Mauileaf wrote:Landlord comes into town tomorrow and is actually shocked about the 20a breaker with it being marked 50a

A little background from the National Electrical Code sounds like it would be helpful:

1) First, if you have a circuit with just a single receptacle on it, the only rule about the size of the receptacle is that it is at least as big as the circuit size. So there's nothing wrong with a 50 amp receptacle on a 20 amp circuit.

2) Second, welder circuits (Article 630) are a bit unusual. Because welders often have a duty cycle of less than 100%, you calculate a reduced conductor size. So a 50 amp welder with a low enough duty cycle might only require 25 amp conductors. Moreover, the small conductor rule 240.4(D), which says for example that #12 Cu shouldn't have a breaker larger than 20 amps on it, doesn't apply to some special applications, including welders. So you could use the full 25 amp capacity of #12 Cu for a welder. Lastly, the breaker can be up to 200% of the conductor capacity, so you could have a 50 amp breaker with #12 conductors on it.

3) Someone not familiar with the above or wishing to repurpose the circuit might have come along and replaced the 50 amp breaker with a 20 amp breaker.

Cheers, Wayne