[CarWiz]

That looks like a start for a dandy oven. You could probably get by with a single 3kw heater. You'll need to add some insulation and possibly an exterior wall.

Your electrical box appears to be supplied with 240v but it's split into two segments or legs of 120v. Both breakers look to be 120v. You can't just plug in a larger breaker until you check the use of the other two lines on the right. The supply line to box looks like 10ga. wire and you've got more than half of it's capability used up on those two circuits. On top of that, the two 120v circuits are running off one leg. They should be balanced across the feed.


To get 240v, you need both legs available for a breaker and that box doesn't look like it will take a 240v breaker unless you pull the two that are in there now. That will kill the two circuits on the right. It may take a 240v breaker in the middle and two singe 120v breakers on either side of that though. I can't see the runners in the box. Even so, you don't want to overload the supply line.

You need to go back to the box that supplies that box and see how it's being fed. A 3kw heater will draw 12.5A but you need to allow some margin. I'd say a minimum of a 20A breaker. The other two circuits are 15A each so you're really over the maximum for that feed line at 50A total. That would be living on the edge if the other two circuits are being used.