Electric disconnects

[Jeff Bartley]

And if someone can recommend a nice disconnect I'd love to see it! A search on the inter web turns up a lot of different options.

[Andrew Seemann]

If you have a main panel in the shop, the easiest is to use the breaker in the main panel feeding the subpanel. Next easiest would be to have a subpanel with a main breaker in it. After that, a safety switch with a big friendly handle or small breaker box that can fit big enough breaker. I probably wouldn't use something like an air conditioner disconnect, not sure if code would allow something like that. I think not, but I haven't looked at that section in ages.

Side note, make sure you keep your neutrals and grounds separated in the subpanel and run separate neutral and ground wires to it. That gets missed a lot. Don't put in the green bonding screw either, same thing, need to keep neutral and ground seperated.

Another tip, I leave a task lamp for my chop saw always on (LED bulb) and plugged into a circuit fed from the machine subpanel. That way I instantly know if I killed the power for the machines. I can even check from the house.

[Martin Wasner]

And if someone can recommend a nice disconnect I'd love to see it! A search on the inter web turns up a lot of different options.

Ask a local commercial electrician what they have laying around. Might be able to pick up a used 100 amp disconnect for next to nothing. It might be old, it might be dirty, but work just fine. I had a electrician friend of mine scavenging stuff that was just going to be tossed in a dumpster off of jobs for my shop build last year, I bet saved $5k easily.

A disconnect would be better than just tripping a breaker in my mind because you can lock out a disconnect with a padlock. There's times when that is very important. Maybe less so in a home shop, but if you're working on something you don't have to be concerned with somebody slamming the power on and you riding the lightning.

[Jim Becker]

Marin's idea has merit..."new" isn't required and a can of spray paint can easily and very quickly "clean things up".

[Jeff Bartley]

I would love to find a couple old disconnects! I was actually surprised the electrician spec'd breaker housings and breakers to use as a disconnect. I plan to ask about it on Monday.

[Bill Dufour]

If you have a machine that is hardwired in code requires a disconnect visible from the machine. In a home shop this usually means a cord and outlet. But for a dc or ac, mounted in a awkward place, a disconnect may be easier to access. Also it makes sense to have disconnect supplying a sub panel so you can work on the subpanel with out killing all power to the house and shop.
Bil lD.

[Terry Kelly]

I like the disconnect option better...breakers aren’t really designed to be switches....they will wear out prematurely...

[Joe Jensen]

Lots of options on ebay. I searched for (electrical disconnect). Looks like they are also called safety disconnects...joe

[Arthur Fleming]

Depending on the make of your panel/sub panel, they may actually make a switch rated breaker. I can remember installing them in a machine shop to turn lights off. Same short circuit, over load protection of a regular breaker, rated for use as a switch, also. Advantages are easily installed, and breaker cost (if available) your only expense. No wall space lost to a disconnect. I have seen many a shop use regular breakers as switches for years with no issues. For cost of a regular breaker, if you are competent of installing one (I’m not advising either way), could very well be more cost effective, even if you are replacing it every 5 years. If space and money are not major issues, I can’t see any negatives to adding a disconnect.

[Bill Dufour]

My uncle worked for Lockheed in San Jose. The was built during WW2. As the Vietnam war was ending work slowed and they would no longer be running 24 hours a day. Only took 30 years to find found out there were no light switches.
IEC breakers are rated for about 100,000 disconnects. NEMA about 10 times that many. So do not worry about switching off breakers as a disconnect if they are not under load.
Zinsco breakers seem to last for one over current event between failures.
Bil lD.

[Kevin Beitz]

The last factory I worked in had switch rated breakers.

[Osvaldo Cristo]

If I had intention to cut power from a typical shop, with a reasonable load connected, I would prefer to use a contactor, an electrical relay, using NO (normally open) contact.

High amperage switchers cost a lot of money if from a respected manufacturer. Relays can be cheaper and safer as you command it with a lower voltage/amperage auxiliary circuit.

I do not use them in my small workshop. I have the discipline to unplug any not used electrical machine. My shop has concrete walls, ceiling and floor. Connected to our garages with a locked steel door. It is enough for me.

Good luck in your project.

All the best.

[Jeff Bartley]

For a follow up on this: my electrician recommended breaker housing panels for disconnects, he said those breakers are made to be switched on and off.

I now have two disconnects off the main panel; one feeds a sub for single phase machines, the other feeds a phase converter and three phase panel. But the most interesting thing the electrician recommended was a wire trough over the two sub panels.

By placing the trough over the two subs I can swap single and three phase circuits easily provided I run 4 wires to each outlet. I really want the flexibility to move machines around!

Thanks for the discussion folks!

[ray grundhoefer]

many years ago using a breaker as a disconnect was not a good idea. However I believe now pretty much all breakers are SWD which means switching duty

[Rod Sheridan]

Every heavy industrial shop I've ever seen ONLY used the breakers to turn on/off all the shop lighting in the place. On in the morning, off at night. Of course, this is the single phase 277v on a 480/277v system so they are quality breakers bolted in place.

Greg, they probably had breakers rated for switching duty in the lighting circuits...........Rod.