I want to add a 220V circuit. My electrical panel only has room for 1 more 1" circuit breaker. Do you think it would be ok if I bought a 1", 30/30 tandem breaker and made them common trip by adding a pin, screw, or tab to join them together?

No nick, you can't do that. The breaker which you describe is basically splitting just one side of the panel, one hot leg. The most you can get from that breaker is 120 volts.
You can use a breaker to free up one of the other full size breakers though, but it won't be a 30 amp, it will be a 15 or 20 to match two of the circuits you already have. What do you need a 30 amp breaker for?

Is this the same project as this? https://www.askmehelpdesk.com/electrical-lighting/addition-220-outlet-welder-437308.html

I need a 30 amp breaker for a MIG welder. If the 30 amp tandem breaker has 2 screws for hot wires, I don't understand why I can't use 10-2 wire with ground and put the black wire under one screw of the tandem breaker and the white wire under the other screw of the tandem breaker and thus creating a 220V circuit. All I would have to do is connect the 2 switches to make a common trip for safety. If the tandem breaker has the capacity for 2 separate 110V lines, if I connect both the black and white wire from the same 10-2 wire to each leg of the tandem breaker then I have created a 220 V line. In theory this should work because I am getting 110V from the black wire and 110V from the white wire and connecting them to a 220V receptacle. Please advise further if able. Thanks

Yes it is the same project but I don't think I explained it properly.


Got it, Now I understand why you need 2 spots. Sorry for the ignorance, that's why I ask. Thanks for clarifying.

Nick. I can advise further but I can see that you simply do not understand how an electrical panel is laid out. I'll try to explain. When you look at your panel you have two columns of breakers. Every other breaker in the column is connected to a different leg of the panel. A tandem breaker is only connected to one leg. You MUST be connected to both legs to attain 220 (240) volts. That is why you need a true double breaker, not a tandem. What you propose would give you 2 120 volt circuits on the same phase. You would not get 240 volts from this setup. You theory is absolutely wrong.

Nick, you are very welcome. Glad I can help. But as I said you may be able to use a tandem breaker somewhere else in the panel to free up a space needed for the dbl. pole.

What you would get is 120V w/ respect to ground and 120 V w/ respect to ground, but when you would measure the voltage across the two terminals, you would get zero and you would scratch your hair out determining why,

You guys are very informative and add to my learning experience. Unfortunately I am out of space in my 200 Amp panel and have all tandem breakers in there. I will go with a 110V welder and take up my last spot. One other question on this matter. My central air cond. System is on a 50 amp 220v circuit and my garage heater is on a separate 50 amp 220V circuit. Since I will never use the 2 together do you think I could combine these 2 thus freeing up a double spot in my panel?

How about a small sub panel, It will take 2 spaces in existing panel, but will free up other spaces.

Nick, you can't do that either. Both devices need their own circuit protection. Stratmando's advice is probably the best anyone can give you. Invest in a small subpanel. Exactly how old is your panel, by the way? How many breakers do you have? It seems unusual to have a 200 amp panel full of tandem breakers. Was there a major addition that required this or just poor planning by the builder / electrician?

That is about the last resort. I am all filled up with tandem breakers on my 200A panel and I need more power. I have 100+ amps in the garage alone. So I guess a subpanel to the garage is the way to go. That will certainly free up tons of space in my main panel. Thank you all again for your help and for your generosity of knowledge.

My home is 10 years old and it was poor planning by the builder and myself. I have loads of 15 amp tandem breakers through out my panel. I have 5 bedrooms all on separate 15 amp breakers. My A/C system takes up 100 amps and 6 spaces. I have a sump and a basement bathroom with an up pump and according to NJ code they both must be on separate 20 amp breakers, I have a 50 amp 220V garage heater, 2, 20 amp outlets in my garage and a 220, 50 V outlet for a compressor. BTW the house is 4000 sq.ft. and I wonder if I can bring in more power, perhaps 250Amps. K.Hovnanian was the builder so that says it all. Thanks again. I will run a 100A sub to the garage and free up 6-8 spaces in my panel. I should have done this a long time ago and would have saved a small fortune with all the 6 and 8 gauge wire that I bought. I am a car hobbyist and use equipment that takes up lots of power. It really was poor planning on my part when I come to think of it.

If you upgrade your panel you certainly can bring in a higher amperage service, like 400 amps. Changing the panel may be a step in the right direction, but it will be expensive. But in a 10 year old house I suspect that any electrical improvements you do will be an investment for you. How many spaces do you have in your panel? (spaces, not breakers) And is it a 200 amp service you have now?

I have 20 spaces and 200 amp service. I would really like another 50-100 amps. I remember when I had the house built I paid an upgrade charge to get 200 amps over the 150 that was standard. 200 was the most available at the time. I don't know if that has changed. Can the electric co. run another line in for another 200 amp panel? That would be great. All I need done is to pay for the line and the panel installation and I could take over from there. My wife won't be too happy though because my electric bill is just north of $500 month now, 75% from my garage and that is with gas heat in the house! The car restoration keeps me sane though. Thanks again for all your help.

For several years I have been using a vent free gas heater with ods in the garage. I think it cost less than $300.To heat with gas is about 1/3 the cost of electric heat. For much less than the cost of an electrical service upgrade a plumber could run a corrugated stainless steel gas line.

Also- If this is an undergound service the undergound may have to be replaced- a big mess and not cheap- and very likely out of your pocket. Here the underground belongs to the homeowner. This would also give room for you mig welder and a wire in the garage for its use.

Or use the 50 amp heater wire for a sub panel once the gas heat is in.

That certainly sounds like a good option especially since the main gas line comes into the house from the outside garage wall and is about 5 ft from where I want the heater. That would free up 50 amps and basically solve my electric issue. I have a 4 car garage about 40ftx45ft so what size gas heater would I need? My electric heater is 60,000btu. And if I run it on weekends only at about 25-30 degrees outside to heat the space to 60 degrees it will cost me $400 month. Insanely expensive since the car restoration is only a hobby and not how I make a living. I was misled as to the cost when I bought this heater and was told that gas is only 75-80% efficient and electric is much more efficient. I agree it is more efficient but at a steep price. May try and sell the electric heater and look into gas. A vented unit wouldn't really be a problem either since I can send it out and up right from the outside wall of the garage. Thanks for all the great ideas, I appreciate your time and wisdom.

I can't say how much heat you need, too many variables. The unit I use is 30K BTU and I see Northern Tool has it for $170. If you need 60K install two, the price is right.
Natural gas is purchased by the "therm", which is 100,000 btus. At the moment I think a therm delivered costs about $2.00 (I could be wrong, ask your utility). Since electric heat puts out 3.4 btus per watt 100,000 btus is roughly 30kw. At 25 cents per kilowatt that's roughly $7.50 per therm. A hugh price difference. Once again check these numbers with your utility. If you use vented heaters figure that about 25% of your money will go up the flue pipe. The unvented heaters are safe. Try to find one report of injury from them. Another thing I like is they have no electrical connection. It the power is out you still have heat.

p.s. If the dollar figues are wrong let me know.

Than you very much. Gas seems the way to go.