The magnetic switch on my Jet DC-1100C dust collector is not very accessible. Will it damage the collector motor or circuitry to plug it into a power bar a few feet away and use the power bar switch for on-off control?
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Replies
If it's a true magnetic switch then I believe you'll find that you still have to use the magnetic switch to start the motor. A magnetic switch turns itself off anytime power is cut to the switch.
What's the current rating of the power bar and what kind of loads is it rated for? What is the current rating of the dust collector. I wouldn't be surprised if the switch on the power bar fails if you use it to turn the joiner off.
No. The switch on a power strip is not rated for motor loads. (Universal motors such as routers are fine.) If the dust collector is small enough to run from a power strip, then it also does not likely have a magnetic starter.
You could relocate the existing switch, or you could purchase a small motor contactor and make your own remote switch with push buttons.
It's probably easier to buy a remote starter. A receiver plugs in line with the collector, you just have to keep track of the remote. It's unlikely your switch is magnetic.
Beat it to fit / Paint it to match
The 1100 motor plate lists it as drawing 11 amps on a 115 circuit. While this is well under the 15 amps that most power strips are rated for, I'd still be hesitant to put my 1100 on one (I agree, the switch is a pain in the petutkas).
However, if you look in the various catalogs, or go down to Home Depot or Lowes, you'll see heavy duty power boxes that are marketed for power tools. I'd feel comfortable using one of those, as long as it's not on a long and light extension cord. I have two different ones in my shop. One is a Stanley, the other was from Lowe's, no name, but square with a heavy cord (12ga?) and metal-encased.
Try those rather than using the cheap ones we use for household stuff. A Long Ranger remote would be the ultimate solution, but not everyone can afford one.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Even though the full load amps of the motor is below the rating of the switch, inductive motors draw much more during startup, which is why most standard switches are not rated for starting motors. The arcing from startup will pit and/or fuse the contacts.Universal motors do not have this high startup current, so it is OK to use these for hand tools such as routers.
Is there a formula, say a percentage, that tells one what the current draw is at start-up?? I'm curious, because my table saw, which is rated at 18 amps, is on a 20 amp circuit.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
There is not an easy answer for that. In the first milisecond there could be a 25 or 30 amp draw, after one second it is probably down to 20 amps once it is running it might only draw 10 amps. Motors that start under load, like dust collectors and aircompressors, will pull a lot more amps for a longer time. Most breakers are too slow to trip for most of their rated loads. Some exceptions are large machines like wide belt sanders and 10 HP dust collectors which need special delayed interupt breakers.Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
Forestgirl,
Yes there is a formula to tell you this, but it is too complex for this discussion. There is an estimate, and I will come back to that in a minute. When an induction motor is not rotating, the only electrical resistance is the copper in the windings. This value is very low, just a few ohms, and is virtually a dead-short-circuit. As the motor begins to rotate, a magnetic field is created and this results in another type of resistance, called reactance. The value of the reactance is a function of the rpm of the motor, so the faster the motor turns, the higher the reactance becomes.
When the motor is not turning, this is called the Locked Rotor condition, and many motors will provide the locked rotor amperage on the nameplate. I am not positive of this value, but I believe it is typically about 4 to 5 times the maximum rated current of the motor. However, this ratio will be different for different motors and ratings.
Because the magnetic field is also what makes the rotor turn, this locked rotor condition exists for just a few milliseconds until the motor begins to rotate. Because a typical motor will achieve its normal speed in about 1 to 1-1/2 seconds, the current level in the motor will be an exponential decay (looks like a skateboard ramp) starting out very high and very steep, but dropping off almost vertically in the first few milliseconds and then gradually leveling off to the running amperage level.
Most circuit breakers are designed to not react within this first few milliseconds of operation, but if the condition exists for much longer, they will trip. If the timeframe is kept short enough, you can send a lighting bolt down a telephone wire without melting the wire. So even though the current levels are well above the rating of the wire, the wire is still safe because the timeframe is so short.
Regarding your tablesaw, even though the motor is rated at 18 amps, this is its maximum current draw when the motor is loaded to its maximum rated load. When idling, it will draw about 9 amps, and when under a heavy load where you begin to hear the motor slow down, it is still below the maximum rating. It is only when you hear the motor really bog down that it is operating at its maximum permissible level before being damaged.
The wire inside the motor is much smaller than the wire inside your house, but the reason why they (the windings) can sustain more current than the house wiring is because they are being cooled down with the fan of the motor.
