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  • Wiring to a machine in the middle of the floor

    my shop is a complete disaster right now. I decided to redo all the wiring. I had romex on exposed walls everywhere....never bothered me as I'm the only one in there, but still, its a safety issue and should be done right. The impetus was adding 600V to the mix, it has to be done right. Its such an awful job because it seems there's a 1000lbs of stuff to be moved for every section of conduit run, then there's a 1000 lbs of stuff to step over to run said section of conduit. this in a shop where you often have to turn sideways and follow the alleys just to get from side to side.

    anyway, several machines are in the middle of the floor. Trenching is not an option. Current plan is run emt on the ceiling to a box over top of the machine then install a receptacle and plug the machine in - seen this done in industry....or should i just wire the rubber cable to the machine right into the box. I don't need flexibility, but figured the plug was a bit of a safety device - if something hit the cable, it pulls out instead of pulling down the conduit?

    What type of plug to use? those big (expensive) twist lock ones? I thought even a range plug - cheap, plentiful, will give my three lines + a ground and is heavy it won't just fall out. Thing is I have 600V 3P, 240 3P and 240 single, while i'm the only one using them i don't what to set up a situation where someone plugs a 240 machine into a 600 plug.

    what great ideas do you guys have?
    .

  • #2
    A drop is the thing to do. The only issue is if it is going to interfere with usage..... as with a table saw, possibly. Then it may be an unacceptable hazard.

    Plugs are good, they form the required "disconnect", and are acceptable to any inspector as such. Otherwise you must put in a "formal" disconnect switch, with , if your shop is commercial in any sense, lockout/tagout provisions

    As for plugs, you can use ANY suitable plug, so long as you use it within its ratings, and so long as there is no other usage of that plug style in the facility (the formal rule requires no chance of confusing it with a different violtage).

    For a drop, a twist-lock type will obviously be best, and may be required by an inspector.
    1601

    Keep eye on ball.
    Hashim Khan

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    • #3
      I know the system used in the US & Canada is different to what we use here in Aus but isn't there some sort of std there that covers plugs & sockets.
      Here we have either Single Phase 240V or 3 phase 415V.
      240V plugs have 3 flat pins (active, neutral & earth) and only differ in that the most common, std, one is rated at 10amps, the next one is rated at 15amps and has a larger earth (ground) pin.( A 10 amp plug will plug into a 15amp socket, but a 15amp plug will not fit a 10amp socket) I believe there is also another which is 20amps with a larger earth pin again, though I have never seen one.
      For 415v the plug is a lot larger than the 240V and can have either 4 pins (3 active + neutral) or 5 pins (3 active, 1 neutral, 1 earth) The pins are round and there is a retaining ring on the plug that screws onto the socket once the plug is plugged in.
      415V plugs come in a range of different amperages and they are different sizes. its physically impossible to plug the wrong plug into a socket.

      best of luck with your rewire

      bollie7
      Last edited by bollie7; 04-24-2009, 10:22 AM.

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      • #4
        I would go with a drop also, so long as the plug style is rated for the amps and voltage, for a ceiling I would choose the twistlock as they are less likely to drop out or work loose from vibration and arc out, also less weight and bulk of a range or dryer plug, those might require you to mount the box on edge instead of flat being it's the ceiling or your cable would have a big arch to being they're intended for a wall mount, the code wants those boxes more rigidly mounted with studding in the wall also/surface mount not a problem, that and I had looked at the dryer cords and they really weren't that cheap at around 25-30 bucks each, they would do your 3 phase though.......

        I have left my entire RPC setup on a cart as it remains portable, temporary, and should someone ever inspect it all I have is some machines with a twistlock cord plug, a 50 amp 230V welder receptacle and a cart with cab-tire cable and funny lookin junk on it pushed off to a corner......with all the other crap it would right blend in......
        Last edited by hardtail; 04-24-2009, 11:25 AM.
        Opportunity knocks once, temptation leans on the doorbell.....

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        • #5
          Hubbbell wiring devices has fittings for all voltages. http://www.hubbell-wiring.com/htm/Industrial20Amp.htm
          Bob

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          • #6
            I'll admit that it's been about 12 years since I last was involved in wiring ceiling drops to code, but at that time the code (USA) required a strain relief so the hanging load wasn't on the cord.

            This was the preferred method for us:

            http://www.hubbell-wiring.com/htm/Industrial20Amp.htm

            I recommend it.

            Pete
            1973 SB 10K .
            BenchMaster mill.

            Comment


            • #7
              Use strain reliefs at the ceiling junction and have twist lock set at convienent level. This satisifies the disconnect and does not require a ladder or other means of accessing the plug. costs a little more, but you also have a lock-out
              tag-out means.

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              • #8
                I would use a drop as well. Make sure the receptacle is either above head height or well below where you will see it when the machine cable is unplugged. It's tempting to put at a height that will bash you in the head as you walk about looking down to avoid stepping on the floor contents...
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  I've got several drops like that, have had for years, and they have worked well for me.
                  Russ
                  Master Floor Sweeper

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                  • #10
                    Personally I hate the idea of cables etc hanging from the ceiling, they always seem to be a nuisance especially if you want to add something even temporarily at that position.

