Less wire / More voltage = Spray transfer