Now many home improvements can be a DYI project, but wiring a 240V-50A line is NOT one of those things.
The HELL it's not. I did the wiring on my home improvement - including upgrading the drop to 200A service - and (unlike my uncle) I'm not a licensed electrician or electrical contractor.
Here's the drill:
- Read up on the subject. Use several sources. One should be the electrical code itself.
- Do some initial planning, then talk to your local code inspectors BEFORE you TAKE OUT THE building permit and start the project, and adjust the plans accordingly.
- Do it WITH a building permit and inspections. (The fee for the permit pays for the inspectors!)
- Try to get it right, or as right as possible, the first time. Inspectors don't like to find a bunch of problems to be repaired. (It makes them worry that there are more they might have missed.) Fix whatever they spot, don't argue about it. Answer all their questions and be helpful.
- DON'T use aluminum wire, EVER! Use copper and pay the extra price. (Getting aluminum wiring right is hard, requires special tools, and you can't really tell if you goofed. If you get it wrong, it wil burn you down in a year or a decade.)
- When the code offers you options, go for the better approach, rather than the corner-cutting way.
- Look for the UL label (or your country's equivalent) - on EVERYTHING you use.
Things to remember about the electrical code:
- The national code is a model. Some cities adopt it verbatim, some with changes, a few roll their own. But the REAL code is the way your inspector interprets it.
- Be nice and helpful with the inspector. Don't argue. (Feel free to ask what you misunderstood about the code, what you're doing wrong, what the purpose of some fine point is. But don't take TOO much of his time.) He has the authority to shut down your project. Respect that.
- If you DON'T do it to code, and with a permit and inspections in locations that require it (almost all of 'em), and your house then burns down (even if your work didn't start the fire), your fire insurance can pay you nothing (and keep all the premiums you paid over the years, too.)