heavy duty 1ph welder

[ericmark]

Rule of thumb a welder gives out 25V at 25A plus another volt for every extra 25A.

So 100A at 13A, 125A at 16A, with a 175A needing a 23A supply.

Now the older sets also have a high inrush and spikes will rupture the fuse. But the newer sets with inverters are much smoother and some have some circuit to cut out when a rod sticks.

So although one can use a 150A inverter on a 13A fuse and often get away with it for the older types 100A is limit.

Over 175A twin or three phase is the norm.

The old Oxford oil cooled welders have in the main gone. There was the problem with PCB's in the oil. And second the earthing problem. The wires inside were un-insulated and if the unit is dropped they can bend and cause a short. This can connect the supply to output. So only safe way is to earth one of the outputs. However if this is done one can get welding current on the earth wires so the area where they are used needs 50mm earth wires to ensure they don't burn out. So normally hard wired so can't be used elsewhere. This has in the main resulted in the oil cooled welders being scraped.

Because DC gives a 25/75 split in heat and can use all three phases many commercial sets are now DC. It is also required for TIG and MIG. With the switch mode technology variable input voltages can be handled so one can get some really big sets. Air arc need around 300A and often one needs two sets to give output required and at 230V looking at a 50A supply for each set. Clearly these can't be used in a domestic premises.

In the older sets for example the BOC the iron core is racked in and out with an electric motor and if left in racked in mode often one can't switch them on without blowing the fuse. I have manually racked out the core many times.

The 16A supply in UK houses is a problem. The FCU is neat and easy to fit but the 13A fuse is just a little too low for many items from Ovens to Off peak heaters and includes welding sets.

With something like the welding set one wants the reset handy so the supply pods used with caravans are normally best option so the MCB in consumer unit is over the 16A.

However with the inrush often type C or D is required and this means often a problem with earth loop impedance. And of course this is a problem with DIY as very few DIY people have an earth loop impedance meter.

 

[SimonH2]

Fair enough, but an interesting restriction given that it allows 26A to be loaded at one point on the ring,

It is a fallacy that a double socket outlet is rated at 2 times 13 amps. The manufacturers give a maximum loading which can be ( depending on make ) as low as 18 amps total for the two sockets.

People might load it at 26 amps but very often this leads to the socket's terminals and / or internal connections being overloaded.

In which case, I'd question how on earth they justify such a restricted socket either fit for purpose or safe. Except for some fairly limited situations, it is not unreasonable to expect an average user to work on the basis that if they can plug a load (whether fan heater, kettle, microwave, pizza oven, washing machine, etc, etc, etc) into a socket than it's safe to do so. If it suits the user to have the kettle and a pizza oven side by side on the worktop, then they are likely to be plugged into the same double socket.

I know I'm not an electrician, but I find it hard to believe that an installation where that could be anticipated to cause damage is neither safe nor fit for purpose. We know that Mr/Mrs Average doesn't understand electrickery - that's why installations are designed so that they can't harm themselves, eg by having a fuse/CB that will turn off the supply if they plug too many fan heaters in at once*

* A friends girlfriend had her boiler break down during the cold spell in December. She went round borrowing all the fan heaters she could to keep the house warm. I had visions of her plunging the house into darkness** and suggested she not put them all on full.
** There is at least one ceiling light that doesn't work when a ring main fuse is pulled, I strongly suspect that the house used to be owned by Mr BIY

 

[bernardgreen]

In which case, I'd question how on earth they justify such a restricted socket either fit for purpose or safe.

There is definately a need for Mr and Mrs Average to be a bit more educated about the use of electricity in their house.

It is impossible to make any use of electricity 100% safe. There has to be a compromise.

The overloaded double 13 amp socket almost always fails in a safe mode. In the worst case there may be some smoke and maybe limited flames but provided it was installed correctly it is still acceptably safe. The live and / or neutral connections might fail but the earth connection remains intact. Protection in the CU ( if such protection has be fitted ) will still be effective against shock hazards.

There is no way to fully protect a user who is so stupid as to try and use a socket that is obviously burnt or otherwise damaged. Or someone who places inflamable material close to a power socket they are overloading

 

[SimonH2]

In which case, I'd question how on earth they justify such a restricted socket either fit for purpose or safe.

There is definately a need for Mr and Mrs Average to be a bit more educated about the use of electricity in their house.

