Spot welder socket requirements.
 

One for any electricians on here. I have inherited a spot welder. It is currently wired (probably incorrectly) with a 13 amp plug. If I plug it into my sockets in the garage, it trips out the RCD at the fuse box. I have plugged it into the cooker socket in our kitchen, and it works fine. So, I guess that to use it in the garage I need a suitably rated (30 Amp ?) extension lead from the kitchen, or I need a specific spur with the correct current rating running off the fuse box in the garage (this currently has outputs with 5 and 15 A fuses on them). Any comments gratefully received.


Pete

A spot welder creates almost a dead short and thus draws a lot of Amps.
You need a dedicated supply for that.
Can be found in kitchen and also normally the geyser.
The unit can be a 380V unit, usually using two of three phases.
It will "work" on 230 but not correctly, so check specks.

If it is tripping the RCD, there is a 'leak' to earth (or an internal problem), may only be very small - sufficient to trip the RCD, but not enough to affect the operation of the welder.
The welder should have a rating plate giving the voltage and power, either in Watts or Amps (or both).

for each kw you will need 4 amp for the fuse

1 kw = 4maps
2 kw = 8 amps
3kw = 12 amps
not an exact but ok for household stuff

are you sure it is an RCD as RCD's don't trip on overload but an MCB does.

macafee2

I probably mean MCB - the switch on the garage outlet on the main fusebox/consumer tripped off when I operated the welder, but it was fine when I plugged it into the cooker socket, which is presumably on a circuit with a higher amperage allowance before it trips out. As you can guess , my understanding of electrics is fairly limited !

My current thinking is that my best option is to make up a suitable extension lead with proper 16 or 25 Amp sockets/plugs to run from the kitchen out to the garage- the garage wiring is obviously not up to the job.

Thanks

Pete

Pete, you really need to know a bit about the machine what it's rated at, 15 amps in the primary circuit say x 50 will give only 750 in the secondary circuit, and resistance welders usually require a 3 phase supply of say 100 amps per phase or 200 amps per phase, so 200 x 50 = 10,000 amps depending what you're welding in terms of material and thickness.

Typically the smaller units single phase for say clean 20 gauge to 20 gauge need a 30 amp supply and run at 3500 amps depending on timer settings etc.

Disclaimer : Just be careful and find out as much as you can about the machine you have before working with it.

What I've done in the past is clamp the two pieces to be welded drill say a series of 6mm or 8mm holes and fill the holes with mig weld works a treat, the result insn't bad either.

Just looking at spot welders on the Sealey website, and the two that they sell need to have a 30amp supply and therefore a dedicated 32amp round plug fitted. Not something that you would normally have at home.

With all electrical things, if in doubt consult a qualified sparky - don't want your eyes lighting up :eek:

What is the cable rating that is installed for the present garage supply?

It is probably the current surge which is tripping the mcb, rather than the sustained current. It might well be possible to change the mcb to either a higher current rating, or a more surge-tolerant type, or both.



Need to know:
- Fuseboard layout. I'll assume a 'master' rcd (the width of two mcb's) and individual mcb's per circuit. If not, say so.
- Rating of the mcb for the garage, noting if it has a prominent B or C on it.

- Cable size and rough length going out to the garage.

Thanks for all the responses folks- sorry for the delay in replying, I have been busy with other things over the last few days.

The cable to the garage looks fairly chunky (see picture) and runs for about 20 metres from the consumer unit/fusebox to the fusebox in the garage. The MCB on the garage 'spur' at the consumer unit is rated at 20A. The garage fusebox has four fuses - 2 rated at 5 A (lighting circuits) and 2 rated at 15A that feed the sockets in the garage through 2.5mm cables.
The welder seems to be rated at 25A for a 220/240v supply, with the short circuit (welding ?) current stated as 7000 A on the plate on the machine.

My mechanic at the local garage has borrowed the spot welder at the moment to put some sills on a Triumph TR6 - he says he could make me up an extension lead to run it of my cooker socket in the kitchen.

Can I change the MCB in the consumer unit to one rated at 30A, or will this be dangerous if the wiring to the garage is not up to the task ?

Cheers

Pete