I built a 30x30 workshop and have a few electrical questions.What amp size service panel will I need?Will have 8 120v receptacles and do they all need separate 20 amp breakers with #12 wire?Will have 2 240v receptacles, air compressor and a stick welder, what size wire and circuit breakers for those two components?Will have 8 fluorescent lights with 54w bulbs, How many lights can be on the same 15amp circuit with #14 wire?
1. Look at the nameplates on that compressor and welder. Each will have 'Minimum circuit required', 'minimum wire required' information. The receptacle required will have a NEMA number listed, (6-30R eg.) The 30 is the ampere rating. (I strongly suspect that that's a transformer type welder and the welding range amps are not an indication of the breaker required.). 2. Add up the total lamp wattage of each fluorescent fixture to get watts per fixture. Add up the fixtures on each switch. You can probably put 900 sq. ft of fluorescent lighting on one circuit 'load-wise', but it's a good idea to have at least two circuits, so that if one goes bad you have some light to chase the problem by. 3. Workshop receptacles need to be GFCI protected. For a shop that size, unless you've carefully worked out the plan, I'd recommend installing more than 8 receptacle boxes, and use double gang, (two duplex rec), boxes with one duplex on each circuit and two boxes per 3 wire run. The larger boxes and extra duplexes are cheap and the convenience is worth it. Do be aware you need a driven ground for that service panel.
I would put the fluorescent lamps on two separate circuits. The reason is that you will still have lighting if you have to do maintenance on one of the fixtures. I would also put the 8 120vac outlets on two separate circuits. Your air compressor should be on a 40 amp circuit. Your welder is on a 100 amp circuit from a sub-panel. It's highly unlikely you'll use the compressor at the same time you would be using the air compressor. Both are intermittent duty. From your limited info, I would go for a 150 amp service.
Need more detail for a good answer. What is the amp rating of the welder and air compressor? Also, will any of the 120 volt outlets be dedicated to single pieces of machinery, particularly high ampacity tools? if you are going to have any of them feed pieces of equipment (like a lathe or drill press for example) that outlet should be on it's own circuit. if these are just outlets for portable tools like drill motors or a skilsaw, you could have all of them on one circuit, technically. But I would split it between at least two circuits so if you overload one the other stays hot. Same with the lighting, you could put 8 two lamp fluorescents (I presume you are planning to use 2-lamp 8' fixtures with F54T8 lamps) on a single 20 amp circuit but I would suggest two 15 amp instead, That way you can turn half or all of them on for efficiency. Can't give you service size without knowing the ratings on your equipment. A 60 amp subpanel is usually more than enough for a shop that size. You also didn't mention other potential loads like overhead door motor, electric water heat for shop sink, echaust fans or electrically powered heating units. Have you accounted for everything?
In Canada and the USA 15 amp circuits are the norm wired with # 14 cable unless the runs are very long. Up to 12 outlets can be place on one circuit but for a workshop, I would sugest no more the 4 or 5 per circuit. If you require a 20 amp circuit, it should be a dedicated circuit with the proper 20 amp receptacle. A separate 15 amp circuit for your lighting is smart in case you trip a breaker with one or more of your shop tools; you will still have lighting. The welder will require a dedicated 240 volt, 60 amp circuit Your air compressor will also require a dedicated 240 volt circuit sized accordingly to the power demand of the compressor motor. Just from what you have listed, I would suggest at least an 100 amp 240/120 volt load centre. This will give you extra room for fans, heating, etc.
You'll want to use a 125amp breaker panel, with a main breaker (safety), How far from the house is the shop? Or is the primary structure on the property? I'd get at least a 20 space panel, you may need to add something in the future. What will you be doing about heat, if it's gonna be a wood shop you'll need some dust collection (Trust Me There!) For the air comp you'll want to run 10/3 MN to a 10-30R 250v 30a receptacle from a 2 pole 30amp breaker For the welder you'll want 8/3 MN to a 10-50R 250v 50a receptacle from a 2 pole 50 amp breaker The 120v outlets in a shop I would run only 2 on a #12/2 MN from a 1 pole 20amp breaker, if I remember correctly you're allowed up to five on a circuit but IT IS A SHOP you don't want to have your equipment starving for power. You'll have another 3 circuits with only two outlets set up exactly the same. I'm not sure how many lights are allowed to be on one circuit, but I would run 2 circuits with 14/2MN have four lights on each circuit, so you'll need two switches so what, they'd each be on their own 1 pole 15amp breaker
