Table Saw Dsiconnect

[George Bregar]

I've posted this before but searches have come up blank.

I've run the power to my 3HP Unisaw under my slab and need to have a disconnect switch to cut power when making blade changes. My understanding is that the switch needs to be rated not only for the circuit (240V/20A) but also the HP of the motor.

Any cost effective suggestions electrical gurus?

[David Kumm]

George, how is the machine hooked up? A plug is a disconnect. A regular 240v switch is as well. Doesn't need to be a motor starter variety, just double pole. Dave

[Larry Browning]

I think one of those AC unit disconnects will work fine.
I am working out the details for hooking one up to mine.
Here is a link to a recent thread about the subject
http://www.sawmillcreek.org/showthread.php?180994-Scary-Stuff-Saw-Starts-Due-to-Vibration!

[George Bregar]

George, how is the machine hooked up? A plug is a disconnect. A regular 240v switch is as well. Doesn't need to be a motor starter variety, just double pole. Dave

No plug/receptacle which is why I need a switch. If this is true, then easy. I can mount a box on the back of the saw.

[George Bregar]

So just this?

http://www.homedepot.com/h_d1/N-5yc1...&storeId=10051

[Matt Meiser]

The one I linked to in the thread Larry linked to is a better choice in my opinion than an AC disconnect. An AC disconnect requires you to open the cover and pull out a piece. The lever style is easy and very visual as to whether you remembered to switch it or not. And they are only around $20 at Lowes.

I also found this one at Lowes for $15.

If your saw has protection for the motor built in, and it would unless you or a previou owner have changed the electrical and did away with it, and you've got a proper breaker on the circuit, the disconnect doesn't really need to protect anything so you can just put the biggest fuses that will fit in it. I've got 30A fuses in mine and its a 20A circuit. If I ever overload the motor, the starter will trip to protect the motor and if I ever overload the circuit the breaker back in the panel will trip. Or maybe if there's ever a short the fuses might blow before the breaker depending on which acts quicker.

[George Bregar]

The one I linked to in the thread Larry linked to is a better choice in my opinion than an AC disconnect. An AC disconnect requires you to open the cover and pull out a piece. The lever style is easy and very visual as to whether you remembered to switch it or not. And they are only around $20 at Lowes.

I also found this one at Lowes for $15.

If your saw has protection for the motor built in, and it would unless you or a previou owner have changed the electrical and did away with it, and you've got a proper breaker on the circuit, the disconnect doesn't really need to protect anything so you can just put the biggest fuses that will fit in it. I've got 30A fuses in mine and its a 20A circuit. If I ever overload the motor, the starter will trip to protect the motor and if I ever overload the circuit the breaker back in the panel will trip. Or maybe if there's ever a short the fuses might blow before the breaker depending on which acts quicker.

Matt, I followed the link and I was actually looking at the same unit before I posted this. But why not just a simple switch like this? http://www.homedepot.com/h_d1/N-5yc1...&storeId=10051

[Buck Williams]

George,

A simple HP rated toggle switch is called a manual controller. Pass and Seymour, Hubbell, Leviton all make them. Do a search for a P&S PS20AC2HP to see an example.

[Larry Browning]

I think you want a disconnect, not a switch. A switch can fail, while a disconnect is designed to do as it's name describes, disconnect the power completely. A switch does not do that. Plus, the switch can be accidentally turned on. Just my thoughts, I am no expert.

[George Bregar]

George,

A simple HP rated toggle switch is called a manual controller. Pass and Seymour, Hubbell, Leviton all make them. Do a search for a P&S PS20AC2HP to see an example.

Just to be clear, I want to simply disconnect power when changing the blade. I will use the magnetic switch on the unisaw for operation. The item you listed is rated for 2HP I believe also, right?

[Matt Meiser]

I guess my thought is for an extra $10-15 you can do it the proper way. Personally I wouldn't trust a switch--I've had light switches fail ON at home. With the disconnect there's a very positive disconnect. I realize these are a little better built but is it worth the risk?

I think I've got a couple older used disconnects hanging around. If you want one I send it for the cost of shipping. I'd guess any would fit in a large flat rate box and some might fit in a medium flat rate box.

[Van Huskey]

I have always used a A/C disconnect, I prefer the one with a breaker type switch inside but it NOT a breaker. Because they are code required they are available everywhere and inexpensive. The "breaker" type I use does require you to open the box but you don't have to pull anything, just flip the switch. And unlike the lever outside or the standard switch you or anything else can't just bump into it and turn the power on, or off. The other positive is it comes with the box and it is assembled all you need is the romex connector (the thing that clamps the wire going into the box, who's name escapes me).

[George Bregar]

I guess my thought is for an extra $10-15 you can do it the proper way. Personally I wouldn't trust a switch--I've had light switches fail ON at home. With the disconnect there's a very positive disconnect. I realize these are a little better built but is it worth the risk?

I think I've got a couple older used disconnects hanging around. If you want one I send it for the cost of shipping. I'd guess any would fit in a large flat rate box and some might fit in a medium flat rate box.

Well, not only would the switch have to fail but also the mag switch on the saw. But I think for $20 I'll go with that Lowes disconnect. Thanks, and thanks for the offer.

[David Kumm]

George, you have lots of choices. I agree that a full disconnect is the best deal although i hate the cheap $15 variety. A disconnect and a switch are the same thing although the disconnect has a more positive throw. Bump proof covers are what you want on a switch on a machine whatever you choose. You are looking for a second layer of protection. Testing the main starter after the disconnect is the only real way to insure the circuit is broken unless you open the disconnect box to verify. Dave

[Matt Meiser]

The "breaker" type I use does require you to open the box but you don't have to pull anything, just flip the switch.

I don't think that type is readily available around here, at least at places that are open hours that working folks can get to them. Probably a regional thing.