                    A more satisfactory solution in my mind is to fix a pole (a 3"x3" for example) between the floor and the ceiling then bring the fixed cabling down that and put appropriate recepticals on it, twice as many as you expect to use!

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                    • #11
                      They make a wire mesh deal that looks like a "Chinese finger trap" that is designed to grab SO cord (heavy rubber cord...on the order of 3/4" OD). The tail of this wire mesh device has a loop that is designed to be hung from say an eye bolt. The device strain relieves the cord and grabs it tight under its own weight. I found a couple of them surplus and intend to use them when I hang power down to several machines that sit in the center of my shop.

                      I intend to hard wire the machines in my case. The only plugs that won't unplug themselves under cord weight are twist locks...and as such, they don't do anything to prevent something getting ripped out...the only real reason for them in the first place. That's what the aforementioned item is for.

                      As for code, I find a disconnect at the machine more common in industry, and likely safer than trying to treat a twist-lock plug as some sort of safety item. I would hate to think of scrambling to unplug something in the event of a disaster. Better to just pull a lever. Fused disconnects are pretty popular on machines...and they give you the ability to fuse for motor protection....something your circuit breakers are not designed to do. They are there to protect the wiring.

                      Edit-- I do find the last poster's comments interesting. A pole goes all the way to the floor and guarantees that you have one more thing to dance around as you use the machine. You also then have to have wire from the pole to the additional machines. A wire hanging down, in the case of many machines, is totally above the work area and not subect to being even touched in use. I think of my vertical mill, for example, where the cable comes in to a switch box mounted on the head. A wire feeding that from the ceiling would be totally above my head and not subject to getting hit in use....unlike a pole going clear to the floor. It's probably different for different machines I guess...Paul
                      Last edited by pcarpenter; 04-24-2009, 06:16 PM.
                      Paul Carpenter
                      Mapleton, IL

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                      • #12
                        Originally posted by The Artful Bodger
                        Personally

                        A more satisfactory solution in my mind is to fix a pole (a 3"x3" for example) between the floor and the ceiling then bring the fixed cabling down that and put appropriate recepticals on it, twice as many as you expect to use!
                        i gotta go with this idea. even a 2x4 hanging part way from the ceiling is better than a just a cord. .

                        Comment


                        • #13
                          Originally posted by The Artful Bodger
                          Personally I hate the idea of cables etc hanging from the ceiling, they always seem to be a nuisance especially if you want to add something even temporarily at that position.

                          A more satisfactory solution in my mind is to fix a pole (a 3"x3" for example) between the floor and the ceiling then bring the fixed cabling down that and put appropriate recepticals on it, twice as many as you expect to use!
                          I appreciate your thoughts but how can a cord be more in the way than a post, permanent or temp? If he has a receptacle at ceiling level theres nothing in the way once unplugged.....

                          McGyver the cable requirements once your at 600V is going to be pretty light, likely 12 ga will suffice, the dryer/range stuff may not be 600V rated but the guage 8/10 will be more than likely required.
                          Opportunity knocks once, temptation leans on the doorbell.....

                          Comment


                          • #14
                            yeah, i wasn't going to use the dryer cord, just the plugs, want one style 4 prong for 220 and one for 600. I'm using 12gauge through out, 120/240/600....bought a 600V roll

                            all the machines have electrical boxes with the start stop switch, does that qualify as a disconnect or should there be the knife switch as well? then again they are all hooked up same was as in industry, ie on/off was this disconnect

                            on the safety aspect, i wasn't thinking that the plug would be use to turn the machine off in an emergency, more that in a crowded space if something hit it, it would be a lot better to have the plug come out than pulling a run of conduit down.

                            Paul, I know exactly what you mean, the chinese finger traps, have one somewhere that came with the XLO

                            after more thought, i think I'll try straight (not twist) plugs if i can find some variety. It would cheap, safe and i can see times with moving a sheet of plywood, big welded assembly or lengths of bar stock that it would handy to get the cords out of the way. Those twist ones are too expensive; I've got 4 to do. Permanent post takes up too much room....with the hanging cord, i can have it positioned right over the electrical box so the foot print isn't enlarged....with adding this old iron, I've got to think like a submariner

                            thanks for all the help
                            .

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                            • #15
                              Mcgyver, like it or not, you are bound by the Ontario Electrical Code, and somewhere in it will be found what you CAN do and what you are REQUIRED to do. I would think that you will have to install the specified plug for the service you require at that particular machine. For 600V 3 ph, there may be no male/female plug set, only a male plug and female outlet, in which case you will have to instal a column of some sort like Unistrut. Probably not what you wanted to hear, and at the same time, I doubt very much that the inspector will let you use a dryer or stove receptical for anything BUT a dryer or stove. Remember this, if your shop SHOULD be damaged by fire, the adjuster 's job is to see if there is ANY reason the insurer SHOULD NOT pay you. Duffy
                              Duffy, Gatineau, Quebec

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