I want to install a sub panel in my garage mainly for Christmas decorations. I have an unused 220 out let in the garage, that I was thinking I could use to feed the sub panel. However it was installed by the previous owner, and I am not sure what circuit it goes to in the main panel. My assumption is that it goes to a set of ganged 50AMP breakers that was originally for a spa tub that is no longer installed. Even if it doesn't I would like to use these breakers so I can have 100AMPS at my sub panel (main panel is 200AMP).

The sub panel will be about 50 feet from the main panel. The existing 220 outlet is about in the middle of the main panel and where I want the sub panel. Can I put in a junction box in place of the outlet and continue on to the new sub panel, or do I have to run a new line, also what exact size and type of line will I need?

Thanks

If it is #6 wire, you could put 60 Amp sub panel. #4 good for 100 Amps. 60 Amps is usually good? For Christmas lights. If you need 100 Amps, probably better to run complete new line, without junctions if possible. Leave Existing Alone. Other uses for that

Make sure the existing wiring is 4 wire.