I have built up an old motor into a fair 10 inch disc sander. The
motor was wired for 240 V, I could not figure out how to re-wire it.
After a quick trip to the hardware store, I came home with an
expensive (13 bucks) wall switch. A 4 way. The kid assured me it
would work to switch on a 240 volt motor.
I think maybe shouldn't have listened.
Will this switch work? I tried it, but it was always "on", either way
I flipped it, the motor ran. I followed the labeling on the switch,
as to "load" and "source".
I would like to be able to turn both legs off at the same time. I
understand that the motor would stop if I cut current to either leg.
(after several Google searches.)
If I have the wrong switch, could someone suggest a better one?
Sure, go to your local electrical distributor, or even RadioShack and
get a plain old DPST toggle switch. Make certain that the contacts
are rated for use at 240 and are of a proper HP (or even amperage)
Should cost you about $4.00.
3 and 4 pole switches are only set up to switch one hot lead.
Take it back to the store and tell them you want a double pole switch. It looks
the same but it is wired differently internally. The one you have simply swaps
the inputs. That is used in "3 way switch" traveller legs. A double pole switch
opens both legs
This is how a four-way switch works:
(position 1) (position 2)
o----------o o-----+ +--o
o----------o o--+ +-----o
So no matter what position the switch is in, it's still supplying current on
Yes, but it's *much* safer to cut current to both legs at once. *Don't*
interrupt only one leg. It isn't safe. Do it right.
Take the 4-way switch back, and tell them you need a double-pole switch. Any
hardware store that sells 4-way switches probably sells double-pole switches
too. Although it looks about the same on the outside, it ain't the same on the
inside. Here's how a double-pole switch works:
(ON position) (OFF position)
o-----------o o-----\ o
o-----------o o-----\ o
Doug Miller (alphageek at milmac dot com)
How come we choose from just two people to run for president and 50 for Miss America?
Not so stupid.
Get a switch that is rated for motor control. Don't fool around with cheap
stuff that will cause you more harm than good. Unless you shop at HF, then
Here is the correct switch. I just installed a few and they work great.
Some motors are 240 *only*. thus it may not be "re-wireable".
You *do* have the wrong switch.
The kid lied. Perhaps not intentionally. (The switch may be 'rated' for
240V, but it is -not- usable as a simple "On/Off" switch for two hot leads.
A '4 way' switch is used in multiple-switch (*more* than 2 switches) lighting
circuits. It has 4 contacts, call them A, B, C, and D. A and B are the
'source' leads, C and D are the 'load'. When the switch is in one
position, A is connected to C, and B is connected to D. In the _other_
position, A is connected to D, and B is connected to C. This works to
turn on/off lights *only* when it is wired with a "3 way" switch on _each
side of the 4-way one. one of those 3-way switches connects the hot wire
to _either_ A or B, and the other 3-way switch connects _either_ C or D
to the load. Thus _only_ A or B is 'hot' at any given time, and -only-
C *or* D is connected to the 'load' at any given time. So, in one position,
the light is on, and in the other it is off.
What you require is a "Double Pole Single Throw" (also known as "DPST", for
short) switch -- which is, in essence, two 'regular' on-off switches "in
parallel". It _also_ has 4 contacts, A, B, C, and D. But here is the
difference: in one position, A is connected to C, and B is connected to D,
while in the other position *nothing* is connected.
Take the one you have back, and demand a full refund. The employee mis-
represented the product.
I'd think you should be able to get a DPST at that store. They tend to
be somewhat more common than the 4-way ones. *HOWEVER* the price seems
high for a regular 'toggle' type wall switch. About typical for a "Decora'
style one though. I bought a regular style 4-way wall switch at one of the
BORG a few months ago. I think it was $4.99. DPST should be in the same
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