Gentlemen, thank you all very much for your assistance and insight. It was all very good information. I found the answer to requiring a 20 amp circuit breaker while also requiring 25 amps available to that circuit in order to obtain the full output of the welder. As others have suggested, it's in the circuit breaker design and test criteria. The following is an excerpt from a circuit breaker manufacturer that explains the current carrying capabilities of most circuit breaker:
The CSA test program as well as our inhouse test program confirms compliance with the regulatory requirements by conducting the following tests:
Initial Trip time confirmation
* The breaker is "over loaded" to a value of 135% of the current rating and the breaker must trip within one hour.
* The breaker is then "overloaded to a value of 200% of the current rating and the breaker must trip in typically in less than two minuets.
Temperature test
* The circuit breaker is overloaded to a current value of 6 times the rating ( but not less than 150 amp.) and switched 50 times.
* The circuit breaker is then placed in a 40 deg. C. ambient temperature and forced to carry 100% of the current rating until the circuit breaker reaches thermal equilibrium. Temperatures are recorded and must be below the maximum temp. limits of the requirements.
Considering the welder's duty cycle it will operate at the 140 amps advertised by Lincoln so my previous assumptions were wrong.
