Power supply ideas

[secretsmoker]

Hello again,

I am very happy so far with the little Xcalibur Eurostar I picked up last week, however the power supply is becoming a bit of an issue. I realise this has been covered quite a lot in the forum but I am still a bit perplexed as to how I am going to sort this out without spending a fortune!

The supply will probably need to be uprated eventually but the main issue is that the garage supply and house central heating are on the same circuit. I seem to be fine welding at lower power when the heating isn't on but I trip the RCD every few welds when it is. The lights and electric door in the garage run off the same circuit too so the first few times it happened I found myself in the pitch dark under a car with no torch and a phone that had run out of battery!

Comedy blunders aside I am now being a bit more careful with regards to extricating myself WHEN it next happens as I am not going to have the means to get this sorted out any time soon. The garage is a fair distance from the house so I am hoping that the cable used is fairly thick but I haven't thought to check on this yet. More newbie issues I realise. I will probably figure this issue out eventually if you folks are bored of replying to these threads!

If someone could perhaps list the things I will need to get sorted out I can then put it to our regular electrician and see what he says.

The moral of this story I suppose is when welding at home always make sure you have a means of escape and a torch handy (preferably on your person at all times)

 

[rtbcomp]

RCD or MCB ?

 

[secretsmoker]

Actually it's an MCB (getting my acronyms mixed up sorry) rated at 16A I think from the code. This one circuit does the garage and the central heating. The mains switch says 100A. I will go and try to figure out what else there is in the circuit as I think there may have been another older fuse box where the circuit branches off...

The house is quite old but the garage is quite new so I am hoping it might have some decent cabling. Other problem is the garage is around 15m of cable away from the circuit breaker I would think.

 

[KemppiFrog]

Have a peek in the box. Just because the garage is new, doesn't mean the supply is enough to weld.
I have a 6mm section wire to my w/s at around 25mt from the board to the welders. 20 amp fuse, and the only time it gives trouble is when I use the cut off saw (a brief 45(!) amp on start up.
Central heating usually requires very little power,so I suspect small cables and welder power surges are the problem.
KF

 

[secretsmoker]

Hmm I was afraid of that! The cable at the garage end looks fairly thick but I suspect the problem lies with ancient wiring up to the cental heating which looks considerably thinner. Was hoping a cheeky swap for a bigger ampage on the circuit breaker may have been OK but I suspect that would be a bad idea with the ancient wiring in between!

Cheers for the input. Probly going to need some fairly extensive rewiring at some point. Will see how I go as all the work I am doing from now on should be on lower power. Hopefully I will get fewer burnbacks as I improve. The things that caused the fusing were mostly building up brace bars with brackets to weld in to the door aperture using higher settings. Now that is all sorted I am back to chopping up the MX5 again!

 

[madkayaker]

A sparky that knows what there doing would be first on my list. It's quite normal for heavy inductive loads (what a welder is) to trip MCB's due to the high inrush current when the trigger is pulled. You might be able to change the type of MCB to one that will tolerate the inrush current better. It's impossible to tell if that's safe to do without testing the circuit.

 

[secretsmoker]

Didn't even realise that might be an option, very helpful. I will have a word with our electrician, luckily he is around soon to do some stuff to my sister's house.

The guy has been in the game for years so I doubt this will be the first time he has encountered this type of thing. He has done most of the rewiring in the house and is always reputable from our experience so he should be able to give me an answer straight away I would imagine.

Once again thank you so much for all the help chaps. Dare say I would be scratching my head for ages without the answers I have found here so far!

 

[madkayaker]

I would recommend fitting an RCD as well if there isn't one

 

[normspanners]

When you say central heating is it poss that the immersion heater in the domestic hot tank is also run off this? because that can a large load cutting in whenever it feels like.

 

[secretsmoker]

In this case the heating and hot water are all one unit with big storage tanks so no separate immersion heater in the house. This can be a bit annoying when the water in the tanks runs out and the heating is off as it doesn't always kick in as it's supposed to!

I have checked and the only things on the circuit are the heating unit itself and control box. After that there is a long cable down to the garage which normally just has lighting and door control unit minus anything that is plugged in to the sockets.

Hoping to be able to speak to our sparky this week to ask about solutions that won't require too much rewiring (I was a bit shocked at the cost of cabling nowadays!) as looking at it I think the narrow gauge cabling to the heating is the likely culprit!

 

[anjum]

The narrow gauge cabling to the heating circuit is not likely to be the problem, as it will not cause the heating circuit to draw ant more current from the MBC.

What do you mean by "after that"? is the garage wiring taken to the mcb or spliced in later at a junction box or similar? If so, that bit of wiring will need changing at least, not for the tripping problem but for safety /overheating issues.

If there's space in the fuse box then adding an extra MCB for the garage with the correct MCB for the cable size is the best solution. There are, IIRC, different sorts of mcb designed to give different surge characteristics.

If you have to run new cabling to the garage use the thickest cable that you can afford to allow for future additons to your needs e.g. plasma cutter. You may be able to put an extra cable in parallel with the existing one to save costs.

 

[secretsmoker]

I need to use my words more! Sorry by 'after that' I mean the that from the MCB there is around 15 ft of cable towards the heating. There is a very old school looking junction box which looks like it also holds a fuse just before the heating unit connects and the garage supply is spliced in from said box.

Needless to say I hadn't really considered this at all in my initial excitement in getting the welder but like you say I think this probably needs looking at as a matter of urgency as it was clearly never designed for this sort of usage!

Taking a seperate feed back to the circuit breaker is going to have to happen as soon as I can get it sorted out. Luckily I am still in the preparation stages chopping rust and making panels so I may not need a reliable welding power source properly for another week or so. I managed to finally get my door bracing in so I am happy to finally be making some progress!