Switches on 120v & 240V Outlets or not?

[Adrian Anguiano]

I think I have all my outlets positioned where I want them. Now I just have to decide if putting switches on the receptacles is worth it or not?

What do you all think?

[Justin Jump]

I wired my dust collection and air compressor to switches in the workshop, and the pieces are below in the garage. They are both 220, so I had to use single throw, double pole 220 switches. I think thats right!!

[Rod Sheridan]

Adrian, why would you want switched outlets?

The other consideration is that they will need to be horse power rated for the largest machine plugged into the circuit as they can be used as disconnect switches......Rod.

[Adrian Anguiano]

Adrian, why would you want switched outlets?

The other consideration is that they will need to be horse power rated for the largest machine plugged into the circuit as they can be used as disconnect switches......Rod.

My thought was instead of pulling out the cable anytime I'm messing with jointer or table saw blades, or changing a router bit, I could just flip a switch instead.

HP rated switch? Holy smokes, how do I find those ratings?

[Howard Acheson]

>>>> My thought was instead of pulling out the cable anytime I'm messing with jointer or table saw blades, or changing a router bit, I could just flip a switch instead.

I think it is safer to pull the plug. It's easier to see that it's disconnected than looking at a switch. I lay the power cord over the table or in a very visible location on the tool.

[Dan Friedrichs]

HP rated switch? Holy smokes, how do I find those ratings?

You need to buy switches that are explicitly rated for motor loads. Regular light switches from the box store will NOT work!

(If you're curious as to why: When you turn a motor off, it dislikes that - it "wants" current to continue to flow. So if you open a switch, that desire for continuing current flow causes an arc between the switch contacts. You'd see this arc anytime you quickly unplug a large motor. Standard light switches can't handle this repeated arcing, so you need to use special switches rated for this. In large industrial applications, turning motors off is a BIG problem and requires serious hardware to do)

[Ken Fitzgerald]

Dan.....same thing used to be true for DC lighting systems typically used in the scan room for MR scanners. The switches must have the appropriate DC rating....

I don't know if this changed with the use of self-shielding magnets....

[Dan Friedrichs]

That's really interesting, Ken - did they use DC lighting because AC induced some sort of noise on the MRI signal?

[Adrian Anguiano]

I think it is safer to pull the plug. It's easier to see that it's disconnected than looking at a switch. I lay the power cord over the table or in a very visible location on the tool.

I was going to use a switch with a glowing light.

But after everyone's comments I think I'll forget the switch. It will make the electrical easier to run.

[Ken Fitzgerald]

That's really interesting, Ken - did they use DC lighting because AC induced some sort of noise on the MRI signal?

They use DC lighting because if AC lighting was used, the reversing current in the presence of the very strong DC magnetic field would cause light bulb filaments to burn out very quickly . The field strengths we are talking about are 1.5-3.0 Tesla.

Interestingly enough, even with DC lighting...bad lamps with burned filaments can cause horrendous intermittant image artifacts. During a scan, the gradient magnetic fields fluctuating causes a mechanical vibration. This can cause the 2 pieces of the defective filament to vibrate and the vibration can cause momentary contact of the 2 pieces of defective filament. When they make contact, there is an instantaneous current flow in the form of an arc which creates an intermittant RF signal that gets received and factored into the image. Thus an artifact is created. First lesson in troubleshooting intermittant artifacts is replace or at least remove any bad light bulbs in the scan room.