It is impossible to make any use of electricity 100% safe. There has to be a compromise.

The overloaded double 13 amp socket almost always fails in a safe mode. In the worst case there may be some smoke and maybe limited flames but provided it was installed correctly it is still acceptably safe.

I think if you asked a random sample, very few non-electricians would see any problem in pulling 13A from a 13A socket, or 13A each from two sockets. It's within the restrictions any normal user could be expected to understand and is therefore not overloaded from the perspective of reasonable expectations of an average user.

There is no way to fully protect a user who is so stupid as to try and use a socket that is obviously burnt or otherwise damaged.

I never mentioned someone using an obviously damaged socket - I was talking about someone using a socket in a manner that I think you'd find the vast majority of people would consider reasonable. If the socket then fails, smokes, gets charred etc, without having been overloaded then I'd suggest it was either faulty (as in had a non-design defect) or was of defective design.

What next, a 13A single socket rated for 9A ?

 

[bernardgreen]

What next, a 13A single socket rated for 9A ?

Odd that you mention that because back in the 1970's or 80's the GPO Telephone engineering department issued an edict that no 13 amp plug was to be used for more than 9 amps within the GPO .

It came about following problems with burnt plugs and sockets. This effectively limited the load on a double socket to 18 amps.

There was one exception for two makes of plug (MK was one of them ) when used in a single socket ( again the socket had to be an approved make ) but the acception had to be applied for and was not automatically given. Other organisations had similar restrictions.

 

[flameport]

Are you saying that 2.5mm cable, or even 1.5mm cable won't carry 13A ?

No. However changing the flex to a size which is far too small will just lead to the wrong plug being fitted (the 13A one in this case).
Then after blowing the fuse a few times, someone will replaces the plug with another type, or even replace the fuse with a lump of metal.
The flex is now unprotected and will overheat the next time it is used.

It's the same reason why items such as widowmakers should never be constructed (a flex with a plug on each end, or a Y arrangement at the end of a single flex). The person making it may well say they will be careful / no one else will use it / it's in a locked cupboard and so on - but it is inevitable that someone else will get hold of it at some point.

 

[SimonH2]

What next, a 13A single socket rated for 9A ?

Odd that you mention that because back in the 1970's or 80's the GPO Telephone engineering department issued an edict that no 13 amp plug was to be used for more than 9 amps within the GPO .

It came about following problems with burnt plugs and sockets. This effectively limited the load on a double socket to 18 amps.

There was one exception for two makes of plug (MK was one of them ) when used in a single socket ( again the socket had to be an approved make ) but the acception had to be applied for and was not automatically given. Other organisations had similar restrictions.

Well that's interesting, but rather supports my argument that the products are defective in design. Clearly the GPO found that most 13A plugs/sockets were defective and thus chose to derate them for internal use. But that's a technically qualified group making a technical decision.

I still maintain that for the average man in the street, it says "13A" on it, therefore it should be capable of supporting a 13A load. If you have to rely on "educating the user" for such a simple thing, then you've failed totally. If it really isn't safe to use it for more than 9A then it should not be a "13A" plug or socket.

There is also the issue of where such a limitation might be stated. I've looked through a few catalogues over the years, and bought/fitted a few fittings. I have NEVER, EVER seen any reference to a current limitation such as you suggest - but there have been one or two where I have my doubts But even if such information is known to the system designer and/or installer, there is the matter that if you install them then you are building in a defect from the start since you have no way (in general) of knowing what the end user might want to use the sockets for in the future. The only way you could possibly excuse installing a 13A double socket that is not capable of carrying 13A on both sockets simultaneously is if either :
a) Due to the location (eg a socket in the back of kitchen cupboards that could only reasonably be used for fridge and freezer) it would be quite impractical to apply an excessive load
or
b) You explicitly label the socket with the limitation. If you did an install for me and I found sockets so labelled then I'd be instructing you to remove them and replace them with satisfactory items - and take you to Trading Standards if you refused.

And talking of Trading Standards, if a 13A device is not capable of carrying 13A, then does it comply with the standard (BS whatever) ? If it can comply with the BS and still not be suitable then the BS is a load of BS - but then I no longer respect the BSI since they demonstrated (IMO) not too long ago that they can be bought when someone with sufficient money wants a standard approving for them (look into Office Open XML to see what people things of ISO and their members now). But that's straying even further off topic.

