30/50 amp split breaker

I got a 100 amp service panel at my house with 30 amp and 50 amp circuits in it. It is full and I need to add a 50 amp circuit for my welder. I talked to a couple of electrians and they said to add a sub panel. That sounds right to me but then one said the they could replace the 30 amp double pole breaker with a 30/50 amp quad-pole split breaker and I wouldn't need a sub-panel. It would be alot cheaper that way but don't really know if that is safe. Any thoughts?
craig
Beer 4U2

 

It depends on the make and model of the panel; let us know what you have and we can tell you if the quad breaker will work and be safe. The panel number will usually include a four digit code like ___3040__ which means 30 spaces and 40 circuits and implies up to 10 tandem breakers are allowed. You would also need a quad breaker which has CIT (common internal trip) on both "sides" which could be a hard part to find in those amperages.

If you panel allows tandems, another option may be to move some of your other general-purpose circuits to single-pole tandem breakers such as 20/20 or 15/15 to make room for a full-sized double-pole 50A breaker, depending on availability and price of a 30/50 common internal trip breaker.