Over sizing the breaker question?

[performance]

There isn't a certificate of occupancy permit for private residences after a structure is built in many states...At least not in this one. IF the correct plug is used, then it will be obvious, since the 6-50 is the only standard plug for single phase 220V welders and cutting equipment. The camper won't plug in.

[kenwhite]

The thing you have to consider when looking at the duty cycle, is that while the continuous current limit may be exceeded for short periods of time, the average current based on the duty cycle load is typically much less than rated continuous current.

If the branch has multiple loads, the breaker would still trip trip if severly overloaded when multiple loads are being used - normally a thermal breaker is specified for this type of circuit.

Article 630 is really written for commercial/light industrial use with exceptions for residential/home use of a welder.

[kenwhite]

Oh, and one other thing.

Just because a certain welder draws X# of amps, this does not mean that a certain AWG wire needs to be installed.

There are many factors that I listed in post #6 above that actually determine the size and type of cable that must be used.

Insulation type is also very, very, important when determining where the run can be placed and how much of the cable's ampacity will have to be derated...

EDIT: As Mark stated in his first post, if your are not comfortable doing all or part of the wiring upgrade, hire a competent electrician to either do it for you, or help you do it...

[ASE_MasterTech]

OK, I'll rephrase..
Here in the northeast most states I know require a 'Certificate of Occupancy' (& the accompanying inspections) be issued for any incoming occupant, be it renters-leasers-owners, commercial or residential. Structures/buildings are required to meet or exceed the code requirements in force at time of construction or most recent renovation, excluding 'fire code' issues which must be up to date.
Here in NJ, after owning 4 homes, 2 Amoco Service Stations, & currently working for Government, I can tell you that 6awg has been required on any 50amp outlet circuit I installed or had installed. This is 'code' here regardless of NEC recommendations, & IMHO just good common sense for wire buried in a wall or conduit whose future use may or may not involve a 'protected' or 'limited duty' device..

[A/C Guy]

The thing you have to consider when looking at the duty cycle, is that while the continuous current limit may be exceeded for short periods of time, the average current based on the duty cycle load is typically much less than rated continuous current.

If the branch has multiple loads, the breaker would still trip trip if severly overloaded when multiple loads are being used - normally a thermal breaker is specified for this type of circuit.

Article 630 is really written for commercial/light industrial use with exceptions for residential/home use of a welder.

If a branch has multiple loads, the breaker size should equal the sum of the loads with the appropriate wire used. If the breaker is tripping as in your statement, then the wrong supply wire and breaker was installed. We install multiple appliances on a single circuit regularly for commercial buildings. We use a larger supply wire on that circuit and the larger breaker equal to the sums of the maximum of the appliances and each appliance has it's own individual fused disconnect with the appropriate size fuses for that one appliance.

[kenwhite]

If a branch has multiple loads, the breaker size should equal the sum of the loads with the appropriate wire used. If the breaker is tripping as in your statement, then the wrong supply wire and breaker was installed. We install multiple appliances on a single circuit regularly for commercial buildings. We use a larger supply wire on that circuit and the larger breaker equal to the sums of the maximum of the appliances and each appliance has it's own individual fused disconnect with the appropriate size fuses for that one appliance.

Well, there are mimimum requirements for branch circuit design as well as load duty cycle, demand factor, requirements.

I never said the breaker would trip excessively, I said it would still protect the branch correctly even when overloaded with many circuits on the branch energized at once.

The rest of your post reinforces my previous points...

[Canada]

I can think of only one anwser to this post:

"There is never time to do it right but there is always time to do it over!"

[ASE_MasterTech]

I can think of only one anwser to this post:

"There is never time to do it right but there is always time to do it over!"

There's not always time to 'do it over', particularly when your house/shop is a pile of ash.
just a thought...

[ASE_MasterTech]

IF the correct plug is used, then it will be obvious, since the 6-50 is the only standard plug for single phase 220V welders and cutting equipment. The camper won't plug in.

This may have been the case previously, but a 'standard' is not a rule, & with the emergence of multi-voltage welders/cutters this 'standard' is disappearing.
The Miller Dynasty 200DX's we have on the job are voltage sensing from 110v to 220v & as so are equipped with a neutral (4 wires out of the machine). We wire the machine with a 30amp 4 pronged plug & then run adapters for the 220v-30amp/110v-20amp outlets we may encounter when moving from area to area.