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Thread: Beware of Poor Electrical Advice

  1. #1
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    Red face Beware of Poor Electrical Advice

    I just read some weekly e-tips from a Woodworking magazine /website and I'm quite disappointed in one of the tips offered. I wrote to the publisher, but do not expect a correction or feedback from them since they were not smart enough to avoid the subject matter to begin with. This particular tip concerned using a "smart strip" to start a router AND a shop vac at the same time. If you have not encountered this before, a "smart strip" looks like a standard power strip but there is a master outlet and a few "slave " outlets. Power is sent to the slave outlets when you turn on the device that is plugged into the master. Convenient for gear with a low amp draw not adding up to the total strip capacity of 15A.

    In this "quick tip" there was no mention of Amp draw or checking your devices and adding them up to see if the strip was made to handle this. All the information should be readily available on the manufacturer's plate on the tools and also molded into the strip itself. The two "smart strips" that I checked on were both rated 15 Amps. This strip might work for some cases, but it seems likely that, in most cases, the 15A rating would be surpassed by the cumulative ratings of tool and shop vac. A p-c 690, for example, is shown to pull 11A and many shop vacs pull 10-12A. The amp draw would be 22A for these two devices going through a "smart strip" rated for 15A. I suggest this is not smart at all. Several scenarios are possible: at least one could easily burn the power strip you just paid $20 for, or you could simultaneously damage the motors on the shop vac and the router and realize ten times that dollar amount in loss. If you are lucky, the circuit breaker would trip first. Don't rely on luck when it comes to electricity!

    I caution against piecemeal electrical advice for the "devil's in the details". All of the electrical information is readily available to you; you just need to be curious enough to find it. I use a convenience that works for me in my shop, but this may not work for many others. I plug my 1 hp dust collector into a remote-controlled outlet and clip the remote to a belt loop. I found a remote controlled outdoor outlet (think Christmas lights) with an Amp rating high enough to handle the dust collector amp draw but beware many such devices are only rated for half that! I have the outlet plugged into a different circuit than any of the stationary power tools so the 20A circuit rating is not surpassed with tool and vac both on. Additionally, I have read articles where some enterprising woodworkers use such a remote to flip a larger magnetic switch that can handle the amp draw of a large dust collector. That costs a few $$, but is a safe bet.

    When I built the shop, I ran two different circuits into many of the 4-square boxes so that I have duplex outlets side-by-side powered by different circuits. The same end can be accomplished by running a short extension cord from a different circuit to the tool or the shop vac, whichever is easier. Just be sure the cord is rated to handle the amp draw and allow for amp drop if you use a long cord (not recommended). I keep a 15 ft. 12/3 cord handy for saws, as well as a couple of 15 ft. 14/3 cords for sanders, etc.

    Again, everything is labeled, just use the information and your head (or calculator). Above all, be safe having fun!
    Last edited by Dennis McCullen; 03-16-2018 at 7:45 AM.

  2. #2
    Thanks for the heads up and the advice Dennis!
    Fred
    "All that is necessary for the triumph of evil is that good men do nothing."

    “If you want to know what a man's like, take a good look at how he treats his inferiors, not his equals.”

  3. #3
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    I know you mentioned it but wouldn’t the “smart strip” breaker kick in before anything really goes wrong?

    I’ve been using a power strip like that for years to power on my shop vac while using ROS’s and router table. I notice no change in power up (max amp draw) and have no breakers tripped.

    I’m not concerned about it, though I appreciate your detailed explanation.

  4. #4
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    I believe I saw that same stupid tip. It was actually part of an email sent out by one of the woodworking magazines.

  5. #5
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    Not unusual to run a big vac and a router at the same time on the same circuit using one of those smart i-socket vacuum switches. I do it all the time. Probably running near the limit of the breaker. 10 amp vac + 10 amp router with a 20 amp panel breaker. Vac could be pulling full amps, but you rarely load a router heavily.
    NOW you tell me...

  6. #6
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    You are right of course, BUT...
    There is a huge amount of slop on these things and you can routinely get away with things that aren't right. For instance; I bought a cottage that had a 23a water heater on #12 wire for 20 years without anything going wrong. I replaced it, but probably didn't have to.

  7. #7
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    Prbably has to do with less then 100% useage rules per NEC.
    Bill

  8. #8
    Well, I am not an electrician, but, I use a Bosch 1617 on a CNC router. I have it and all the CNC electronics running through a strip and that goes through a "box" I made with an amp meter. I have never seen it draw more than around 6A - even chugging through wood. A Kill-a-Watt device is a fun toy too - it can tell you exactly what is going on. At my old shop (garage), I always had whatever tool I was using and the shopvac on the same extension cord. Never had any issues. Never measured those.

