I have a 3.5 car garage that is 24x34. I have a 8 space breaker box in the garage now, but I want to redo the electrical in the garage. The house breaker panel to the garage is a 50 amp double pole breaker and the same to the garage disconnect.
As the saying goes, anything worth doing, is worth doing RIGHT. While you MIGHT be able to just barely squeak by on that 50A feeder, for awhile, you really ought to upgrade it while you're doing everything else, and be done with it.
The following is what I'd like to do, let me know if you would change anything:
1st Breaker) 15 amp single pole with 14 gauge wire. For nine T8 shop lights and outside garage door lights. The T8 shop lights would be 64 watts each. That same line would have a junction box to supply three outside LED lights at 10 watts each. Total of 606 Watts. GFCI to start the run.
Stop right there.
Plug-in "shop lights" make for LOUSY general illumination in a typical residential garage, for several reasons. First, as mentioned by "87jeepwrangler", fluorescent lights and GFCIs often do NOT "play nicely" with each other. Your permanently-installed lighting should be just that: Permanently installed and hard-wired.
Second, unless your ceiling is EXCEPTIONALLY high, the reflectors on typical "shop lights" are counterproductive. They serve to concentrate the tubes' output in a more-or-less straight-downward direction, while limiting distribution to the sides. That means you need still more fixtures, each spaced closer to the next one, than would otherwise be necessary, in order to maintain even coverage.
Most common/cheap "shop lights" are NOT rated for direct surface contact. Hence, they would need to be hung (typically via chains) at some distance lower than the ceiling in order to maintain proper heat dissipation. That further exacerbates the light-distribution problem described above.
I also agree with "87jeepwrangler" that 18 F32T8 tubes is marginal at best for over 800 ft.^ of floor space (arguably, it's simply not enough). Nor am I thrilled with your proposed layout, which squanders much of what little light you have by placing fixtures directly over the vehicle parking spaces. Just how often do you need to brightly illuminate the roofs of the cars?
You will also want some dedicated task lighting over at least your workbenches.
Finally, you really want to dedicate TWO 15A circuits/breakers for your lighting, for reasons which have little or nothing to do with load capacity.
2nd Breaker) 30 amp double pole with 10 gauge wire. For one 5000 watt electric heater.
Is this unit purchased/installed yet? If not, I might suggest that you hold off. 5,000 watts is not much in terms of electric-resistance heat, especially in a Northern climate like Wisconsen.
3rd Breaker) 20 amp single pole with what size gauge?. For eight wall receptacles. Question, what size wire would I use for this? I have a few power tools, but nothing serious. GFCI to start run.
AWG 12 wire is normally protected by a 20A breaker.
However, again I would strongly suggest at least TWO such circuits for your general-purpose 120V outlets. Put a double-gang box every 6-8 feet around the entire perimeter of the space (except where overhead doors obviate this, of course). Feed TWO runs of 12-2 NM-B to those boxes, connecting one duplex to each circuit. Yes, the first box in the "daisy-chain" needs to use GFCI-type outlets (and the "downstream" ones are in turn fed off the GFCI's "Load" terminals).
4th Breaker) 15 amp single pole with 14 gauge wire? For two 1/2 horse 540 watt garage door openers. Total of 1080 watts. GFCI breaker?
If the GDOs use plug-in cords, then by code the outlets serving them need to be GFCI-protected, even if they're mounted in the middle of the ceiling. But this is similarly problematic to running large-ish fluorescent loads off GFCI circuits: You can expect nuisance trips. It would be better to convert the GDOs to a hard-wired installation, and dispense with the GFCIs entirely. After all, those devices are NOT going anywhere; so why the need for a "portable" power connection?
5th Breaker) is the 50 amp double main to the garage disconnect.
Witch would leave me with one spot left.
Not even that much, after you account for the suggestions above, and the various equipment you ARE likely to want/get in the future. Like I said, NOW is the time to do this right. Bite the bullet and put in a bigger panel, and feed it generously.
I was thinking about putting in a switch for the heater too.
You'll bankrupt yourself trying to heat that much space with just electric-resistance heat, especially if you're NOT getting a break on the rate from your PoCo due to the house itself being similarly heated. (Such rate breaks generally require a separate meter for the heating system, and ONLY the heating system.)
If you have natural gas available, that is the way to go as far as the initial heat source is concerned. How best to DISTRIBUTE that heat is another matter, and depends on things which are (at least at this point) outside the scope of this thread.
Maybe a 220 line would be a good idea for a compressor down the road.
Count on it. And other "stuff".
