wireing problem

"Paul Gilbert" wrote: (clip) I assume that I need a double pole switch. Is that correct? ^^^^^^^^^^^^^^^^^^^^^ Correct. I have a printing press with two motors--each is controlled by a single throw, double pole switch. That suggests to me that these switches must be available as parts for various kinds of shop and industrial equipment. You could even use a knife switch of the type used in your meter box.

Check an electrical supply store. Or online, or maybe Radio Shack

DPST 250V returns plenty of options (google search)

Not the cheapest, but with good motor ratings well above what you want to run (safety factor)

Yes, they do. You're just not looking in the right place. Really.

That is correct.

actually, a single pole switch will work, but one side will stay live all the time so a double pole single throw switch is preferred - widely available - get a motor rated switch and do NOT go to radio shack for it.

for vac info, DL the article from my web page - it will give you some hints

"Bill Noble" wrote: (clip) do NOT go to radio shack for it. ^^^^^^^^^^^^^^^^^ There is a good chance that the clerk at Radio Shack won't know what it is.

One good reason, besides safety, not to use a single pole switch, even though it will turn the motor on and off, is that a double pole switch is much better at suppressing arcing. This is an issue on inductive loads like motors.

"Work" in the sense that it will stop the device from operating. But not safely...

.. for exactly that reason.

If by "preferred" you mean "required for safe operation" then I will not disagree with you.

note that the "one side live all the time" is pretty much unique to the USA, whose standard 220 is really based on a grounded center tap neutral - most other countries have a 220 that has a neutral leg and the hot leg is 220 above it, and the neutral is nominally at ground. So, in some other country - say the UK, a single pole switch on the hot lead would eliminate any "live" voltage past the switch.

^^^^^^^^^^^^^^^^^^^^ And your point is? Since this is the only place in the world where a two pole switch is needed, it must be only a technicality. This is the only place in the world where you can be electrocuted by a technicality.

aaah, no, my point was that in my experience that there are other countries in the world, and that sometimes residents of those other countries might read this news group, and that it is only common courtesy to suggest how a discussion that is unique to the peculiar way the USA does things might differ if it were applied to their situation. Because of our lawyer rich society, I have offered no opinion on the safety or legality of any switch configuration, I have merely offered specific information on the way that power is supplied world wide and how a motor might possibly be controlled by a device capable of interupting said power. Any application to actual electricity is at the risk of whomever elects to be in the presence of said electricity. Many countries have recommended configurations for such devices. Some countries even have laws and regulations governing the employment and application of such devices. It would be incumbent upon the user to establish saftey, legality, permitting, and to comply with all local, national, international, galactic, and intergalactic regulations that might possibly apply to their situation and to make said determination after proper consultaion with those fully authorized and empowered to supply said determination.

I hope that the above elucidates my position with respect to possible confgurations of power supplies and the means that one could in theory use to supply or interrupt them.

I'm sure that's news to thousands of electricians in Canada and Mexico.

True, but irrelevant. If the OP had been located in the UK, he would not have been looking for a DP switch to disconnect a 240V load. The fact that he *was* shows that he's located somewhere in North America.

As a UK resident, but with some electrical knowledge, given the option, I would much prefer to have double pole switching on any machine, or even on any circuit within the home.

The neutral is connected to earth at the substation, which may be some distance away. Current flowing down the neutral can raise the potential at the consumers premises by quite a few volts. Whilst not dangerous, the spark produced by accidentally earthing the neutral, on something you are working, on can give one a surprise. It can also take out any RCCD devices which may be in the circuit and cause some irritation, especially if it's the RCCD on the house incomer!