    Tony

    This is without the router on...
    IMG_4515 (Small).JPG

  9. #9
    As an electrician with 35 years field experience, I am always amazed when I see people asking for help from those who are not professionals. When I was a first year apprentice we were shown grisly pictures of electricians who, unfortunately, experienced what can happen when you're not ever vigilant. The pictures were intended to scare the hell out of us so we would never take safety for granted. We were also taught how electricity can kill you. Those things were ingrained in my mind forever.

    Tips and tricks with electricity?
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

  10. #10
    I understand the concern... Fuses, circuit breakers, and power strips are all there to protect the wiring inside your house from overheating and catching the house on fire... The circuit breaker isn't there to be the Killjoy fun stopper....

    And heat buildup is a time/amps thing.. If you are running a 15 amp circuit at 14.8 amps for 6 hours straight - it may get pretty warm... The circuit breaker won't care, though...

    And YES - if I was a magazine editor, I don't want to go on record for publishing bad advice that could burn somebody's house down... Not a smart move...

    But the other end of this is you as the user seeing what your devices actually pull to verify you really are in the clear.. Most devices tend to pull very high loads at startup - so if the control unit sequences the starting of each thing by a few seconds - it won't whomp the system with a ton of amps all at once... The next thing is to understand your devices... Dust collectors and vacuums typically pull the highest load when the fan is running in free air - no bag, no housing, no hoses or ducts... Add all that junk back on and fan amps can go down quite a bit because the fan isn't moving much air.... Saws, sanders, and routers also typically pull pretty low loads until they are loaded up... And often we don't load them heavily because the quality of work goes down drastically...

    Tony has a great suggestion here about using a current monitor to see what you actually are pulling... It may be a surprise..

  11. #11
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    When i took welding as a night class the welders had nice digital meters showing the amps as the arc was burning. Problem was they were led meters and showed zero when the arc was not in use. In use the welding helmet did not allow the user to read the numbers. It did allow class members to watch the numbers as other people worked.
    Bill
    Last edited by Bill Dufour; 03-16-2018 at 11:01 PM.

  12. #12
    Quote Originally Posted by Julie Moriarty View Post
    As an electrician with 35 years field experience, I am always amazed when I see people asking for help from those who are not professionals.
    I don't trust or touch wire. I'm way too stupid. Luckily I'm close friends with a commercial electrician, but if you don't know how too do something and there's solid potential for dying for your ignorance, hire someone else to do it.

    Replace a cord end? No problem.
    Screw around in a 100 amp 480v control box? No flipping way. I'll be riding the lightning.

  13. #13
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    Am I the only person who has tripped a breaker cutting rails and stiles and using a big shop vac on the same circuit at the same time? If I load up my big ancient Hitachi M12V to the max with a big bit, it is going to draw 14 or 15 amps. You can see that with a Kill-A-Watt device. The thing about breakers is they are slow devices. You can draw twice the rated current for a minute or more and they won't open up. That is a fact that is easily verified by looking at trip curves. Most of the time, a router won't be running at full rated load for more than 20 or 30 seconds while a vacuum is running. I still don't think it is a good idea.

  14. #14
    Quote Originally Posted by Martin Wasner View Post
    I don't trust or touch wire. I'm way too stupid. Luckily I'm close friends with a commercial electrician, but if you don't know how too do something and there's solid potential for dying for your ignorance, hire someone else to do it.

    Replace a cord end? No problem.
    Screw around in a 100 amp 480v control box? No flipping way. I'll be riding the lightning.
    Of all the things I had to do during my career that made me really nervous, two things stand out. Changing out a 480V disconnect in live switchgear and hanging a transformer on a pole with 12kV inches from the top of my hardhat. Those two incidents caused my spacial awareness to go into overdrive and probably took some time off my life.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

  15. #15
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    Dennis
    My Fein vac works on the same principal. Any device plugged into the vacuum will start up the vacuum when it turned on. It's actually pretty common now a days.
    I can use the Fein with my Festool TS75, My sanders,and smaller routers, but not my Festool OF2200. That combination pops the breaker.

    "Newer" kitchen and dining room duplex receptacle strategy is kind of the same as your "two duplex receptacle strategy". You alternate the duplex receptacle circuits to not overload one circuit.
    The Smart Strips appear to have a resettable breaker built into them, so it shouldn't get any more dangerous than a normal power strip.
    Last edited by Mike Cutler; 03-18-2018 at 8:31 AM.

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