shop electricial question

I'm not sure if I should use 30 Amp or 20 Amp breakers. Any drawback to the 30Amps?

Also, what is the difference between single and double pole breakers? Many thanks. James

I'm alway refering to to this book just for the line drop tables alone.

'Wiring Simplified' by H.P.Richter and W.C.Schwan ISBN 0-9603294-7-1

This book is based on the National Electrical Code, it 5.5" x 8.5" 225 pages or so and lists for $9.95 + $3.00 S&H or $12.95 1-800-841-0383

• Wiring Simplified

What size of service to put into your shop would depend on the size of the loads you intend running and, to a lesser extent, their frequency of use.

A basic single-pole 120V 15A circuit, ground-fault protected, is the basic code requirement for a basic garage, and would be adequate for running basic hand tools and low-power drill presses.

A "working" garage would probably do best with its own sub-panel. A 30A 240V panel can offer up to four 120V 15A circuits, or two of these along with a 240V 15A two-pole circuit suitable for a small-size 240V MIG welder. There are a number of light-duty MIG welders about (Century 105, for example) that run on 120V for "convenience" but these really do require a minimum of 10awg wire (larger if the run is more than about 20 m) to handle the current thermal load and limit the voltage drop) and would of course require a 25A or 30A breaker; this would be single-pole in the case of a 120V welder.

Note that "double-pole" breakers are there to service 240 loads, and/or to assure balanced use of the incoming service. 120V loads use one side of the utility transformer only, and the main panel distributes such loads more or less evenly on both sides of the transformer center tap. 240V loads use the full secondary winding. Heavy loads on one side of a transformer only cause hot spots and power quality problems and shorten transformer life.

Good luck with it.

E G Kenward
senior member, IEEE
senior instructor,
Power and Industrial Control
School of Electrical & Computer Engineering
BC Institute of Technology, Burnaby, CANADA

• Some styles of plugs

Many thanks. James

Your question it one that brings out all kinds of replies: It sounds like you don't know a whole lot about electricity, and just want to put some stuff in to make it work. So please take the rest of this in the firendly spirit it is offered, from another person who would like to do some wiring but doesn't know allt hat much about it:

Please be careful. It is pretty easy to hook up wiring that makes a light go on & off, or makes a drill work when you plug it in. But it's _real_ hard to make everything meet code, be safe, and put all 4 wires to the proper connections all the way through if you don't understand the concepts. The drill will operate even if you mix up the hot & neutral wires - the drill will operate if you confuse the nuetral & ground wires. It will operate if you don't connect the ground wire. But, all of that makes it really unsafe for you & others. A shop tends to have sawdust, tools, metal, paint fumes, liquids, and so forth pile up.. Person works when it's cold or dark or after hours when you are tired..... And that's when the electrical 'mistake' will show up - when you are standing in a puddle of snow melt and grab the improperly grounded drill. If you connect the ground to the wrong place, you could mess up the ground for your whole house, not just the 2 outlets you put in...

There are lots of local codes, I'll bet you are covered by some. They may or may not make sense - but are the law. But you should at least understand the national electrical code that applies to what you are doing, and follow that. It really, truely, is there for your safety. The national code mostly does 2 things - keeps the wires from melting & burning down your house, and keeps you & your family from being a conductor of any electricity _if something goes wrong_. If you don't know what you are doing, you really won't know if you got it right until _something goes wrong_. Could be years from now.....

So, do it right, do it to the national code. Understand that much. By law, you need to follow local codes.

If the house burns down & the wiring was wrong, your insurance company might not pay if you didn't follow all codes.

If a family member gets hurt, how will you feel?

To answer your questions a bit, from someone who doesn't really know too much: I think all consumer grade wall outlets at 110v are rated for 15 amp or 20 amp. I don't think a 30 amp breaker would be proper, as the wall outlet could overheat & fail at 30 amps, and the breaker would not be protecting you. If you have a 220 load - welder, air compressor, etc. - then this does not apply.

I think the single/ double throw was covered already, 110/220 power.

For a shop, it is wise to use a size thicker wire to cut down on line-resistance loss. Really helps your motors last. But you need to start in the main power box & make sure all the wire is at least that size - don't tap into a #12 wire with a #10 addition.....

--->Paul

Actually I've put in wiring for stoves, attic fans, shop lights etc., but never outlets for bench tools. To me, building code is the minimum guideline I would follow. I wanted to see if more experienced hands would go beyond code requirements.

Later this week, I will put my first diagram on paper, put it away for a couple days then look at it again to see if I want to make any changes.

I spoke with a town inspector and he said that 20 Amps on each circuit would be fine along with 12 gauge wire. The also suggested GFI breakers in place of GFI outlets.

The tools I'm looking at running are rated at 15 amps, but I was concerned about the startup amperage hence the question about 30 amp breakers.

I also understand the reluctance to offer specifics on working with electricity, especially if you are a pro. A reader should always verify anything read from the internet, but nowadays people are so eager to sue that any advice givers have to be careful.

I do appreciate the help.Thanks
James

When I opened the load center door I found that all circuits were fused with 30a fuses and had been recently done that way.

I asked the owner who had changed the fuses to 30a and he said he did as his "brother" was a sparky and told him it would be the best thing to do. (ya, right, I was not born yesterday and didn't fall off a tomatoe, no a carrot, I mean a turnip truck)

Naturally I told him he needed to change them back and why he needed to do so. I noted this on my repair order ticket.

Next morning at 6am, I get a call from the home owner saying the air handler was on fire. "What are you calling me for, call the fire department and I'll be there"

Upon inspection, the fan motor had shorted out and since it was still fused with 30a fuses, hence the motor "total melt" down. It also melted about 18" of lead wire.

Now the day before I ran a motor voltage/amperage check, check the bearings, checked the fan belt and alignment, checked for loose electrical connections, etc, anotherwords I did my job.

It was just amazing how those motor bearings seized up when the unit did not call for either heating nor cooling over night as I had left the thermostat in the off postion, and I also pulled the 30a unit fuse, and noted the above on my repair order.

Can we say insurannce fraud!

The insurrance adjuster didn't buy it either.

I did however find it interesting on what did happen with a 115v circuit on a 30a fuse. The fuse was not blown as the wires had burnt off the motor terminals.

T_Bone

Enjoy the stories you guys always have on electrical items. Really adds a lot to the table. Thanks.

--->Paul