Safe welding with 230V – without the fuse blowing

When using 230V welding machines in home and semi-professional settings, trips of circuit breakers (MCB) can occur.

When striking the arc during MIG/MAG or MMA welding, very high inrush currents occur briefly, which can exceed the short-term trip threshold of the circuit breaker – especially those with B-characteristic.

But the fuse can also trip during the welding process – especially with longer weld seams, high power consumption, or voltage fluctuations.

In both cases, the MCB reliably protects the installation.

The causes of these two fault cases as well as tips for troubleshooting are described below. 

Fault case 1: Fuse blows when striking the arc

At the start of the welding process, i.e. when striking the arc, a very short but high current pulse occurs. This strong current surge can exceed the limits of the installed circuit breaker, causing it to trip – the fuse "blows".

What helps against this?

• Do not simply install a stronger fuse! This can be dangerous.
• Switch off other consumers on the same circuit.
• Have your own fused socket installed – ideal for frequent welders.
• Have an electrician install a C16 circuit breaker with C-characteristic (Type C) after checking the electrical installation.

What is the difference between MCBs with B and C characteristics?

Frequently asked questions – simply explained

• Why does my fuse keep blowing?
  Because your device draws a lot of current for a short time at startup. This can be too much for circuit breakers typically installed in private households and cause them to trip. 
• Is this dangerous?
  No – the fuse protects exactly as it should.
• Can I do something about it?
  Yes! Have a C16A circuit breaker installed.
• Is this only the case with this device?
  This behaviour is not specific to RED by Lorch welding machines. Other 230V welding machines of this power class can also generate high current spikes briefly at switch-on, which can trigger an MCB.
  Such current spikes can be reduced using special technologies such as PFC or MicroBoost. Due to the higher technical effort, these functions are usually only found in welding machines of the industrial premium segment.

Conclusion

If the fuse blows when starting welding, it is usually not a defect – but simply a sign that the installed protection cannot handle the system-related start-up current. Those who weld frequently or are affected by this problem should consider adjusting the circuit breaker. Safety and enjoyment in welding are not mutually exclusive!

Note: If the fuse trips already when plugging in or switching on the device, i.e. before welding starts, please refer to the instructions in the article: "Fuse / circuit breaker trips when switching on"

Fault case 2: Fuse blows during welding

If the fuse does not trip when striking the arc but after some time, it is usually not a current spike but an overload or voltage fluctuation.
Causes can be too high continuous load, poor network quality, or long extension cables.

What helps against this?

• Switch off other consumers: Make sure no additional devices are connected to the same circuit. Parallel operation (e.g. drill, circular saw) together with the welding current can cause an overload.
• Use well-dimensioned supply lines (3×2.5 mm²): Extension cables should correspond to the fuse rating, be fully unrolled and as short as possible.
• Ensure network stability: Connect the welding machine preferably to a stable circuit (new installation, strong supply line).
• Keep the device cool: Ensure that the ventilation slots of the welding machine are not blocked and the built-in fan works. Dust and dirt on the housing should be removed to avoid overheating. Never weld if the fan is defective.
• Observe duty cycle: Plan breaks according to the duty cycle (ED). After the maximum welding time, let the device cool down to avoid thermal shutdowns (e.g. 60% ED = 6 min welding / 4 min break).
• Professional inspection: If the fuse still trips despite all measures, have the electrical installation checked by a professional. Connection errors can lead to unusually high current flow. An electrician can determine the cause in detail with measurements (current, voltage, grounding).

Frequently asked questions – simply explained

• Why does the fuse blow in the middle of welding?
  Because your device draws high currents for a longer time during operation – sometimes more than the circuit can handle continuously. This is not a defect but usually a result of low mains voltage, long supply line, or overload.
• Is my welding machine broken?
  In most cases, no. It is simply operating at the limit of what a normal 230V household line can provide.
• What can I do immediately?
  Switch off everything else on the same circuit (e.g. lights, compressor, extraction) and use a shorter extension cable with at least 2.5 mm² cross-section. This keeps the voltage more stable and prevents unnecessary current increase.
• Should I be worried?
  No. The fuse reacts as it should – it protects the wiring installation.
• Is this only the case with this device?
  This behaviour is not only observed with RED devices. Other 230V welding machines of this power class can also briefly generate high current spikes at switch-on, which can trigger an MCB. 
  Such current spikes can be reduced using special technologies such as PFC or MicroBoost. Due to the higher technical effort, these functions are usually only found in welding machines of the industrial premium segment.

Conclusion

An occasional tripping of the fuse during welding is not an indication of a defect in the device. The MCB protects the wiring – exactly as it should.

If you notice unusual behaviour or want to be on the safe side, please contact the RED by Lorch service team via the contact form.