Thanks for the info, Rick, every bit helps if for no other reason that to remind me I'm not an electrician, LOL. Going back to the original discussion, however heavy duty those construction-type power boxes look, I take it the metal in the switch contacts is the weak point? What about using a wall-switch controlled electric box to start and stop a DC?? Not a good idea, or OK??forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Yes, you can control a DC from a standard light switch so long as you understand that the switch may eventually fail. However, because the switch can fail in the ON position (won't shut off), this is not something I would do with any other type of tool besides a DC.As a matter of fact, I do have a 2-pole (240 volt) light switch controlling my own DC because I can't easily reach the factory On/Off switch. Even though this switch is a heavy-duty switch that you won't find at a home center, I know that eventually it will fail because it is not rated for motor duty (although this one is close).This was just a temporary setup until I got the time to install a motor contactor with low-voltage controls scattered around the shop.The original question was about using a power strip. Those contacts are very, very light duty, and would probably fuse within just a few power cycles.
Yes the metal contactors are the weak point. A heavy duty comercial grade light switch will be a lot better, but as stated earlier could posibly fail in the on position. But that is not very likely (take that for what its worth). You can get a cheep line voltage motor started for $5 at a good hardware store, or a farm store. It looks like a regular stitch but there is some kind of simple over load circuit in it.Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
Thanks for all the advice. I looks like the collector switch isn't trully magnetic after all - I stays in the "on" position even when the power supply is cut off. I ended up installing a decent quality standard 110v switched outlet from Home Depot and this works fine for now. From the discussion I assume the switch contacts will eventually burn out or fuse but in the meantime I'll be looking into a wireless remote system.
i'm pretty sure that a motor rating reflects it's maximum draw...so usually you are using far less than the 18 amps your motor is rated at...
I have for many years been using a remote RF outlet for my DC. It has a key chain type of control like a garage door opener, and is available from Home Depot (at least in Canada). I taped the control to an old magnetic security pass holder (the type that holds over your pocket and is held in place by a magnet on either side of the fold). I also have a rare earth magnet stuck in the wall near the shop door.
When I walk into my shop I hang the remote over the back pocket of my jeans and just reach back and give it a push to turn the DC on or off. When I leave the shop I stick the holder to the magnet by the door. The wall receptic has been working just fine for my smallish 110v DC
Pardon my begging the question. I would like, however, to emphasize the importance of understanding whether or not a given tool has a magnetic switch.To wit, I have a Powermatic table saw with a non-magnetic switch (as shipped). This is handy, as it permits the use of a pneumatic foot switch. *But* every table saw manufacturer (and many other tool makers) should be compelled to install only magnetic switches!!Consider the *danger.* What if you are using the saw (with the blade above table, of course), and the power goes out or you or someone or something unplugs the saw? What happens when (even though no one is at the saw switch) power is restored to the saw?Exactly!(Thanks for not writing that there's danger in operating any tool. I know. A misstart is a potentially, extremely hazardous event. Several hypotheticals should come to mind.)I suggest that a person always focus exclusively on what they are doing when triggering, turning on, or even plugging in a shop tool. jc
Here's a picture of a simlar power box to the one I have. The one pictured is a GFCI box, more expensive at $32, but it'll give you the idea:
View Image
At Lowe's, rated 15 amps, 12 gauge cord, on-off switch.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
That is a great product but that switch wasn't meant to start a motor. For $15 you can assemble a remote switch using stuff at Home Depot. By remote I do not mean remote control, just a wired switch that turns the DC on and off.Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
As Hammer1 mentioned, a remote switch would be a good idea. I just purchased one the other day from Woodcraft and after the first day of using it, I couldn't believe I waited that long to get one. Easy to use, just plug it into the wall and plug your dust collector into that. I think I shelled out about $40 for it.
I've had a remote starter on my DC-650 for a couple of years now and can't imagine not having one. One of the remotes hangs near the switch on the TS and the other one hangs on the wall near the workbench. IMO, it's the only way to fly. - lol
This might not be of much help, but a competent electrician should be able to wire the switch on the dust collector to start when the table saw is started. It'll cost you a bit, but you can't beat the convenience. Also it means you can't get into the habit of thinking "I'm only making a few cuts. I don't really need the dust collector" (we all do that. You know it's true.) If you intend to use it on more than one tool, I'm sure you could have it wired accordingly, but I'll bet the price would start to climb pretty quickly. If that is the case, you could just have the switch moved or extended, if you will, to a more convenient location.
Nat,
For what it's worth.
most d/c's do not have magnetis switches...the manufacturers typically use a switch that will remain in the on position when power is interupted...I woud guess that they do this to allow you to control the device with either a switched reciptacle or a low voltage controller...
as mentioned most "power strips" are not designed to handle the type of loads you would like to introduce...
if you have your DC in a fixed location you should probably just wire up a switched outlet dedicated to the DC....If you move your DC around to connect it to various machines I would follow the previously given advice to construct your own remote switch from electrical components you can get at home depot.
all you would need is about 2 feet of cord, a switch box and cover plate, a switch, a male cord end, and a female cord end. you could construct it to handle whatever load is required by using appropriately rated components...
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