Spot welder socket requirements.

EastPete · 15th June 2018, 12:12

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

kaiser · 15th June 2018, 12:47

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.

raykay · 15th June 2018, 13:36

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).

macafee2 · 15th June 2018, 14:13

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

EastPete · 15th June 2018, 14:32

Quote:

Originally Posted by macafee2

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

rustymotor · 15th June 2018, 15:33

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.

humphshumphs · 16th June 2018, 10:22

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

KWIL · 16th June 2018, 10:30

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

impvan · 16th June 2018, 13:25

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.

EastPete · 19th June 2018, 13:30

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

15th June 2018, 12:12	#1
EastPete Posted a thing or two Rover 75 CDTi Classic saloon, MGB GT, Skoda Yeti Join Date: Aug 2008 Location: Ramsey, Cambs Posts: 1,874 Thanks: 626 Thanked 635 Times in 430 Posts	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

15th June 2018, 12:47	#2
kaiser This is my second home 75 Tourer 2.5 Auto, 1.8T, 75V8ZT Join Date: Jun 2007 Location: Johannesburg ZA Posts: 6,200 Thanks: 1 Thanked 859 Times in 613 Posts	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. __________________ Worth his V8 in gold

15th June 2018, 13:36	#3
raykay I really should get out more....... Now Other Manufacturer Join Date: Nov 2006 Location: Co. Kerry Posts: 2,786 Thanks: 16 Thanked 310 Times in 283 Posts	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). Last edited by raykay; 15th June 2018 at 13:47..

16th June 2018, 10:22	#7
humphshumphs I really should get out more....... No longer a Rover Owner Join Date: Jan 2011 Location: As far east as you can go in the UK and not get wet feet. Posts: 2,273 Thanks: 404 Thanked 309 Times in 246 Posts	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 __________________ Richard. No longer a 75 owner as my tourer made it to the moon, and died on it's way back. But 1/4 million miles ain't bad.

15th June 2018, 14:13	#4
macafee2 This is my second home Rover 75 Saloon & Tourer Join Date: Sep 2012 Location: Lincoln Posts: 14,926 Thanks: 1,630 Thanked 3,032 Times in 2,181 Posts	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

15th June 2018, 15:33	#6
rustymotor Posted a thing or two Rover 75 Tourer Join Date: May 2017 Location: Hull Posts: 1,848 Thanks: 216 Thanked 432 Times in 340 Posts	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.

16th June 2018, 10:30	#8
KWIL Precise Rover 75 Tourer 2.5KV6 Connoisseur SE Join Date: Mar 2013 Location: Fleet Posts: 2,954 Thanks: 630 Thanked 617 Times in 480 Posts	What is the cable rating that is installed for the present garage supply?

16th June 2018, 13:25	#9
impvan Avid contributor ZT-T Join Date: Aug 2012 Location: In the trees, near Caernarfon... and frequently Aberdeenshire, and sometimes Romania.. Posts: 143 Thanks: 5 Thanked 36 Times in 29 Posts	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.

19th June 2018, 13:30	#10
EastPete Posted a thing or two Rover 75 CDTi Classic saloon, MGB GT, Skoda Yeti Join Date: Aug 2008 Location: Ramsey, Cambs Posts: 1,874 Thanks: 626 Thanked 635 Times in 430 Posts	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