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# Welder - what sort of amp input it will need at 240v

Discuss Welder - what sort of amp input it will need at 240v in the Commercial Electrical Advice area at ElectriciansForums.net

#### 2189clarky

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I recently bought a welder (picture attached) I was wondering what sort of amp input it will need at 240v

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#### Lucien Nunes

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It states the kVA rating at its normal duty cycle as 5kVA. 5000/230= 22 amps. However the peak current may be higher depending on what type of work you are doing and what current you select. As a guide, multiplying the maximum handpiece current by the O/C volts for the 80V tap gives 130 x 80 = 10.4kVA output which could require 50A or more input, although it will not demand this current continuously. The inrush at switch-on may be hefty too, which might influence your choice of OCPD.

#### Megawatt

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I recently bought a welder (picture attached) I was wondering what sort of amp input it will need at 240v
That’s an old welder but look in the back of the welder, after you isolate all power and you will have to take the back off and look in there should be the wiring diagram and you can change the taps depending on your voltage

#### Firedancer

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I recently bought a welder (picture attached) I was wondering what sort of amp input it will need at 240v
have a look in the handbook or if you dont have it search online for it, it will state a required supply, mine at max demand runs at 33A but I run it on a 13A plug as its a portable unit and theres only one 32A socket around the site. I weld stuff usually between 3mm-10mm thickness without any problems, only ever trips if I turn it right up to get deeper penetration on something in a high stress application.

#### ian.settle1

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have a look in the handbook or if you dont have it search online for it, it will state a required supply, mine at max demand runs at 33A but I run it on a 13A plug as its a portable unit and theres only one 32A socket around the site. I weld stuff usually between 3mm-10mm thickness without any problems, only ever trips if I turn it right up to get deeper penetration on something in a high stress application.

Handbook looking at the age of it, it's probably written in Old English

#### 2189clarky

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That’s an old welder but look in the back of the welder, after you isolate all power and you will have to take the back off and look in there should be the wiring diagram and you can change the taps depending on your voltage
Already swapped it to 240 just need to know what size cable to run to my shed for it.

#### Paignton pete

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Already swapped it to 240 just need to know what size cable to run to my shed for it.

#### Lucien Nunes

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Well as I said in post #2 the average running current will be in the order of 20A but the peak maybe 50. You will need to be careful with voltage drop in the supply cable otherwise fluctuations in the welding current may affect other loads (although LEDs with electronic drivers should be pretty immune to flicker). As George Cooke mentions in the other thread, even other customers on the network can be affected by the spiky nature of an MMA welding load.

#### static zap

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5kVA. 5000/230= 22 amps.
I can vouch for more amps at times.
( >26A if got rod stuck )

#### Lucien Nunes

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I did mention that the 5kVA relates to the maximum load at which the welder will sustain its rated duty cycle, and that the peak might be over twice that. This is one of the distinctions between a 'hobby grade' welder and an industrial one; the industrial unit has a much higher open-circuit voltage and hence higher maximum instantaneous power. This unit offers two ranges, if you want max current you have to work with reduced OCV.

Hobby non-inverter welders universally rely on a variable magnetic shunt to control the welding current, which significantly affects the power factor and makes the supply current a function of both the setting and the arc current. The tapped transformer in this unit probably presents a better pf all round, but the peak current especially on inrush is something to be reckoned with.

#### oracle

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Wish I had a picture of a homemade welding “machine “ I once saw. The guy used a four element bar heater wired in series with the welding handle.

To vary the welding current he combined more or less bar elements in parallel. His open circuit voltage was 230v and his lights dimmed when he struck an arc.

#### steve50

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do you know when the oil was last changed as dirty oil will effect the welder performance could make draw more currant and lay a bad bead

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#### EricMark

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In the main welding voltage is 25 volt plus one volt for every 25 amp so at 125 amp it is 30 volt so 3750 VA so at 230 volt 16.3 amp with no losses, clearly there will be losses and inrush but that will vary welder to welder.

The old oil filled welders had a further problem, forgetting the dangers of the oil its self, the wires inside the welder were not insulated, the oil would rot any insulation, so it was important that the welder is not dropped as if it is the wires can bend an become too close to each other.

The safety cure is to earth, however if you earth, that earth must be able to take the welding current, I have seen many an earth wire melted due to welding, so in the welding bay every earth wire was 35 mm or larger, and the oil filled welding sets could only be used in the welding bay, one because protected with earth cables and two so no one could drop it.

However the modern inverter welders use a higher frequency so give a feeling of welding with DC, clearly not the 25/75 heat split found with DC it is still 50/50 but a very smooth output, they also have a far lower in rush, and they have replaced both the oil and air cooled welders.

The problem is the oil inside the oil cooled welders has to be got rid of using specialist firms, so there are many oil filled welders tucked into corners of buildings as it costs so much to scrap them, if they can gets some one to take one, they are rubbing their hands as saved the money that would need spending to scrap one.

They can today have safe oil in them, however until a sample is tested you don't know if safe oil or old oil, and it costs to get it tested, I know where I worked they were all drained and refilled with a safe oil, but they were not cleaned out, so safe oil all now contaminated.

As to if you can give away one of the old welders I don't know.

#### Devonchris

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The oil is more than likely PCB (Polychlorinated biphenyl) which is a carcinogen and, as Eric has mentionef above, is difficult and costly to deal with. However, in the spirit of being helpful in answers, here's what you need to do.

One method that can be used to reclaim PCB contaminated transformer oil is the application of a PCB removal system, also called a PCB dechlorination system. PCB removal systems use an alkali dispersion to strip the chlorine atoms from the other molecules in a chemical reaction. This forms PCB-free transformer oil and a PCB-free sludge. The two can then be separated via a centrifuge. The sludge can be disposed as regular non-PCB industrial waste. The treated transformer oil is fully restored, meeting the required standards, without any detectable PCB content. It can, thus, be used as the insulating fluid in transformers again.

Good luck

#### EricMark

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I have read about PCB's thought it was "particular crunchy bits" found in the fat from the fifth elephant when it landing on the disc world?

Still think best option is put it on free cycle and let some one else deal with the problem, and get a welding inverter instead.