 

[SimonH2]

Are you saying that 2.5mm cable, or even 1.5mm cable won't carry 13A ?

No. However changing the flex to a size which is far too small will just lead to the wrong plug being fitted (the 13A one in this case).
Then after blowing the fuse a few times, someone will replaces the plug with another type, or even replace the fuse with a lump of metal.
The flex is now unprotected and will overheat the next time it is used.

Clearly there is a balance to be found. But that is an argument for never doing a lot of things. Extend the argument a bit and you could argue that you should never make such a welder because someone could fit a smaller cable and smaller plug, and then replace the fuse with a bit of bolt - and so it's the fault of the welder manufacturer for making something that could be abused in that manner.
Incidentally, I have seen (on a farm years ago) what happens to those trailing 13A rubber sockets when you run a Pickhill Bantam oil cooled welder through them, with bolts in place of the fuses, and wind up the power. This one had opened up like a banana and had two "blobs" where there were once terminals on the ends of the live and neutral cores

Back to the original question, it does all depend on what he intends doing with it (and bearing in mind we still don't know any details other than it "has a big cable"). When we bought a large MIG welder* it had a 32A plug on it, but needless to say neither of us have a 32A socket to hand. My plan was to leave the 32A plug on it and make an adapter to allow it's use with a 13A socket since that's all we actually need (and an adapter to a 16A plug since I have a 16A socket by the bench just for dad's old stick welder). I have the bits here, but before I got it done, my mate managed to get the cable into a 13A plug - which was an impressive feat. Yes it does work, and no it doesn't have a bit of bolt in the plug. But we both understand that we won't be able to wind it up and do what we could do when it was in another mates workshop on a proper supply.

* A friend had to close down his business, and between us, myself and another friend bought a fair bit of his machinery & tools.

Also stepping back a bit, it's been stated that it's not allowed to fit a 16A (with local overcurrent protection) or 32A socket to a ring main. It could be argued that this is in fact one of those rules (like a lot of Part P) that has negative consequences. I can see there are some design considerations (specifically ensuring that it's not going to put most of the current down one short leg if the socket is near one end of the ring) with a 32A socket, but there is no such problem with a 16A socket. So you have a situation where the regulations prohibit something that isn't a safety issue, in favour of something that is - in this case, providing an incentive for people to run a fair sized welder from a 13A socket because of the cost of getting a dedicated supply installed. In our house, getting a suitable cable direct from the main DB would be a right pain, and not everyone has a submain and DB in their garage - heck, in my flat the cheapskate leccky** couldn't even be arsed making the garage sockets into a ring main
Of course the third option is that (and again it's something Part P encourages) the keen DIYer simply ignores the regs and connects a 16A or 32A socket to the ring anyway - oblivious to any design checks that might be required.
** Note I specifically differentiate him from the quality end of the trade, before anyone here takes offence.

PS - what's the current carrying capacity of a 2.5T&E, under typical domestic installation conditions, when under an intermittent load such as a welder ?

 

[CustardPTT]

Hi Ericmark,

You said....

In the older sets for example the BOC the iron core is racked in and out with an electric motor and if left in racked in mode often one can't switch them on without blowing the fuse. I have manually racked out the core many times.

</soundOfPennyDropping>

I've a BOC 185amp set, how do you manually rack the cores back in? Err, no reason, just curious </soundOfBreaker>.

Also, another thing to consider when calculating the cable required by duty cycle. Big welders pass quite a lot of current even when not welding.

Cheers

Pete

 

[SimonH2]

433.1.5 only allows BS 1363 accessories to be supplied by a ring final.

Sorry, if you didn't know this by now, I'm something of a pedant

Actually, 433.1.5 does NOT say that only BS1363 devices may be supplied by a ring final. It says that they can, and specifically overrides the restrictions of 433.1.1 - allowing* a ring final wired in 2.5mm which is too small to meet the requirements of 433.1.1. Yes, I've now been able to look up what it actually says.
* But not universally

Saying that <something> is allowed, is not the same as saying that <anything else> is not allowed.

So my interpretation is that if you downgraded the RCD supplying the circuit to 20A so that 433.1.1 was met for every conductor - then it would be legal to wire a 32A, or 16A with local overcurrent protection, socket to a ring final. Not the best way since you'd be derating the whole ring, and would be liable to nuisance tripping with a large welder - but if the main distribution board is not located where it's easy to run an extra circuit, then it would be an option.

