ECN Forum Forums Code Related Discussion Canadian Electrical Code Topics mig welder

The same thing that prevents a home owner from plugging in two 1500 W hairdryers into the same 15 A recepticle circuit.

Larry

What will stop the customer from plugging in a full size welder is that the breaker will trip. That's what breakers are for.

If you install #6 wire, you will use a 30 amp breaker to protect the welder. You can't fuse equipment rated for 20 amps at 50 amps. If someone plugs in a full size welder, the breaker will trip.

The comparison is a range plug. They are rated for 50 amps and are commonly wired with #8 (45 amps) and fused at 40 amps. If someone plugs in a larger range, the breaker trips.

There are several items I want to speak to besides the welder itself.
First is the reference to breaker size in section 8 or the match in section 26.
Sections 2m, 4, 6, 8, 10, 12, 14, 26 and 30 are basic code sections that generally apply to all installations. For example section 10 tells us the rules for bonding and grounding that apply across the board to installations under 750 V. Section 36 only applies when the voltage is above 750 volts and you better know the rules for grounding are very different there. Section 36 is amendatory.
welders are wired according to all sections outlined with specific rules that are applicable to welders. These rules ammend the requirements of section 14 and 4 with regard to wire size and protection. So if section 14 might require a 30 amp breaker and #10 but the welder was rated to only need a 20 amp breaker and #12 then the ammended nature of the section over rules the other two sections.
The range example is a good one as the wire can be bigger than #8 if the range is rated higher than 12 KW.
We might need #6 if the range is bigger than 12kw. You may be a chef with a 18 kw range from 8-300 that wire is based on 12 kw plus %40 of the rating in excess of 12 kw
8 KW plus 4kw * .4 = 9.6kw / 240 = 40 amps *1.25 = 50 amp breaker and 40 amp wire. If the range was 20 kw then the breaker, wire and receptacle would all have to be upgraded to a larger size. We can see the standard range wire and receptacle covers a broad range of stoves (pun intended)
In answer to this welder question the name plate and duty cycle are essential to matching the two.
Start with 42-006 and the nameplate. Wire and breaker according to 42-008 and you are on track.
The unit comes with a plug of certain configuration I assume was evaluated to the standard for transformer arc welders. There is no requirment to wire to the plug if it is for a welder as section 42 allows the match as an exception to other rules in earlier sections. Now if the plug was to be used for another load that is not a welder you could have another problem if 1 load uses a different set of rules than welders