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All 220 volt outlets are the same, right?

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Forum topic by bunkie posted 03-22-2011 04:07 PM 33861 views 3 times favorited 51 replies Add to Favorites Watch
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bunkie

412 posts in 2613 days


03-22-2011 04:07 PM

My shop occupies the same space as the laundry. We have an electric dryer. When I bought my cabinet saw, I went to big box store and got a plug that fit the dryer outlet. Problem solved!

I had an electrician in the other day to quote on various jobs. I mentioned that I wanted a quote on getting a 220V circuit as I’d like to have the outlet in a more convenient spot. He took a look at my saw and said “this is a 20 amp saw and you are using a 30 amp circuit”. The upshot is that the breaker is over-sized for use with the saw. In the greater scheme of things, the risk is probably pretty small. But it’s not zero. I always unplug the saw when it’s not in use, but it’s conceivable that I could forget.

So, I guess that the new circuit has risen to the top of the list of things to be done. A few weeks ago, the house across the street burned down. It wasn’t an electrical fire, but it surely focuses the mind on things that are best avoided.

-- Altruism is, ultimately, self-serving


51 replies so far

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Brrman

60 posts in 2139 days


#1 posted 03-22-2011 04:23 PM

I just recently added a couple of 20A 220v outlets to my shop. A dryer outlet/plug is not really what you want for that. You want some 12/2 wire, a 20A double breaker and something like this:

and this

-- "Being a perfectionist does not make one perfect..."

View HorizontalMike's profile

HorizontalMike

7155 posts in 2380 days


#2 posted 03-22-2011 04:38 PM

I used these plugs and outlets. They are locking and I find that assuring/safer. Oh yeah, I also used 10-3 armor clad from the box to the outlets PLUS changed out the 14-3 tool power cords to 12-3 power cords. If you want to call me anal, that should be Dr. Anal (PhD):

-- HorizontalMike -- "Woodpeckers understand..."

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Bertha

13003 posts in 2159 days


#3 posted 03-22-2011 05:13 PM

That amperage discrepancy would make me nervous but I’m not a sparky. I use the exact system as Mike above. Before I installed the locking plugs, I once had an offcut unplug my saw. That really got my attention.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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Alan S

178 posts in 2783 days


#4 posted 03-22-2011 06:10 PM

What risk would there by running a 20 amp saw on a 30 amp circuit?

Alan

View bunkie's profile

bunkie

412 posts in 2613 days


#5 posted 03-22-2011 06:15 PM

Conceivably, you could have a situation where the saw was stalled and was drawing, say, 28 amps which would overload the internal wiring of the saw without tripping the breaker causing eventual failure of the insulation which could lead to a fire.

A (hopefully) simple solution would be to wire in a 20 amp breaker and mount it inside the saw.

But the right thing to do is to get a proper circuit wired.

-- Altruism is, ultimately, self-serving

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Bertha

13003 posts in 2159 days


#6 posted 03-22-2011 06:16 PM

Again, not a sparky, but I would think that if the saw began to draw more than it’s 20A rating, there would be no tripping of the circuit. There are alot of electricians here. Maybe I’ll get educated.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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brtech

906 posts in 2389 days


#7 posted 03-22-2011 06:26 PM

Does the electrician want you to put 5A breakers on your outlet strings that now only have CFLs and laptops on them?

I think this is a very small problem. If you are really worried, sure, a new circuit with the right sized breaker is a fine solution. You can also have him install a sub panel, or even a simple fused disconnect between the dryer and the saw outlet. I’d just leave it. Or, even better – have him give you a couple of 110 outlets on the 220 circuit.

Horizontal Mike’s connectors are “Twist Locks” and they are used when you frequently plug and unplug the connection. The ones Brrman uses are fine for a connection that is roughly never disconnected.

Now, you obviously never run the dryer when you run the saw, right? If that is even a remote possibility, then you want a separate circuit for the saw.

View HorizontalMike's profile

HorizontalMike

7155 posts in 2380 days


#8 posted 03-22-2011 06:28 PM

Been +35yr since my sparky days, but I would think you should make sure your wiring is capable of handling the 30amp load. The breaker is there to FIRST save the wiring in the walls and SECOND to save the tool. A more current sparky can give you the specifics on wire loads for each size of wiring and length of each run.

Along those lines I probably should swap out my 50amp breaker (running 10-3 240v) to something smaller that matches my 30amp tools. Originally put the 50amp breaker in because it served two tools (but I only USE one at a time! DOAH!).

-- HorizontalMike -- "Woodpeckers understand..."

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RONFINCH

143 posts in 2391 days


#9 posted 03-22-2011 06:33 PM

Drawing less amps then your breaker can handle isn’t the problem. As Bunkie said, not tripping the breaker when drawing more than your machine is rated for is going to lead to burning up your equipment.

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Bertha

13003 posts in 2159 days


#10 posted 03-22-2011 06:33 PM

I imagine the saw probably has its own 20A breaker at the motor. I hadn’t considered that the breaker primarily insures the wiring, not the tool. See, I learned something.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View bunkie's profile

bunkie

412 posts in 2613 days


#11 posted 03-22-2011 06:38 PM

As I said, the risk is small. And, of course, any time you run a total load lower than the rated circuit breaker the same situation exists. For the record, he didn’t suggest 5A breakers ;-)

Since I have only one outlet for the dryer, I unplug it before plugging in the saw. So there’s no chance of popping the breaker while both ripping some oak and drying my shirts ;-)

I guess that my feeling is that accepting risks like this one is a slippery slope. I’ve been pretty lucky in my life with risks taken so far but I feel that, sooner or later, luck has a tendency to run out.

-- Altruism is, ultimately, self-serving

View devann's profile

devann

2202 posts in 2158 days


#12 posted 03-22-2011 06:44 PM

I’ve seen several different ones. Depends on the amps. Ask TopamaxSurvivor I sure he can tell you what you need.

-- Darrell, making more sawdust than I know what to do with

View Alan S's profile

Alan S

178 posts in 2783 days


#13 posted 03-22-2011 07:21 PM

This has come up before and I have been curious why people are worried about it. Breakers are meant to protect the wiring inside your walls from overheating and causing a fire. Breakers aren’t meant to protect equipment.

Honestly, I think choosing to have an electrician come out, who could possibly mess up his work and use the improper wire/breaker size, which could have the potential of causing a house fire, is a GREATER risk than running a 20 amp motor on a 30 amp circuit.

Alan

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Loren

8313 posts in 3114 days


#14 posted 03-22-2011 07:54 PM

Maybe you should get a second or third opinion from other
electricians. Guys who have their own wood and metal machinery
in their garages are probably gonna give you prudent advice.

And NO – not all 220 volt outlets are the same. You can wire your
220 with one type and your 110 with another and this prevents
you from plugging the wrong tool into the the wrong outlet.

View HorizontalMike's profile

HorizontalMike

7155 posts in 2380 days


#15 posted 03-22-2011 08:14 PM

Just as Alan has repeated part of what I mentioned earlier: Breakers protect house wiring FIRST and foremost, but an equally important point (and one I am also guilty of forgetting) is that breakers CAN HELP protect equipment when properly sized to each machine. Many/Most of our equipment has thermal overload protection built in (often in the magnetic switch). Beyond that, the key is to match as closely as possible the breaker with the machine amperage for an added layer of protection (or should I say preemptive damage control). The closer you get, the less you may damage your equipment if the built-in thermal protection fails. No guarantees here but you get the idea. Don’t bring a flame thrower to a wiener roasting contest…

-- HorizontalMike -- "Woodpeckers understand..."

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