Shop electric question

8ga Romex is good for 40a. THHN in conduit is good for 50a if you have 75 degree terminals in your sub-panel and breaker feeding it. (most do when you get over 30a) For a few more bucks you could go with 6 ga and have some extra capacity but I doubt you need it unless you expect to have more than one person running tools ... or a heater. If you are looking at electric heat, 80a may be more in line. Your sub-panel will probably have 100a busses and the breakers are pretty much the same price in these ranges so it is really just the price of the wire. Look back a few weeks in these electric threads here and there will be more than you want to know about 4 wire feeders and whether you need supplimental grounding rods. Supplimental grounding and disconnect issues only come up if this is a separate building.

Been there and done that. The 8/3 should be OK.I put a 100Amp box in the shop.

I have a 50 AMP breaker in my house. I designed the electrical circuits in my shop as not to overload either leg of the circuit.

The 220V incoming is actually 2 independent 110V "legs" or a single

220V line. As long as you do not overload either leg the breaker will not trip. I have 8 4ft fluroescent (sp?) fixtures - 4 on each circuit. I have an air conditioner 110V on the leg with the scroll saw and sander with 4 of the lights. The air compressor is on the other leg.

The TS and dust collector are wired to 220V so they are on both legs.

Sketch your shop and determine the demand for the 110V and the 220V. Arrange the source of the 110V legs to balance the usage.

Balancing the loads allows me to operate up to 100 amps of current at

110V on the 50 Amp circuit.

I have the following.....

3hp TS @220 Actually Craftsman 1.5 hp 2hp DC @220

Remainder 110V DEwalt planer Jet joiner

14" BS 1 hp Drill Press Osc Sander SCMS Scroll saw Midi lathe 5 gallon Air Compressor Bench grinder 10,000BTU Air Conditioner 8 4' light fixtures Delta air filtration unit

Without being under load I can run all the above tools in the shop. without tripping the breaker.

I have a single man shop so the loading is not a problem.

A little planning and you can really squeeze a lot out of your wiring without the overloads.

Good luck

It is almost _never_ a bad idea to 'over-size' the wire. Especially on a distribution run. The cost of materials is comparatively insignificant to the labor of running it. Bigger guage wiring results in less voltage drop in the wiring, regardless of load.

One of the "standard sizes" sub-panel is rated for 60A, 'generally adequate' for a garage shop.

Postulating the use of that size/rating of sub-panel, I'd run 6 ga wire, and use a 60A breaker in the main panel.

I just built a new shop next to my house and ran about 50 feet of cable to the building. I installed a 100 amp breaker in the main box in the house and ran 4 gauge lead in cable[3 separate wires ] to the shop where I installed a

With this set up, can you run any 220 lines? I'm going from my main panel in the basement (200 am service) into a sub-panel in the attached garage. I looked at the 20 circuit box at Lowes - But, I'd like to have 3 plugs that are 220 - jointer, table saw, and dust collection. Can I do it with a set up similar to yours, using 4/3 lead in to the sub?

The electrician wants $500 to do the sub panel, and $1,500 to the rest of the garage - seems high. I've added circuits to a main panel before - is this very much harder?

Thanks for any suggestions -

Nick

So far, there are two questions in this thread about adding subpanels. The phrasing of the questions leads me to make the following points:

1) At this point in time, you are in over your head. If you are willing to invest the time to learn about home wiring, the NEC, local codes, and whatnot, you can accomplish the task of adding a subpanel safely. All it takes is some time spent reading and learning, and you can save quite a bit of money. Most libraries have a copy of the NEC (1999 or 2002) and it's actually easy to read and understand.

2) GET A PERMIT! If you perform any substantial electrical modifications to your home, and said modifications cause a fire, your insurance company will absolutely look into whether or not the modifications were done with the blessings of the local building code people. If not, you can bet your sweet bippy the insurance company will NOT honor your claim. Most jurisdictions allow you to perform your own work as long as it is 'up to code'. This they determine by inspecting your work. In my county, an electrical permit costs less than $40.00. Cheap insurance.

3) I'm currently in the closing phase of adding two subpanels to my house - one in a newly built wall that separates my three-car garage into a two-car garage and a workshop. That panel is protected by a 60A breaker in the main panel. It is fed by three 6ga wires (two hots and a neutral) and one 10ga equipment ground. This panel contains two 220VAC circuits (table saw and dust collector), one 15A lighting circuit, and one 20A outlet circuit. The second subpanel (located on the outside back wall of the house) is protected by a 100A breaker in the main panel; it's fed by three 2ga wires (two hots and a neutral) and one 8ga equipment ground. This subpanel currently contains one 50A circuit for a spa.

4) If you want to learn how to do this stuff right, I'd suggest you obtain a copy of the following:

a. Black & Decker's "The Complete Guide to Home Wiring" - ISBN

086573429.

b. Practical Electrical Wiring, by Hartwell and Richter - ISBN

0960329498.

Lastly, seek out a retired electrician that you can hire to 'look over your sholder'. I found a guy that charged me $25.00 per hour for his advice. I only used three hours of his time, but it was invaluable in answering questions that came up.

If you have any specific questions, feel free to ask away.

rob

Rob Jones, Developer Lightspeed Systems

From one who does all his own electrical work ... your advice is excellent.