i was just reading another topic from another forum about having 2 30a 220v receptacles on one circuit (welder and compressor) on one 30 amp breaker.(not being used at the same time0).Is this a safe practice? To my knowledge this shouldnt be done regardless if you dont operate at the same time....what do you think?
And no, over-all I don't think it a safe or wise practice. There is no guarantee of only one in use at a time. One device cycles automaticaly, the other is a welder. See 630... Although a welder is intermitant, and it is allowed to have multiple welders on the same circuit the OCP and wire size rules are expanded, and differ slightly from a normal branch circuit.
Without knowing the data plates and circuit particulars, I would say, no.
Mark Heller "Well - I oughta....." -Jackie Gleason
All of us install multiple receptacle outlets on 15 and 20 amp circuits all the time with no idea at all what will be plugged into them.
Why would this practice suddenly become unsafe once we move to 30 amp circuits?
Article 630 gives us some options for saving money when supplying welders but we do not have to use those options, we can supply a welder with a 30 amp cord cap with a 'standard' 30 amp branch circuit.
I see no NEC reason not to do this, it in my opinion is a design choice.
If the person paying the bill tells me they are fine with one circuit I would have no problem supplying them with one circuit once I explained the circuit may trip if both units operate at the same time.
Bob Badger Construction & Maintenance Electrician Massachusetts
Assuming the nameplates require similar circuits, I see no problem.
BUT- that's a big assumption. The two appliances are treated quite differently as to wire sizing and over-current protection; Just because they have the same plug is no guarantee. Nevertheless, in Harry Homowners' garage, where Harry is going to putz around solo, it ought to work out OK. Change that to a guy trying to run a business in his garage....and my answer will change.
I am fixin' to do exactly the same thing with my welder and a new pressure cleaner I just ordered. In a practical sense I know I could unplug one and plug in the other but I am going to install another receptacle.
I did the same thing at a big honkin' laboratory complex a few years ago. Each lab had a piece of equipment that the staff would roll to different places in the lab based on their particular research project. There were 3 possible locations, but each lab only had 1 machine...1 circuit, 3 receptacles. Worked great. No problems...Code or otherwise.
Please tell an innocent European why two appliances with the same voltage and amp draw would need different wire? I assume with some loads you could downsize some for cycling, but generally 30 amps are 30 amps, right? Trip characteristics are a different piece of cake of course.
I think mainly it's a design thing - we usually put our CEE receptacles on dedicated circuits, so they can be loaded to their full ampacity.