Welder and extensions

[Anderzander]

A basic question but my garage is at the end of the garden and opens into a yard beyond that ...

So on my last 90, when I welded on my cross member, it was effectively at the end of a 100' extension - and the decrease in power was noticeable.

Is there anyway round that ?

My welder is a basic Clarke 100 mig and it was at the limits of power on that much lead.

It's not very practicable to up the cable size to the garage - but would simply getting a more powerful welder work ? Or would I still be limited by the length and size of cable ?

[Team Idris]

Bigger welder might be worse. It's voltage drop that is the problem and it can make the current go up on the cable on pressure washers, but not so much on welders I understand. The fix is a 4mm area extension cable.

[robertspark]

Its a cable size thing, all cable has a resistance, which in turn leads to a voltdrop, so, longer cable bigger voltdrop

You need a either a 4mm extension lead cable or (probably in contravention of the electrical regulations....) you could parallel up two extension leads with some careful thought.

Parallel cables are not that uncommon as it's a practice used both for cost (cheaper sometimes to buy two of the size below the one required) and sometimes you cannot get the bend radius or the force required to get the bend radius on the bigger cable or a manpower thing of handling a big cable.

Just an extension lead thing may not be be cleverest idea, but if you were doing it to get you out of a hole it's something that could be considered as a short term fix it you've got two extension leads already, why go and make up a third or source a third one.

[Anderzander]

Thank you both.

The wiring from my Consuner Unit is just 2.5mm2 to a waterproof junction box on the outside of the house. From there it's more 2.5 to the garage mini consumer box and again onto the garage sockets - and from there it's whatever extension I have.

I do have some chunky armoured cable I was going to replace the outside run with - though I didn't know what merit it would have without having 4 mm2 inside ...

Replacing the wiring inside the house is not something I'm ready for - it's bad timing for opening the walls and pulling floors up.

But I guess providing the RCD ratings are right for the smallest cables current carrying capacity - then upping the cable sizes on the other lengths would still go towards reducing voltage drop ? As I'd be reducing resistance over that part of the circuit at least.

Apologies for my ignorance !

[robertspark]

Sounds like you have a complicated daisy chain arrangement.

If you change the outside section to a thicker cable, it will basically reduce the voltdrop (i.e. you'll get more voltage for the same current draw, or more correctly you'll get more electrical power (Watts / kW) at the end of the cable). You can't change the RCBO (RCD + MCB) as the MCB will be rated to the current draw of the smallest cable in it's radial configuration (same size cable in a ring arrangement gets a higher MCB as current is split two ways), however if you change all of the cable from the internal MCB (or RCBO) to the external / remote distribution board, you can upgrade the MCB (or RCBO) to a higher rated trip device, given that the remote distribution board will have it's own circuits and each of them should have a correctly sized MCB / RCBO corresponding to that cable / circuit rating.

Basically all cable has a resistance that is related to not only the diameter of the cable but the temperature rating of it's insulation (given if it gets too hot, the insulation will melt), and also how many adjacent cores and it's installation method (is there a bunch of them together, is it in the ground, in conduit, or on a cable tray freely suspended to cool from the air directly. Temperature of the cable is key as that is what gives the cable it's continuous safe rating [not for house wiring but you can draw more current than a cable is rated for for a short duration, an example of this is jump leads / startermotor leads on a vehicle].

Then there is the voltdrop which is related to the current being drawn through the cable, and the total cable length (given electrical mains cable has a total allowable voltage drop from the source (electric meter in simple terms) to each of the outlets under a diverse demand (in simple terms, just because appliances have 13Amp fuses doesn't mean they run at 13A all of the time... [common schoolboy error very common in practice, but getting actual electrical loads is akin to finding rocking hose poo])

I seem to have stumbled across the IET (what long time ago was the IEE) wiring regulations cable tables on the net: http://www.batt.co.uk/products/category/136/Current-Ratings-&-Volt-Drop

A quick check of the tables indicates that for flex, you're probably looking for TABLE 4D2A (note / caveat... no longer my day job, so I'm out of touch a bit, welcome to be corrected, no offense taken, any guidance is better than no guidance?)

For armoured cable TABLE 4D4A (again I've been out of touch with this for a while, so willing to be corrected).

A really good book if you're interested in this in detail are the book series by Brian Scaddan, seems another quick search of google has revealed one of his books posted, I'd suggest a good bedtime read of the guidance before you attempt wiring anything if you're not 100% confident, (warning to others electric bites and it can kill, plus you can't see it, and technically a garage is a an area that requires building regulations approval (notification) for works (Part P) or work undertaken and certified by a Part P competent electrician. (i.e. you can do the work yourself, but you need to make a building regs application, pay your (think £75) and then they will inspect the installation and or get someone else to certify [i think that's how the "self cert" works now at least].

But, knowledge is power, and being better informed means you can make an informed choice or understand what others may be advising you.

Rob

[Hybrid_From_Hell]

I'm on single phase

300+ Oxford Mig 220 amp a dc tig

Run on a dedicated 3 amp supply from armoured cable to rcd box ...6 mm twin and earth from box to the big single phase plugs. Ext is a 6 mm 3 core same plugs.

Made a masoooovie difference to 2.5 T & E..

Size matters lol

[robertspark]

Run on a dedicated 3 amp supply from armoured cable to rcd box ...6 mm twin and earth from box to the big single phase plugs. Ext is a 6 mm 3 core same plugs.

32 amp I suspect

I have a dedicated (radial) 16Amp supply (given the plug is 16Amp rated, blue round one) that allows me to plug in my TIG, MIG and Plasma, and it does not afect the compressor (3hp / ~2.2 kW + a bit) and the electric heater (3kW) that may be running at the same time on the ringmain circuit.

[Anderzander]

I just have a single spur to feed the garage as a whole - it's 20 amp RCD on the house consumer unit (an unused feed for a power shower) - and that feeds to another small RCD unit in the garage with a lighting circuit (2 strip lights) and a socket circuit (2 double sockets).

[nickwilliams]

would simply getting a more powerful welder work ?

Team Idris is right that just getting a bigger welder may be worse, but if you've got the dosh to invest in an inverter based MIG instead of a transformer based machine then it can compensate for a low voltage input to some extent.

It's also worth being aware that the contact resistance in multiple circuit breakers and plugs and sockets in series (and especially the resistance of the 1in cartridge fuse in a standard 13A plug top) may well be significant if you want to sqeeeze every last possible drop of juice out of your extension lead. One long 2.5mm sq extension lead with a 13 A plug at one end and a blue 16A plug/socket at the other end will be better than multiple '13A' leads plugged in a chain.