Spot Welder

[pughd]

I have recently purchased a spot welder (I am currently restoring a classic car)

The electrical installation states that the plug should be greater than or equal to 16A (so I assume industrial plug/socket is needed), the circuit breaker 20A and it should be fused by a 16A delayed fuse. I have never heard of delayed fuses what are they?

The instructions go into great detail but negated to state the amps. I am assuming that the unit will pull just under 16amp as they didn't recomend a 15A circuit breaker or am I missing something here?

Dave

 

[Lectrician]

I don't know where the 20amp bit comes from.

I would say a C or possibly a D type MCB rated at 16amp would be fine. You could use a 20amp, and this would still be fine, and comply.

I would use a BS4343 CEEFORM socket outlet.

You need to ensure the cable is sized correctly for the current and volt drop, and also sized to ensure a low enough earth loop impedance when using devices such as C and D type MCB's

An RCD may also be required.

I would recommend an electrician install and test the circuit for you.

 

[Stoday]

You bet they didn't mention the amps!

Spot welders (other than cheapo toys) pass high current for only a few cycles. You don't need a circuit that meets the current requirement continuously.

Same thing with your computer. It will take a switch-on surge of around 80 amp but you still run it from a 13A plug.

Unlike the computer, a spot welder will take the high current for a good deal longer (but still less that a second). You have to go with the manufacturer's recommendations unless you have the gear to do some testing.

Delayed fuses will allow a high current transient but will blow on sustained overload. You might be able to use a mcb, but I'm sure the usual type B would not do. Again, you have to seek the manufacturer's advice.

 

[dw3101]

I have a spot welder so can advise you here

A 16A industrial socket with a 20A Type C Breaker using 2.5mm t&e (depending on distance) 4.0mm if you want overkill.. will be fine.

They WILL NOT run from a 13A Plug without blowing the fuse.. (i know as mine came with a 13a plug on it previous owner tried.. impressive as to how they got the plug on!

I actually use a 32A plug on mine as my sockets also power my 230A mig and my 200A AC/DC tig.


The actual contacts (copper bars are nearly an inch in dia and get hot!! - 2000 - 3000A iirc.. at 2 - 3v)

One tip is clean the metal on all 4 edges.. get it very close together and then spot weld it.. also I would use a weld through primer so you can prime the inner 2 edges.

Also drilling the panel and using self tappers to hold whilst alligning helps.

Also if you have a timer... wind it to max!!!

David

 

[pughd]

Thanks for your replies and even for the advice on use of the spot welder .

I currently have an old cu with plug in MCB's, with a couple of spare slots. There is no external isolation switch between the meter and cu. The electrical installation doesn't seem that old to me, when did they start using RCD + modern cu. I am guessing that the house was rewired in the 1980's. It has an inspection label dated 1988.

My garage is not an outbuilding and is connected to the house, approximately 3-4m from the cu. Any wiring would be through the roof space above the kitchen and down the garage wall for about 1m. My intention would be to use 4mm cable.

I have been browsing the internet and have been unable to find any type c MSB's for plugins, do they exist?

If not, I wonder if there is a configuration that I could still use a slot in the old cu and may be put a new small cu with type c msb +rcd in the garage to service the welder. I am assuming that I can't use a type b in the old cu, as this would trip.

Dave

 

[plugwash]

if you board has a 100A incomer then you can fit a B40 and then fit a C20 seperately after it for overload (in a modular box or whatever)

if not then the most you can fit is a B30 or B32 (not sure which one current plugins are) This might be ok it might not its a bit of a close call

failing that its time for a new CU

 

[pughd]

The cu is 100A, so I can use a B40.

I guess with this configuration there is still a chance that the B40 will trip when using the spot welder.

I will try this, if it trips it's new cu time.


Dave

 

[SwindonSpark]

Lectrician wrote:

I don't know where the 20amp bit comes from.

On-Site Guide Appendix 8 (page 153)
Final radial circuits using 16A socket-outlets complying with BS 4343 (BS EN 60309-2) (Industrial Sockets)

"The overcurrent protective device is to have a rating not exceeding 20A"

 

[plugwash]

The cu is 100A, so I can use a B40.

I guess with this configuration there is still a chance that the B40 will trip when using the spot welder.

I will try this, if it trips it's new cu time.


Dave

A B40 and a C20 should have about the same fast trip response so it should be fine

you need the C20 downstream of course to give you overload protection

 

[dw3101]

I just use a type b 20A breaker first and see what happens, my compressor is the only thing that needs a type c.

My welders dont have a problem.

David

 

[Lectrician]

Lectrician wrote:

I don't know where the 20amp bit comes from.

On-Site Guide Appendix 8 (page 153)
Final radial circuits using 16A socket-outlets complying with BS 4343 (BS EN 60309-2) (Industrial Sockets)

"The overcurrent protective device is to have a rating not exceeding 20A"

I would say a C or possibly a D type MCB rated at 16amp would be fine. You could use a 20amp, and this would still be fine, and comply.

I am fully aware of that, thanks. BUT the welder doesn't have to be connected via a plug and socket, so I was wondering why the install instructions say to use a 20amp.