I am in the process of wiring my workshop and wanted to be able to have a
single cutoff switch for the circuit so that I can cut the power to the
circuit when I exit the workshop (for safety reasons).
Looking at the switches at Lowes and Home Depot, while they handle the 220v,
but it appears that I would need two switches for each circuit. One for
the black side, one for the red side.
Is there a wall switch that I can install that will cut the entire 220v
circuit off with one switch? Or do I need to do similar to what a ciruit
breaker does by combining two breakers (switches) together to shut off the
I am installing several circuits, so I want to limit the number of switches
required to shut off the power in the workshop.
Any advice is greatly appreciated.
Yes. Look for/aks for double-pole switch. They're less
common so not usually stocked in the high volume places. It
will open both hots simultaneously with one switch. IFF
you're in the country I think you're in. 220 not
necessarily = 220 the world over.
You need a 2-pole switch. I think DPDT switches are used for 4-way
light switches, but that might not be heavy enough duty for electric
motors. Look for an air conditioner disconnect (available fused or
unfused.) They are cheap and heavy duty.
I would use a small main-lug breaker panel. A 70A panel usually has 2
or 4 spaces, and 125A panels with 6 spaces are common (and cheap, but
not as cheap as an A/C disconnect.)
You're talking about two different things here, and you don't understand the
difference -- which could lead the OP to create a hazard if he buys a 4-way
switch, thinking it will do what he needs. It will NOT.
A 4-way switch is a special type of DPDT switch, which does NOT disconnect
power -- it only changes the route. Consider the four terminals as labelled A,
B, C, and D. With the switch in one position, A connects to B, and C connects
to D. With the switch in the other position, A connects to D, and C connects
to B -- manifestly NOT what the OP needs.
The OP needs a plain old DPDT switch, rated for 20A at 250V, which is easily
found at Lowe's or Home Depot.
A DPDT will work if he can't find a DPST. He'll leave one set of
terminals open. (BTW, I thought a 4-way light switch had all 6
terminals, not just 4.)
I would still use an A/C disconnect if there's just one 240V circuit to
switch. I know it can handle an inductive load.
The amperage you are dealing with will determine the switch you need. An air
conditioner disconnect comes to mind. Also if you are dealing with several
circuts you are creating a bigger problem.
The easiest solution may be to put in a second breaker panel that you run
just the 240 volt circuits out of. Run the lights and outlets out of the
"first" panel. Then you can shut off the main breaker in the second panel to
kill all the circuits at once.
Thanks for the advice.
I went back to Lowes this evening and here is what I found.
1. 20amp Double Pole Switch (Will handle up to 12 gauge wire)
2. 30amp Double Pole Switch (Will handle 10 gauge wire)
3. A/C Disconnect
While the 20amp DPST switch will probably meet the need, the quality of the
30amp DPST was much better and it does give me some flexibility in what I
It appeared to me that the A/C disconnect is a bit of overkill for my
particular situation, but I am curious as to ZXCVBOB's comment, "I would
still use an A/C disconnect if there's just one 240V circuit to switch. I
know it can handle an inductive load." What issues might I run into using a
30amp DPST switch that a A/C disconnect would be a better choice for?
I had originally planned to wire the shop with 12-3 for all the 220V
circuits, but now seeing the 30amp swithes and given that I might go to
something with a higher amp rating, I am now inclined to run 10-3 and use
the 30amp switches to disconnect.
There always is the option of just going to the breaker box to kill the
circuits, but I know that I will not think and skip going to the breaker box
when I get called away from the shop. If the switches are right above the
light switch, I will form a habit of killing all the power when I leave the
workshop. My father had his shop setup this way and it was easy to close
up, one swipe of the hand killed the outlets and lights.
BTW, as a part of this project, I have added another 200amp panel to run all
of these circuits from. Additionally of note, to give myself flexibility to
rearrange the shop in the future, I am running more circuits / outlets than
I need, but to me the expense now is minimal compared to re-wiring once the
space has been finished.
Thanks for everyone's input so far.
An inductive load will burn up the contacts on a switch fairly quickly
if you turn the switch on and off (especially off) under a load. I
can't see your 30A switch from here, and I don't know if you are
planning to only flip the switch when all the machinery is off or not.
Are you wiring a 30A 240V branch circuit? What outlets are are you
using, or is the machinery hardwired? (it's safer with a cord-and-plug
so you can yank the plug in an emergency to disconnect it.) Or do you
have a fused switch at each machine to provide overcurrent protection
and emergeny shutoff?
Unless you have individual fused switches at each machine, I think a
small load center would be better for what I think you're doing. Put
the lights on the first switch, and a couple of 240V circuits and at
least one 120V circuits in the rest of the spaces. When you leave, turn
off all the breakers except #1.
Like I said, I can't see what you're doing from here and I'm making a
lot of assumptions.
The purpose of these switches is to put a power disconnect (set of switches)
up out of the way so that I don't have to worry about power going to tools
when I am not around. Honestly, it's not that inconvenient going to the
200amp panel to cut them off, but this was one of the ways that I learned to
respect tools and the power that feeds them and IMO, it's a quick and
convenient (I will do it) way to make sure the power is off to all machinery
prior to leaving the shop. Having a 9 year old son who is interested in
working on things, while he understands and respects the power tools, I feel
it's a small price to pay for an added level of security.
Each circuit will have two 20amp 250v single plug outlets. Depending on the
requirements of the new tablesaw, I might have to use a different outlet for
that plug. The largest motor will be between 3hp and 5hp (tablesaw), but
most are in the 1hp to 2hp range.
Additionally, all machinery will be on cord/plug into outlets that can be
pulled in an emergency.
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