Have I missed something else ?

 

[Stoday]

Wylex used to sell non standard plugs and sockets for ring finals. I guess they did not comply with BS1363.

The Wylex plugs came in 5, 10 and 13A versions. The pins were different, not just the fuses. All three could be plugged into a 13A socket; only 5 and 10A into a 10A socket and so on.

Some plugs had an integral extension socket on their lids so you could add a plug to a plug.

Better made & thought out than the standard 13A socket, but the proverb about building a better mousetrap never was true.

Untitled

• Stoday
• 9 Feb 2011
• 1

 

[SimonH2]

Wylex used to sell non standard plugs and sockets for ring finals. I guess they did not comply with BS1363.

But then this would have been before 17th Edition - dunno what earlier editions said.

The Wylex plugs came in 5, 10 and 13A versions. The pins were different, not just the fuses. All three could be plugged into a 13A socket; only 5 and 10A into a 10A socket and so on.

Some plugs had an integral extension socket on their lids so you could add a plug to a plug.

Better made & thought out than the standard 13A socket, but the proverb about building a better mousetrap never was true.

Untitled

• Stoday
• 9 Feb 2011
• 1

Ah, those were the days. Back when I was an apprentice in the local shipyard, most of the sockets/plus were the old D&S round pin ones where the live pin was a screw in fuse. The story was that they kept using these as it made it not worthwhile nicking the plugs as they wouldn't fit 13A sockets ... the story also added that it was rumoured that most houses in the town were wired with D&S sockets

I recall they had an "interesting" fault mode. The live pin was a screw in fuse (threaded stud on one end) which probably seemed a neat idea - fuse easy to change, you can always see the rating etc. However, the fuse could work loose, and then you were left with a live pin sticking out of the socket
Can't find a photo of the plugs, but it's mentioned in Wikipedia.

But I think this thread is drifting somewhat off topic now.

 

[ban-all-sheds]

There was the problem with PCB's in the oil.

"Shell Diala Oil B does not contain PCB's"

 

[ban-all-sheds]

in my flat the cheapskate leccky** couldn't even be a***d making the garage sockets into a ring main

He was planning ahead, and providing you with a circuit to which you could add BS EN 60309 outlets.....

 

[ban-all-sheds]

Actually, 433.1.5 does NOT say that only BS1363 devices may be supplied by a ring final. It says that they can, and specifically overrides the restrictions of 433.1.1 - allowing* a ring final wired in 2.5mm which is too small to meet the requirements of 433.1.1. Yes, I've now been able to look up what it actually says.
* But not universally

Saying that <something> is allowed, is not the same as saying that <anything else> is not allowed.

In this case it is, because it's an exception. 433.1.5 describes the exception to 433.1.1.

Taken together, what they say, in effect, is "All circuits shall comply with 433.1.1, but if you have a ring final circuit with this sort of cable and that sort of protective device and if the cable is installed in one of these ways and if when used as intended it's not likely to be overloaded anywhere for long periods then you may use it to supply BS 1363 accessories."

If you have a ring final which complies with 433.1.1 then you may use it to supply anything.

If it does not comply with 433.1.1 and it does comply with 433.1.5 then that's OK.

If it does not comply with either 433.1.1 or 433.1.5 then you're on your own. You may be able to demonstrate that your circuit still complies with the fundamental principles, and that the departure from Regulation 433.1.1 is allowable, but if push came to shove I think you'd need more to back up your assertion than "there's not much difference it ought to be OK"

So my interpretation is that if you downgraded the RCD supplying the circuit to 20A so that 433.1.1 was met for every conductor - then it would be legal to wire a 32A, or 16A with local overcurrent protection, socket to a ring final.

Absolutely, because then you would not need an exception from 433.1.1

But as you recognise, you would have thrown away the reason for having a ring in the first place, namely the ability to use 2.5mm² cable on a 32A breaker.

Not the best way since you'd be derating the whole ring, and would be liable to nuisance tripping with a large welder - but if the main distribution board is not located where it's easy to run an extra circuit, then it would be an option.

A better option, depending on the installation method for the cable and the range of MCBs available might be to turn it into a 25A radial.